Umeå University's logo

INTRODUCTION: Alzheimer's disease (AD) is a genetically heterogeneous disease, with various genetic variants potentially influencing disease mechanisms differently. Pathway-based polygenic risk scores (p-PRS) can be used to examine how groups of risk genes with similar biological functions impact disease-related endophenotypes such as cognitive decline. potentially aiding in differentiating pre-clinical dementia from normal age-related cognitive decline.

METHODS: Data from 1,737 participants (53.5% female) from the Betula study were analyzed. AD-weighted p-PRS were calculated for five AD-related pathways: immune response, tau, cholesterol, protein–lipid, and amyloid. The p-PRS were tested for associations with all-cause dementia risk (n = 315 cases), with follow-up analyses restricted to AD (n = 168) or vascular dementia (VD) (n = 110), in comparison to a genome-wide (gw) PRS. Linear mixed effect models were used to examine the same genetic predictors in relation to cognitive decline in subsequently demented and non-demented.

RESULTS: All-cause dementia risk was significantly predicted by the gw- and immune PRS. Hazard ratios for gw-, immune-, tau-, cholesterol-, and amyloid p-PRS were larger for prediction of AD risk and smaller for VD risk relative to all-cause dementia, while the opposite was seen for the protein–lipid p-PRS. Cognitive decline was stronger associated with the immune p-PRS than the gw-PRS, and this effect was driven by participants that remained non-demented (linear age-effects). Amyloid p-PRS showed accelerated age-effect at the oldest age in both non-demented and subsequently demented.

DISCUSSION: Our results show that AD-weighted p-PRS have differential roles on dementia risk and cognitive decline. Specifically, results suggest a broad role of immune p-PRS in both age-related cognitive decline and dementia risk, while amyloid p-PRS influences AD risk and pre-clinical cognitive decline, and protein-lipid p-PRS does not influence AD risk nor cognitive decline but show a potential role in VD. Results are of value for development of precision medicine based on genetic risk profiling. Highlights: All-cause dementia and Alzheimer's disease (AD) risk is strongest predicted by apolipoprotein E (APOE) ε4 and global polygenic risk scores (PRS). Cognitive decline is stronger predicted by immune pathway-based PRS (p-PRS) relative to global PRS. Effect of APOE ε4 on cognitive decline is driven by pre-clinical dementia. Immune p-PRS predicts cognitive decline unrelated to subsequent dementia. Protein–lipid p-PRS may have a stronger role in vascular dementia than AD.

Air pollution is increasingly discussed as a risk factor for dementia, but the biological mechanisms are not yet fully understood. Biological markers like telomere length are relevant to study with air pollution, as they are associated with aging and dementia. The study aimed to investigate the relationship between source-specific air pollution exposure and telomere length in a low-level air pollution area, and whether this potential relationship depended on future dementia status. The data originated from the Betula study in Northern Sweden, where 509 participants recruited between 1988 and 1995 were included to investigate the association between annual mean air pollution concentrations at the participants’ residences and relative leukocyte telomere length using a linear regression model. No association was observed between air pollution and telomere length, with regression slope estimates close to zero and p-values > 0.10 (e.g. PM2.5_total: β = 0.01 (-0.011, 0.025) and BC_total: β = 0.03 (95% CI: -0.046, 0.114). There were indications of a positive association between longer telomere length and higher exposure to air pollution among individuals later diagnosed with dementia (N = 74), but these findings were not conclusive (p-values > 0.10) (PM2.5_total: β = 0.03, p-value = 0.12; BC_total: β = 0.11, p-value = 0.17). Although not statistically significant, our findings contribute to the evidence from low-exposure settings, and it is important to report these types of findings for a balanced understanding of potential health effects.

Bipolar disorder is a heritable mental illness with complex etiology. While the largest published genome-wide association study identified 64 bipolar disorder risk loci, the causal SNPs and genes within these loci remain unknown. We applied a suite of statistical and functional fine-mapping methods to these loci and prioritized 17 likely causal SNPs for bipolar disorder. We mapped these SNPs to genes and investigated their likely functional consequences by integrating variant annotations, brain cell-type epigenomic annotations, brain quantitative trait loci and results from rare variant exome sequencing in bipolar disorder. Convergent lines of evidence supported the roles of genes involved in neurotransmission and neurodevelopment, including SCN2A, TRANK1, DCLK3, INSYN2B, SYNE1, THSD7A, CACNA1B, TUBBP5, FKBP2, RASGRP1, FURIN, FES, MED24 and THRA among others in bipolar disorder. These represent promising candidates for functional experiments to understand biological mechanisms and therapeutic potential. Additionally, we demonstrated that fine-mapping effect sizes can improve performance of bipolar disorder polygenic risk scores across diverse populations and present a high-throughput fine-mapping pipeline.

