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  • 1. Chaparro, M Pia
    et al.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Ivarsson, Anneli
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Lindgren, Urban
    Umeå University, Faculty of Social Sciences, Department of Geography and Economic History, Economic and social geography.
    Nilsson, Karina
    Umeå University, Faculty of Social Sciences, Department of Sociology.
    Koupil, Ilona
    Childhood family structure and women's adult overweight risk: A longitudinal study2017In: Scandinavian Journal of Public Health, ISSN 1403-4948, E-ISSN 1651-1905, Vol. 45, no 5, p. 511-519Article in journal (Refereed)
    Abstract [en]

    AIM: The aim of this study was to investigate whether women's adult overweight and obesity risk was associated with their childhood family structure, measured as their mothers' marital status history, during the women's first 18 years of life.

    METHODS: Using linked register data, we analyzed 30,584 primiparous women born in Sweden in 1975 who were between 19-35 years of age when their height and pre-pregnancy weight was recorded. The outcomes were women's overweight/obesity (body mass index (BMI) ≥ 25 kg/m(2)) and obesity (BMI ≥ 30 kg/m(2)) and the predictor was mothers' marital status history, which was summarized using sequence analysis. We carried out nested logistic regression models adjusting for women's age and maternal sociodemographic characteristics.

    RESULTS: Mothers' marital status history was summarized into six clusters: stable marriage, stable cohabitation, married then divorcing, cohabiting then separating, varied transitions, and not with father. In fully adjusted models and compared with women whose mothers belonged to the stable marriage cluster: (1) women whose mothers belonged to the other marital status clusters had higher odds of overweight/obesity (odds ratio (OR) ranging 1.15-1.19; p < 0.05); and (2) women whose mothers belonged to the stable cohabitation (OR = 1.31; 95% confidence interval (CI) = 1.14-1.52), cohabiting then separating (OR = 1.23; 95% CI = 1.01-1.49), varied transitions (OR = 1.24; 95% CI = 1.11-1.39), and not with father (OR = 1.24; 95% CI = 1.00-1.54) clusters had higher odds of obesity.

    CONCLUSIONS: Women whose mothers were not in stable marriage relationships had higher odds of being overweight or obese in adulthood. The finding that even women raised in the context of stable cohabitation had higher odds of being overweight or obese is intriguing as these relationships are socially accepted in Sweden.

  • 2.
    Chaparro, M Pia
    et al.
    Centre for Health Equity Studies (CHESS).
    Ivarsson, Anneli
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Koupil, Ilona
    Centre for Health Equity Studies (CHESS).
    Nilsson, Karina
    Umeå University, Faculty of Social Sciences, Department of Sociology.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Lindgren, Urban
    Umeå University, Faculty of Social Sciences, Department of Geography and Economic History.
    Regional inequalities in overweight and obesity among first-time pregnant women in Sweden, 1992–20102015In: 22nd European Congress on Obesity (ECO2015), Prague, Czech Republic, May 6-9, 2015: abstracts, S. Karger, 2015, Vol. 8: suppl 1, p. 119-119Conference paper (Refereed)
  • 3.
    Chaparro, M. Pia
    et al.
    Centre for Health Equity Studies (CHESS).
    Ivarsson, Anneli
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Koupil, Ilona
    Centre for Health Equity Studies (CHESS).
    Nilsson, Karina
    Umeå University, Faculty of Social Sciences, Department of Sociology.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Lindgren, Urban
    Umeå University, Faculty of Social Sciences, Department of Geography and Economic History.
    Regional inequalities in pre-pregnancy overweight and obesity in Sweden, 1992, 2000, and 20102015In: Scandinavian Journal of Public Health, ISSN 1403-4948, E-ISSN 1651-1905, Vol. 43, no 5, p. 534-539Article in journal (Refereed)
    Abstract [en]

    Aims: To investigate regional differences and time trends in women’s overweight and obesity in Sweden. Methods: Using datafrom the Swedish Medical Birth Register (women aged ⩾18 years, first pregnancy only) and the Total Population Registeraccessed through the Umeå SIMSAM Lab, age-standardized prevalence of pre-pregnancy overweight/obesity (BMI ⩾ 25 kg/m2) and obesity (BMI ⩾ 30 kg/m2) were estimated by county for the years 1992, 2000, and 2010. Maps were created usingArcMap v10.2.2 to display regional variations over time and logistic regression analyses were used to assess if the observedtrends were significant. Results: The prevalence of pre-pregnancy overweight/obesity and obesity increased significantly inall Swedish counties between 1992, and 2010. In 2010, Södermanland and Gotland exhibited the highest age-standardizedoverweight/obesity (39.7%) and obesity (15.1%) prevalence, respectively. The sharpest increases between 1992 and 2010were observed in Västerbotten for overweight/obesity (75% increase) and in Gotland for obesity (233% increase). Across theyears, Stockholm had the lowest prevalence of overweight/obesity (26.3% in 2010) and obesity (7.3% in 2010) and one ofthe least steep increases in prevalence of both between 1992 and 2010. Conclusions: Substantial regional differencesin pre-pregnancy overweight and obesity prevalence are apparent in Sweden. Further research should elucidatethe mechanisms causing these differences.

  • 4.
    Cipriano, Mariateresa
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Hammarsten, Peter
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Fowler, Christopher J
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Association between cannabinoid CB1 receptor expression and Akt signalling in prostate cancer2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 6, p. e65798-Article in journal (Refereed)
    Abstract [en]

    Background: In prostate cancer, tumour expression of cannabinoid CB1 receptors is associated with a poor prognosis. One explanation for this association comes from experiments with transfected astrocytoma cells, where a high CB receptor expression recruits the Akt signalling survival pathway. In the present study, we have investigated the association between CB1 receptor expression and the Akt pathway in a well-characterised prostate cancer tissue microarray.

    Methodology/Principal Findings: Phosphorylated Akt immunoreactivity (pAkt-IR) scores were available in the database. CB1 receptor immunoreactivity (CB1IR) was rescored from previously published data using the same scale as pAkt-IR. There was a highly significant correlation between CB1IR and pAkt-IR. Further, cases with high expression levels of both biomarkers were much more likely to have a more severe form of the disease at diagnosis than those with low expression levels. The two biomarkers had additive effects, rather than an interaction, upon disease-specific survival.

    Conclusions/Significance: The present study provides data that is consistent with the hypothesis that at a high CB1 receptor expression, the Akt signalling pathway becomes operative.

  • 5.
    Claeson, Anna-Sara
    et al.
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Gouveia-Figueira, Sandra
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Fowler, Christopher J.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Nording, Malin L.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Levels of oxylipins, endocannabinoids and related lipids in plasma before and after low-level exposure to acrolein in healthy individuals and individuals with chemical intolerance2017In: Prostaglandins, Leukotrienes and Essential Fatty Acids, ISSN 0952-3278, E-ISSN 1532-2823, Vol. 121, p. 60-67Article in journal (Refereed)
    Abstract [en]

    Oxylipins and endocannabinoids play important biological roles, including effects upon inflammation. It is not known whether the circulating levels of these lipids are affected by inhalation of the environmental pollutant acrolein. In the present study, we have investigated the consequences of low-level exposure to acrolein on oxylipin, endocannabinoid and related lipid levels in the plasma of healthy individuals and individuals with chemical intolerance (CI), an affliction with a suggested inflammatory origin. Participants were exposed twice (60 min) to heptane and a mixture of heptane and acrolein. Blood samples were collected before exposure, after and 24 h post-exposure. There were no overt effects of acrolein exposure on the oxylipin lipidome or endocannibinoids detectable in the bloodstream at the time points investigated. No relationship between basal levels or levels after exposure to acrolein and CI could be identified. This implicates a minor role of inflammatory mediators on the systemic level in CI.

  • 6. Feldman, Inna
    et al.
    Eurenius, Eva
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Häggstrom, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE).
    Sampaio, Filipa
    Lindkvist, Marie
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health. Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE).
    Pulkki-Brannstrom, Anni-Maria
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Ivarsson, Anneli
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Effectiveness and cost-effectiveness of the Salut Programme: a universal health promotion intervention for parents and children-protocol of a register-based retrospective observational study2016In: BMJ Open, ISSN 2044-6055, E-ISSN 2044-6055, Vol. 6, no 8, article id e011202Article in journal (Refereed)
    Abstract [en]

    Introduction: There is inadequate evidence for the effectiveness and cost-effectiveness of health promotion interventions. The Salut Programme aims to reach all parents and children in the Vasterbotten County of Sweden with a combination of health promotion interventions initiated during pregnancy and continued over the childhood period. This study protocol describes an effectiveness study and an economic evaluation study, where the ongoing Salut Programme is compared to care-as-usual over the periods of pregnancy, delivery and the child's first 2 years of life. Methods: A register-based retrospective observational study design will be used with existing data sources with respect to exposures and outcomes. Outcomes of interest are clustered at 3 points: around the child's birth, 1 month after the child's birth and 2 years after the child's birth. We will simulate an experiment by retrospectively identifying and comparing children and their parents in the geographical areas where the Salut Programme was implemented since 2006 and onwards, and the areas where the Programme was not implemented before 2009. Outcomes will be analysed and compared for the premeasure period, and the postmeasure period for both groups. Our analysis combines difference-in-difference estimation with matching. A complementary analysis will be carried out on the longitudinal subsample of mothers who gave birth at least once during each of the time periods. The economic evaluation aims to capture the wider societal costs and benefits of the Salut Programme for the first 2 years of the children's lives. Incremental costs will be compared with incremental health gains and the results will be presented as a cost-consequence analysis. Ethics and dissemination: The Regional Ethical Review Board in Umea has given clearance for the Salut Programme research (2010-63-31M). No individual's identity will be revealed when presenting results. This study will provide information that can guide decision-makers to allocate resources optimally.

  • 7.
    Gabrielsson, Linda
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Gouveia-Figueira, Sandra
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Alhouayek, Mireille
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Fowler, Christopher J.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    The anti-inflammatory compound palmitoylethanolamide inhibits prostaglandin and hydroxyeicosatetraenoic acid production by a macrophage cell line2017In: Pharmacology Research & Perspectives, ISSN 2052-1707, Vol. 5, no 2, article id UNSP e00300Article in journal (Refereed)
    Abstract [en]

    The anti-inflammatory agent palmitoylethanolamide (PEA) reduces cyclooxygenase (COX) activity in vivo in a model of inflammatory pain. It is not known whether the compound reduces prostaglandin production in RAW264.7 cells, whether such an action is affected by compounds preventing the breakdown of endogenous PEA, whether other oxylipins are affected, or whether PEA produces direct effects upon the COX-2 enzyme. RAW264.7 cells were treated with lipopolysaccharide and interferon-c to induce COX-2. At the level of mRNA, COX-2 was induced > 1000-fold following 24 h of the treatment. Coincubation with PEA (10 mu mol/L) did not affect the levels of COX-2, but reduced the levels of prostaglandins D-2 and E-2 as well as 11- and 15-hydroxyeicosatetraenoic acid, which can also be synthesised by a COX-2 pathway in macrophages. These effects were retained when hydrolysis of PEA to palmitic acid was blocked. Linoleic acidderived oxylipin levels were not affected by PEA. No direct effects of PEA upon the oxygenation of either arachidonic acid or 2-arachidonoylglycerol by COX-2 were found. It is concluded that in lipopolysaccharide and interferon-c-stimulated RAW264.7 cells, PEA reduces the production of COX-2-derived oxylipins in a manner that is retained when its metabolism to palmitic acid is inhibited.

  • 8.
    Gylling, Björn
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Myte, Robin
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Schneede, Jørn
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Hallmans, Göran
    Umeå University, Faculty of Medicine, Department of Biobank Research.
    Häggstrom, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Johansson, Ingegerd
    Umeå University, Faculty of Medicine, Department of Odontology.
    Ulvik, Arve
    Ueland, Per M.
    Van Guelpen, Bethany
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Palmqvist, Richard
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Vitamin B-6 and colorectal cancer risk: a prospective population-based study using 3 distinct plasma markers of vitamin B-6 status2017In: American Journal of Clinical Nutrition, ISSN 0002-9165, E-ISSN 1938-3207, Vol. 105, no 4, p. 897-904Article in journal (Refereed)
    Abstract [en]

    Background: Higher plasma concentrations of the vitamin B-6 marker pyridoxal 5#-phosphate (PLP) have been associated with reduced colorectal cancer (CRC) risk. Inflammatory processes, including vitamin B-6 catabolism, could explain such findings. Objective: We investigated 3 biomarkers of vitamin B-6 status in relation to CRC risk. Design: This was a prospective case-control study of 613 CRC cases and 1190 matched controls nested within the Northern Sweden Health and Disease Study (n = 114,679). Participants were followed from 1985 to 2009, and the median follow-up from baseline to CRC diagnosis was 8.2 y. PLP, pyridoxal, pyridoxic acid (PA), 3-hydroxykynurenine, and xanthurenic acids (XAs) were measured in plasma with the use of liquid chromatography-tandem mass spectrometry. We calculated relative and absolute risks of CRC for PLP and the ratios 3-hydroxykynurenine: XA (HK: XA), an inverse marker of functional vitamin B-6 status, and PA:(PLP + pyridoxal) (PAr), a marker of inflammation and oxidative stress and an inverse marker of vitamin B-6 status. Results: Plasma PLP concentrations were associated with a reduced CRC risk for the third compared with the first quartile and for PLP sufficiency compared with deficiency [OR: 0.60 (95% CI: 0.44, 0.81) and OR: 0.55 (95% CI: 0.37, 0.81), respectively]. HK: XA and PAr were both associated with increased CRC risk [OR: 1.48 (95% CI: 1.08, 2.02) and OR: 1.50 (95% CI: 1.10, 2.04), respectively] for the fourth compared with the first quartile. For HK: XA and PAr, the findings were mainly observed in study participants with,10.5 y of follow-up between sampling and diagnosis. Conclusions: Vitamin B-6 deficiency as measured by plasma PLP is associated with a clear increase in CRC risk. Furthermore, our analyses of novel markers of functional vitamin B-6 status and vitamin B-6-associated oxidative stress and inflammation suggest a role in tumor progression rather than initiation.

  • 9.
    Gylling, Björn
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Myte, Robin
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Ulvik, Arve
    Bevital AS, Laboratory building, Bergen, Norway.
    Ueland, Per Magne
    Department of Clinical Science, University of Bergen and Laboratory of Clinical Biochemistry, Haukeland University Hospital, Bergen, Norway.
    Midttun, Øivind
    Bevital AS, Laboratory building, Bergen, Norway.
    Schneede, Jørn
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Hallmans, Göran
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Nutritional Research.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Johansson, Ingegerd
    Umeå University, Faculty of Medicine, Department of Odontology.
    van Guelpen, Bethany
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Palmqvist, Richard
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    One-carbon metabolite ratios as functional B-vitamin markers and in relation to colorectal cancer risk2019In: International Journal of Cancer, ISSN 0020-7136, E-ISSN 1097-0215, Vol. 144, no 5, p. 68p. 947-956Article in journal (Other academic)
    Abstract [en]

    Background: One-carbon metabolism biomarker are easily measured in plasma, but analyzing them one at a time in relation to disease does not take into account the interdependence of the many factors involved. The relative dynamics of major one-carbon metabolism branches can be assessed by relating the functional B-vitamin marker total homocysteine (tHcy) to transsulfuration (total cysteine) and methylation (creatinine) outputs.

    Objective: We validated the ratios of tHcy to total cysteine (Hcy:Cys), tHcy to creatinine (Hcy:Cre), and tHcy to cysteine to creatinine (Hcy:Cys:Cre) as functional markers of B-vitamin status. We also calculated the associations of these ratios to colorectal cancer (CRC) risk.

    Design: The relative contribution of potential confounders to the variance of the ratio-based B-vitamin markers was calculated by linear regression in a nested case-control study of 613 CRC cases and 1211 matched controls. Total B-vitamin status was represented by a summary score comprising Z-standardized plasma concentrations of folate, cobalamin, betaine, pyridoxal 5´-phosphate, and riboflavin. Associations with CRC risk were estimated using conditional logistic regression.

    Results: The ratio-based B-vitamin markers all outperformed tHcy as markers of total B-vitamin status, in both CRC cases and controls. Associations with CRC risk were similar for the ratio-based B-vitamin markers and total B-vitamin status (approximately 25% lower risk for high versus low B-vitamin status).

    Conclusions: Ratio-based B-vitamin markers were good predictors of total B-vitamin status, and displayed similar associations with CRC risk. Since tHcy and creatinine are routinely clinically analyzed, Hcy:Cre could be easily implemented in clinical practice to aid interpretation of tHcy results.

  • 10.
    Hammarsten, Peter
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Winther, Johanna
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Rudolfsson, Stina H
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Urology and Andrology.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Karalija, Amar
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
    Egevad, Lars
    Department of Pathology and Cytology, Karolinska University Hospital, Stockholm.
    Granfors, Torvald
    Department of Urology, Central Hospital, Västerås, Sweden.
    Fowler, Christopher
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    ErbB2 Receptor Immunoreactivity in Prostate Cancer: Relationship to the Androgen Receptor, Disease Severity at Diagnosis and Disease Outcome2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 9, article id e105063Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: ErbB2 is a member of the epidermal growth factor family of tyrosine kinases that is centrally involved in the pathogenesis of prostate cancer and several studies have reported that a high expression of this protein has prognostic value. In the present study, we have investigated whether tumour ErbB2 immunoreactivity (ErbB2-IR) has clinically useful prognostic value, i.e. that it provides additional prognostic information to that provided by routine clinical tests (Gleason score, tumour stage).

    METHODOLOGY/PRINCIPAL FINDINGS: ErbB2-IR was measured in a well-characterised tissue microarray of tumour and non-malignant samples obtained at diagnosis. Additionally, mRNA levels of ErbB2-IR in the prostate were determined in the rat following manipulation of circulating androgen levels. Tumour ErbB2-IR was significantly associated with the downstream signalling molecule phosphorylated-Akt and with the cell proliferation marker Ki-67. The significant association of tumour ErbB2-IR with the Gleason score at diagnosis was lost when controlled for the association of both parameters with Ki-67. In the rat prostate, mRNA for ErbB2 was inversely associated with circulating androgen levels. There was no association between ErbB2-IR and the androgen receptor (AR)-IR in the tumours, but an interaction between the two parameters was seen with respect to their association with the tumour stage. Tumour ErbB2-IR was confirmed to be a prognostic marker for disease-specific survival, but it did not provide significant additive information to the Gleason score or to Ki-67.

    CONCLUSIONS/SIGNIFICANCE: It is concluded that tumour ErbB2-IR is of limited clinical value as a prognostic marker to aid treatment decisions, but could be of pathophysiological importance in prostate cancer.

  • 11.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Bandwidth selection for backfitting estimation of semiparametric additive modelsManuscript (preprint) (Other academic)
  • 12.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Bandwidth selection for backfitting estimation of semiparametric additive models: a simulation study2013In: Computational Statistics & Data Analysis, ISSN 0167-9473, E-ISSN 1872-7352, Vol. 62, p. 136-148Article in journal (Refereed)
    Abstract [en]

    A data-driven bandwidth selection method for backfitting estimation of semiparametric additive models, when the the parametric part is of main interest, is proposed. The proposed method is a double smoothing estimator of the mean-squared error of the backfitting estimator of the parametric terms. The performance of the proposed method is evaluated and compared with existing bandwidth selectors by means of a simulation study.

  • 13.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Data-driven Confounder Selection via Markov and Bayesian Networks2018In: Biometrics, ISSN 0006-341X, E-ISSN 1541-0420, Vol. 74, no 2, p. 389-398Article in journal (Refereed)
  • 14.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Rejoinder to Discussions on: Data-driven confounder selection via Markov and Bayesian networks2018In: Biometrics, ISSN 0006-341X, E-ISSN 1541-0420, Vol. 74, no 2, p. 407-410Article in journal (Other academic)
  • 15.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Selection of smoothing parameters with application in causal inference2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is a contribution to the research area concerned with selection of smoothing parameters in the framework of nonparametric and semiparametric regression. Selection of smoothing parameters is one of the most important issues in this framework and the choice can heavily influence subsequent results. A nonparametric or semiparametric approach is often desirable when large datasets are available since this allow us to make fewer and weaker assumptions as opposed to what is needed in a parametric approach. In the first paper we consider smoothing parameter selection in nonparametric regression when the purpose is to accurately predict future or unobserved data. We study the use of accumulated prediction errors and make comparisons to leave-one-out cross-validation which is widely used by practitioners. In the second paper a general semiparametric additive model is considered and the focus is on selection of smoothing parameters when optimal estimation of some specific parameter is of interest. We introduce a double smoothing estimator of a mean squared error and propose to select smoothing parameters by minimizing this estimator. Our approach is compared with existing methods.The third paper is concerned with the selection of smoothing parameters optimal for estimating average treatment effects defined within the potential outcome framework. For this estimation problem we propose double smoothing methods similar to the method proposed in the second paper. Theoretical properties of the proposed methods are derived and comparisons with existing methods are made by simulations.In the last paper we apply our results from the third paper by using a double smoothing method for selecting smoothing parameters when estimating average treatment effects on the treated. We estimate the effect on BMI of divorcing in middle age. Rich data on socioeconomic conditions, health and lifestyle from Swedish longitudinal registers is used.

  • 16.
    Häggström, Jenny
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Cipriano, Mariateresa
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Plym Forshell, Linus
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Persson, Emma
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Hammarsten, Peter
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Stella, Nephi
    Fowler, Christopher J.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Potential upstream regulators of cannabinoid receptor 1 signaling in prostate cancer: A Bayesian network analysis of data from a tissue microarray2014In: The Prostate, ISSN 0270-4137, E-ISSN 1097-0045, Vol. 74, no 11, p. 1107-1117Article in journal (Refereed)
    Abstract [en]

    BACKGROUND The endocannabinoid system regulates cancer cell proliferation, and in prostate cancer a high cannabinoid CB1 receptor expression is associated with a poor prognosis. Down-stream mediators of CB1 receptor signaling in prostate cancer are known, but information on potential upstream regulators is lacking. RESULTS Data from a well-characterized tumor tissue microarray were used for a Bayesian network analysis using the max-min hill-climbing method. In non-malignant tissue samples, a directionality of pEGFR (the phosphorylated form of the epidermal growth factor receptor) CB1 receptors were found regardless as to whether the endocannabinoid metabolizing enzyme fatty acid amide hydrolase (FAAH) was included as a parameter. A similar result was found in the tumor tissue, but only when FAAH was included in the analysis. A second regulatory pathway, from the growth factor receptor ErbB2 FAAH was also identified in the tumor samples. Transfection of AT1 prostate cancer cells with CB1 receptors induced a sensitivity to the growth-inhibiting effects of the CB receptor agonist CP55,940. The sensitivity was not dependent upon the level of receptor expression. Thus a high CB1 receptor expression alone does not drive the cells towards a survival phenotype in the presence of a CB receptor agonist. CONCLUSIONS The data identify two potential regulators of the endocannabinoid system in prostate cancer and allow the construction of a model of a dysregulated endocannabinoid signaling network in this tumor. Further studies should be designed to test the veracity of the predictions of the network analysis in prostate cancer and other solid tumors.

  • 17.
    Häggström, Jenny
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Data-driven smoothing parameter selection for estimating average treatment effectsManuscript (preprint) (Other academic)
  • 18.
    Häggström, Jenny
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Estimating prediction error: cross-validation vs. accumulated prediction error2010In: Communications in statistics. Simulation and computation, ISSN 0361-0918, E-ISSN 1532-4141, Vol. 39, no 5, p. 880-898Article in journal (Refereed)
    Abstract [en]

    We study the validation of prediction rules such as regression models and classification algorithms through two out-of-sample strategies, cross-validation and accumulated prediction error. We use the framework of Efron (1983) where measures of prediction errors are defined as sample averages of expected errors and show through exact finite sample calculations that cross-validation and accumulated prediction error yield different smoothing parameter choices in nonparametric regression. The difference in choice does not vanish as sample size increases.

  • 19.
    Häggström, Jenny
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Targeted smoothing parameter selection for estimating average causal effects2014In: Computational statistics (Zeitschrift), ISSN 0943-4062, E-ISSN 1613-9658, Vol. 29, no 6, p. 1727-1748Article in journal (Refereed)
    Abstract [en]

    The non-parametric estimation of average causal effects in observational studies often relies on controlling for confounding covariates through smoothing regression methods such as kernel, splines or local polynomial regression. Such regression methods are tuned via smoothing parameters which regulates the amount of degrees of freedom used in the fit. In this paper we propose data-driven methods for selecting smoothing parameters when the targeted parameter is an average causal effect. For this purpose, we propose to estimate the exact expression of the mean squared error of the estimators. Asymptotic approximations indicate that the smoothing parameters minimizing this mean squared error converges to zero faster than the optimal smoothing parameter for the estimation of the regression functions. In a simulation study we show that the proposed data-driven methods for selecting the smoothing parameters yield lower empirical mean squared error than other methods available such as, e.g., cross-validation.

  • 20.
    Häggström, Jenny
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Persson, Emma
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Waernbaum, Ingeborg
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    CovSel: An R Package for Covariate Selection When Estimating Average Causal Effects2015In: Journal of Statistical Software, ISSN 1548-7660, E-ISSN 1548-7660, Vol. 68, no 1, p. 1-20Article in journal (Refereed)
    Abstract [en]

    We describe the R package CovSel, which reduces the dimension of the covariate vector for the purpose of estimating an average causal effect under the unconfoundedness assumption. Covariate selection algorithms developed in De Luna, Waernbaum, and Richardson (2011) are implemented using model-free backward elimination. We show how to use the package to select minimal sets of covariates. The package can be used with continuous and discrete covariates and the user can choose between marginal co-ordinate hypothesis tests and kernel-based smoothing as model-free dimension reduction techniques.

  • 21.
    Häggström, Jenny
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Sampaio, Filipa
    Eurenius, Eva
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Pulkki-Brännström, Anni-Maria
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Ivarsson, Anneli
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Lindkvist, Marie
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    Feldman, Inna
    Is the Salut Programme an effective and cost-effective universal health promotion intervention for parents and their children?: a register-based retrospective observational study2017In: BMJ Open, ISSN 2044-6055, E-ISSN 2044-6055, Vol. 7, no 9, article id e016732Article in journal (Refereed)
    Abstract [en]

    OBJECTIVES: This study investigates the effectiveness and cost-effectiveness of the Salut Programme, a universal health promotion intervention, compared with care-as-usual, over the periods of pregnancy, delivery and the child's first 2 years of life.

    METHOD: We adopted a register-based retrospective observational design using existing data sources with respect to both exposures and outcomes. Health outcomes and costs were compared between geographical areas that received care-as-usual (non-Salut area) and areas where the programme was implemented (Salut area). We included mothers and their children from both the Salut and non-Salut areas if: (1) the child was born 2002-2004 (premeasure period) or (2) the child was born 2006-2008 (postmeasure period). The effectiveness study adopted two strategies: (1) a matched difference-in-difference analysis using data from all participants and (2) a longitudinal analysis restricted to mothers who had given birth twice, that is, both in the premeasure and postmeasure periods. The economic evaluation was performed from a healthcare and a limited societal perspective. Outcomes were clustered during pregnancy, delivery and birth and the child's first 2 years.

    RESULTS: Difference-in-difference analyses did not yield any significant effect on the outcomes. Longitudinal analyses resulted in significant positive improvement in Apgar scores, reflecting the newborn's physical condition, with more children having a normal Apgar score (1 min +3%, 5 min +1%). The cost of the programme was international dollar (INT$)308/child. From both costing perspectives, the programme yielded higher effects and lower costs than care-as-usual, being thus cost-saving (probability of around 50%).

    CONCLUSIONS: Our findings suggest that the Salut Programme is an effective universal intervention to improve maternal and child health, and it may be good value for money; however, there is large uncertainty around the cost estimates.

  • 22.
    Häggström, Jenny
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Westerlund, Olle
    Umeå University, Faculty of Social Sciences, Department of Economics.
    Norberg, Margareta
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Divorcing in middle age and its effects on BMIManuscript (preprint) (Other academic)
  • 23.
    Häggström, Jenny
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Wiberg, Marie
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Optimal Bandwidth Selection in Observed-Score Kernel Equating2014In: Journal of educational measurement, ISSN 0022-0655, E-ISSN 1745-3984, Vol. 51, no 2, p. 201-211Article in journal (Refereed)
    Abstract [en]

    The selection of bandwidth in kernel equating is important because it has a direct impact on the equated test scores. The aim of this article is to examine the use of double smoothing when selecting bandwidths in kernel equating and to compare double smoothing with the commonly used penalty method. This comparison was made using both an equivalent groups design and a nonequivalent group with anchor test design. The performance of the methods was evaluated through simulation studies using both symmetric and skewed score distributions. In addition, the bandwidth selection methods were applied to real data from a college admissions test. The results show that the traditional penalty method works well although double smoothing is a viable alternative because it performs reasonably well compared to the traditional method.

  • 24.
    Ju, Cheng
    et al.
    Division of Biostatistics, University of California, USA.
    Wyss, Richard
    Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Womens Hospital and Harvard Medical School, USA.
    Franklin, Jessica M
    Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Womens Hospital and Harvard Medical School, USA.
    Schneeweiss, Sebastian
    Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Womens Hospital and Harvard Medical School, USA.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    van der Laan, Mark J
    Division of Biostatistics, University of California, USA.
    Collaborative-controlled LASSO for constructing propensity score-based estimators in high-dimensional data2019In: Statistical Methods in Medical Research, ISSN 0962-2802, E-ISSN 1477-0334, Vol. 28, no 4, p. 1044-1063Article in journal (Refereed)
    Abstract [en]

    Propensity score-based estimators are increasingly used for causal inference in observational studies. However, model selection for propensity score estimation in high-dimensional data has received little attention. In these settings, propensity score models have traditionally been selected based on the goodness-of-fit for the treatment mechanism itself, without consideration of the causal parameter of interest. Collaborative minimum loss-based estimation is a novel methodology for causal inference that takes into account information on the causal parameter of interest when selecting a propensity score model. This “collaborative learning” considers variable associations with both treatment and outcome when selecting a propensity score model in order to minimize a bias-variance tradeoff in the estimated treatment effect. In this study, we introduce a novel approach for collaborative model selection when using the LASSO estimator for propensity score estimation in high-dimensional covariate settings. To demonstrate the importance of selecting the propensity score model collaboratively, we designed quasi-experiments based on a real electronic healthcare database, where only the potential outcomes were manually generated, and the treatment and baseline covariates remained unchanged. Results showed that the collaborative minimum loss-based estimation algorithm outperformed other competing estimators for both point estimation and confidence interval coverage. In addition, the propensity score model selected by collaborative minimum loss-based estimation could be applied to other propensity score-based estimators, which also resulted in substantive improvement for both point estimation and confidence interval coverage. We illustrate the discussed concepts through an empirical example comparing the effects of non-selective nonsteroidal anti-inflammatory drugs with selective COX-2 inhibitors on gastrointestinal complications in a population of Medicare beneficiaries.

  • 25.
    Myte, Robin
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Gylling, Björn
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Häggström, Christel
    Umeå University, Faculty of Medicine, Department of Biobank Research. Department of Surgical Sciences, Uppsala University, Uppsala, Sweden..
    Zingmark, Carl
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Löfgren Burström, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Palmqvist, Richard
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    van Guelpen, Bethany
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology. Umeå University, Faculty of Medicine, Wallenberg Centre for Molecular Medicine at Umeå University (WCMM).
    Metabolic factors and the risk of colorectal cancer by KRAS and BRAF mutation status2019In: International Journal of Cancer, ISSN 0020-7136, E-ISSN 1097-0215, Vol. 145, no 2, p. 327-337Article in journal (Refereed)
    Abstract [en]

    Factors related to energy metabolism and the metabolic syndrome, such as higher body mass index (BMI), blood glucose, or blood lipids, and blood pressure, are associated with an increased risk of colorectal cancer (CRC). However, CRC is a heterogeneous disease, developing through distinct pathways with differences in molecular characteristics and prognosis, and possibly also in risk factors. For subtypes defined by KRAS and BRAF mutation status, BMI is the only metabolic factor previously studied, with inconsistent findings. We investigated whether associations between BMI, blood glucose, blood lipids, and blood pressure and CRC risk differed by tumor KRAS and BRAF mutation status in 117,687 participants from two population-based cohorts within the Northern Sweden Health and Disease Study (NSHDS). Hazard ratios (HRs) for overall CRC and CRC subtypes by metabolic factors were estimated with Cox proportional hazards regression, using multiple imputation to handle missing exposure and tumor data. During a median follow-up of 15.6 years, we acquired 1,250 prospective CRC cases, of which 766 cases had complete baseline and molecular tumor data. Consistent with previous evidence, higher BMI, total cholesterol, triglyceride levels, and blood pressure were associated with an increased risk of overall CRC (HRs per 1 standard deviation increase: 1.07 to 1.12). These associations were similar regardless of CRC subtype by KRAS and BRAF mutation status (all pheterogeneity > 0.05). The same was true for subtypes based on microsatellite instability status. Poor metabolic health may therefore be a universal mechanism for colorectal cancer, acting across multiple developmental pathways.

  • 26.
    Myte, Robin
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Gylling, Björn
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Schneede, Jörn
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Löfgren-Burström, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Huyghe, Jeroen R.
    Hallmans, Göran
    Umeå University, Faculty of Medicine, Department of Biobank Research. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Nutritional Research.
    Meyer, Klaus
    Johansson, Ingegerd
    Umeå University, Faculty of Medicine, Department of Odontology.
    Ueland, Per Magne
    Palmqvist, Richard
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Van Guelpen, Bethany
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    One-carbon metabolism biomarkers and genetic variants in relation to colorectal cancer risk by KRAS and BRAF mutation status2018In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 13, no 4, article id e0196233Article in journal (Refereed)
    Abstract [en]

    Disturbances in one-carbon metabolism, intracellular reactions involved in nucleotide synthesis and methylation, likely increase the risk of colorectal cancer (CRC). However, results have been inconsistent. To explore whether this inconsistency could be explained by intertumoral heterogeneity, we evaluated a comprehensive panel of one-carbon metabolism biomarkers and some single nucleotide polymorphisms (SNPs) in relation to the risk of molecular subtypes of CRC defined by mutations in the KRAS and BRAF oncogenes. This nested case-control study included 488 CRC cases and 947 matched controls from two population-based cohorts in the Northern Sweden Health and Disease Study. We analyzed 14 biomarkers and 17 SNPs in prediagnostic blood and determined KRAS and BRAF mutation status in tumor tissue. In a multivariate network analysis, no variable displayed a strong association with the risk of specific CRC subtypes. A non-synonymous SNP in the CTH gene, rs1021737, had a stronger association compared with other variables. In subsequent univariate analyses, participants with variant rs1021737 genotype had a decreased risk of KRAS-mutated CRC (OR per allele = 0.72, 95% CI = 0.50, 1.05), and an increased risk of BRAF-mutated CRC (OR per allele = 1.56, 95% CI = 1.07, 2.30), with weak evidence for heterogeneity (Pheterogeneity = 0.01). This subtype-specific SNP association was not replicated in a case-case analysis of 533 CRC cases from The Cancer Genome Atlas (P = 0.85). In conclusion, we found no support for clear subtype-specific roles of one-carbon metabolism biomarkers and SNPs in CRC development, making differences in CRC molecular subtype distributions an unlikely explanation for the varying results on the role of one-carbon metabolism in CRC development across previous studies. Further investigation of the CTH gene in colorectal carcinogenesis with regards to KRAS and BRAF mutations or other molecular characteristics of the tumor may be warranted.

  • 27.
    Myte, Robin
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Gylling, Björn
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Schneede, Jörn
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Ueland, Per Magne
    Hallmans, Göran
    Umeå University, Faculty of Medicine, Department of Biobank Research. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Nutritional Research.
    Johansson, Ingegerd
    Umeå University, Faculty of Medicine, Department of Odontology.
    Palmqvist, Richard
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Van Guelpen, Bethany
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Untangling the role of one-carbon metabolism in colorectal cancer risk: a comprehensive Bayesian network analysis2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 43434Article in journal (Refereed)
    Abstract [en]

    The role of one-carbon metabolism (1CM), particularly folate, in colorectal cancer (CRC) development has been extensively studied, but with inconclusive results. Given the complexity of 1CM, the conventional approach, investigating components individually, may be insufficient. We used a machine learning-based Bayesian network approach to study, simultaneously, 14 circulating one-carbon metabolites, 17 related single nucleotide polymorphisms (SNPs), and several environmental factors in relation to CRC risk in 613 cases and 1190 controls from the prospective Northern Sweden Health and Disease Study. The estimated networks corresponded largely to known biochemical relationships. Plasma concentrations of folate (direct), vitamin B6 (pyridoxal 5-phosphate) (inverse), and vitamin B2 (riboflavin) (inverse) had the strongest independent associations with CRC risk. Our study demonstrates the importance of incorporating B-vitamins in future studies of 1CM and CRC development, and the usefulness of Bayesian network learning for investigating complex biological systems in relation to disease.

  • 28.
    Myte, Robin
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Gylling, Björn
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Schneede, Jörn
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Pharmacology.
    Ueland, Per Magne
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Hultdin, Johan
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Clinical chemistry.
    Hallmans, Göran
    Umeå University, Faculty of Medicine, Department of Biobank Research. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Nutritional Research.
    Johansson, Ingegerd
    Umeå University, Faculty of Medicine, Department of Odontology.
    Palmqvist, Richard
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Van Guelpen, Bethany
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Components of One-carbon Metabolism Other than Folate and Colorectal Cancer Risk2016In: Epidemiology, ISSN 1044-3983, E-ISSN 1531-5487, Vol. 27, no 6, p. 787-796Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Despite extensive study, the role of folate in colorectal cancer remains unclear. Research has therefore begun to address the role of other elements of the folate-methionine metabolic cycles. This study investigated factors other than folate involved in one-carbon metabolism, i.e., choline, betaine, dimethylglycine, sarcosine, and methionine and relevant polymorphisms, in relation to the risk of colorectal cancer in a population with low intakes and circulating levels of folate.

    METHODS: This was a prospective case-control study of 613 case subjects and 1,190 matched control subjects nested within the population-based Northern Sweden Health and Disease Study. We estimated odds ratios (OR) by conditional logistic regression, and marginal risk differences with weighted maximum likelihood estimation using incidence data from the study cohort.

    RESULTS: Higher plasma concentrations of methionine and betaine were associated with modest colorectal cancer risk reductions (OR [95% confidence interval {CI}] for highest versus lowest tertile: 0.76 [0.57, 0.99] and 0.72 [0.55, 0.94], respectively). Estimated marginal risk differences corresponded to approximately 200 fewer colorectal cancer cases per 100,000 individuals on average. We observed no clear associations between choline, dimethylglycine, or sarcosine and colorectal cancer risk. The inverse association of methionine was modified by plasma folate concentrations (OR [95% CI] for highest/lowest versus lowest/lowest tertile of plasma methionine/folate concentrations 0.39 [0.24, 0.64], Pinteraction = 0.06).

    CONCLUSIONS: In this population-based, nested case-control study with a long follow-up time from baseline to diagnosis (median: 8.2 years), higher plasma concentrations of methionine and betaine were associated with lower colorectal cancer risk. See Video Abstract at http://links.lww.com/EDE/B83.

  • 29.
    Myte, Robin
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology. Umeå University.
    Harlid, Sophia
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Sundkvist, Anneli
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Gylling, Björn
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Zingmark, Carl
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology. Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Löfgren Burström, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Palmqvist, Richard
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    van Guelpen, Bethany
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology. Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Metabolic biomarkers and the risk of molecular subtypes of colorectal cancerManuscript (preprint) (Other academic)
    Abstract [en]

    Background: Body fatness measured as high body mass index (BMI) increase the risk for colorectal cancer (CRC). The mechanisms behind the relationship are not fully understood, but might include insulin resistance and changes in adipokine concentrations produced by adipose tissue. Yet, associations between circulating biomarkers related to these mechanisms and CRC risk have been somewhat inconsistent, possibly due to CRC heterogeneity. To better understand the role of insulin resistance and adipokines in CRC development, we therefore investigated circulating biomarkers related to these mechanisms in relation to molecular subtypes of CRC.

    Methods: This was a prospective case-control study of 1010 cases and 1:1 matched controls nested within the population-based Northern Sweden Health and Disease Study (NSHDS). Concentrations of insulin, C-peptide, adiponectin, and leptin were quantified in prediagnostic plasma using immunoassays and related to CRC and CRC subtypes defined by mutations in BRAF and KRAS, and microsatellite instability (MSI) status analyzed in tumor tissue. Odds ratios (ORs) and 95% confidence intervals (CIs) for CRC by metabolic biomarker levels were calculated with conditional logistic regression.

    Results: Higher C-peptide and lower adiponectin were associated with an increased CRC risk (ORs per 1 standard deviation increase (95% CI): 1.11 (1.01, 1.23) and 0.91 (0.83, 1.00), respectively). The associations were attenuated when adjusting for BMI (ORs (95% CI): 1.07 (0.96, 1.19) and 0.93 (0.84, 1.03), respectively), with the potential exception of the association of C-peptide in women. Circulating insulin and leptin were not associated with CRC risk. We found no clear differences in the association between any biomarkers and CRC risk by molecular subtypes defined by KRAS and BRAF mutation status (Pheterogeneity>0.6), or MSI status (Pheterogeneity>0.3).

    Conclusion: Circulating biomarkers of insulin resistance and adipokines were not associated with CRC or specific molecular subtypes of CRC defined by KRAS and BRAF mutation or MSI status.

  • 30.
    Persson, Emma
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Waernbaum, Ingeborg
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    de Luna, Xavier
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Data-driven algorithms for dimension reduction in causal inference2017In: Computational Statistics & Data Analysis, ISSN 0167-9473, E-ISSN 1872-7352, Vol. 105, p. 280-292Article in journal (Refereed)
    Abstract [en]

    In observational studies, the causal effect of a treatment may be confounded with variables that are related to both the treatment and the outcome of interest. In order to identify a causal effect, such studies often rely on the unconfoundedness assumption, i.e., that all confounding variables are observed. The choice of covariates to control for, which is primarily based on subject matter knowledge, may result in a large covariate vector in the attempt to ensure that unconfoundedness holds. However, including redundant covariates can affect bias and efficiency of nonparametric causal effect estimators, e.g., due to the curse of dimensionality. In this paper, data-driven algo- rithms for the selection of sufficient covariate subsets are investigated. Under the assumption of unconfoundedness we search for minimal subsets of the covariate vector. Based on the framework of sufficient dimension reduction or kernel smoothing, the algorithms perform a backward elim- ination procedure testing the significance of each covariate. Their performance is evaluated in simulations and an application using data from the Swedish Childhood Diabetes Register is also presented.

  • 31.
    Wallin, Gabriel
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Häggström, Jenny
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Wiberg, Marie
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    How to select the bandwidth in kernel equating: an evaluation of five different methods2018In: Quantitative psychology: the 82nd annual meeting of the Psychometric Society, Zurich, Switzerland, 2017 / [ed] Marie Wiberg, Steven Culpepper, Rianne Janssen, Jorge González, Dylan Molenaar, Cham, Switzerland: Springer, 2018, p. 91-100Chapter in book (Refereed)
    Abstract [en]

    When using kernel equating to equate two test forms, a bandwidth needs to be selected. The bandwidth parameter determines the smoothness of the continuized score distributions and has been shown to have a large effect on the kernel density estimate. There are a number of suggested criteria for selecting the bandwidth, and currently four of them have been implemented in kernel equating. In this paper, all four of the existing bandwidth selectors suggested for kernel equating are evaluated and compared against each other using real test data together with a new criterion that implements leave-one-out cross-validation. Although the bandwidth methods generally were similar in terms of equated scores, there were potentially important differences in the upper part of the score scale where critical admission decisions are typically made.

1 - 31 of 31
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