Bipolar disorder is a leading contributor to the global burden of disease. Despite high heritability (60–80%), the majority of the underlying genetic determinants remain unknown. We analysed data from participants of European, East Asian, African American and Latino ancestries (n = 158,036 cases with bipolar disorder, 2.8 million controls), combining clinical, community and self-reported samples. We identified 298 genome-wide significant loci in the multi-ancestry meta-analysis, a fourfold increase over previous findings, and identified an ancestry-specific association in the East Asian cohort. Integrating results from fine-mapping and other variant-to-gene mapping approaches identified 36 credible genes in the aetiology of bipolar disorder. Genes prioritized through fine-mapping were enriched for ultra-rare damaging missense and protein-truncating variations in cases with bipolar disorder, highlighting convergence of common and rare variant signals. We report differences in the genetic architecture of bipolar disorder depending on the source of patient ascertainment and on bipolar disorder subtype (type I or type II). Several analyses implicate specific cell types in the pathophysiology of bipolar disorder, including GABAergic interneurons and medium spiny neurons. Together, these analyses provide additional insights into the genetic architecture and biological underpinnings of bipolar disorder.

Bipolar disorder (BD) is a highly heritable mental disorder that affects millions of people worldwide. Our understanding of the genetic etiology and biological processes that underlie BD have greatly increased in recent years. Extensive progress has been made in identifying common variant signals for BD, and the polygenic score from the latest genome-wide association study (GWAS) may provide some clinical utility if combined with other risk factors for BD. The role of rare variation in BD remains to be determined, although genes annotated to common variant loci are shown to be enriched for rare variation. BD subtypes have been shown to differ in their genetic architecture, and as such, genetic studies across the subtypes of the BD spectrum will identify subtype-specific signals and reveal subtype-specific biological mechanisms. Despite this, subtype-specific GWAS sample sizes have not increased at the same rate as BD cases, and more concerted efforts are required to obtain this information for participants included in future BD GWASs. Moreover, assessment of culture, geography, and other systematic differences that may impact patient assessment will be necessary to ensure accurate inclusion of diverse ancestral groups and global representation in genetic studies of BD moving forward.

Introduction: Personality traits and neuropsychiatric symptoms such as neuroticism and depression share genetic overlap and have both been identified as risks factors for development of aging-related neurocognitive decline and Alzheimer’s disease (AD). This study aimed to examine revised personality factors derived from the Temperament and Character Inventory, previously shown to be associated with psychiatric disorders, as predictors of neuropsychiatric, cognitive, and brain trajectories of participants from a population-based aging study.

Methods: Mixed-effect linear regression analyses were conducted on data for the full sample (Nmax = 1,286), and a healthy subsample not converting to AD-dementia during 25-year follow-up (Nmax = 1,145), complemented with Cox proportional regression models to determine risk factors for conversion to clinical AD.

Results: Two personality factors, Closeness to Experience (CE: avoidance of new stimuli, high anxiety, pessimistic anticipation, low reward seeking) and Tendence to Liabilities (TL: inability to change, low autonomy, unaware of the value of their existence) were associated with higher levels of depressive symptoms, stress (CE), sleep disturbance (TL), as well as greater decline in memory, vocabulary and verbal fluency in the full sample. Higher CE was additionally associated with greater memory decline across 25 years in the healthy subsample, and faster right hippocampal volume reduction across 8 years in a neuroimaging subsample (N = 216). Most, but not all, personality-cognition associations persisted after controlling for diabetes, hypertension and cardiovascular disease. Concerning risks for conversion to AD, higher age, and APOE-ε4, but none of the personality measures, were significant predictors.

Conclusion: The results indicate that personality traits associated with psychiatric symptoms predict accelerated age-related neurocognitive declines even in the absence of neurodegenerative disease. The attenuation of some personality effects on cognition after adjustment for health indicators suggests that those effects may be partly mediated by somatic health. Taken together, the results further emphasize the importance of personality traits in neurocognitive aging and underscore the need for an integrative (biopsychosocial) perspective of normal and pathological age-related cognitive decline.

Today, adult individuals must be able to continuously learn and adapt to the rapid changes occurring in society. However, little is known about the individual characteristics, particularly personality traits, that make adults more likely to engage in learning activities. Moreover, few studies have longitudinally and objectively investigated the influence of personality on engagement in lifelong learning throughout working age. This study therefore used longitudinal data (15 years) to examine which personality traits predicted level and long-term changes in learning activities among 1329 Swedish adults aged 30–60. The results from growth curve modelling showed that over the follow-up period, novelty seeking and self-transcendence were both positively related to overall level of engagement in learning activities, although not to rate of change. Regarding specific activities, novelty seeking was related to higher levels of engagement in attending courses, taking on new education, and making occupational changes, while harm avoidance was negatively related to the likelihood of changing occupation. The results of this study underscore the importance of considering personality in relation to engagement in lifelong learning activities. Insights from this study can potentially increase the likelihood of finding methods to promote lifelong learning, which can be beneficial for educators, policymakers, and companies.

Background: Gastric cancer (GC) is clinically heterogenous according to location (cardia/non-cardia) and histopathology (diffuse/intestinal). We aimed to characterize the genetic risk architecture of GC according to its subtypes. Another aim was to examine whether cardia GC and oesophageal adenocarcinoma (OAC) and its precursor lesion Barrett's oesophagus (BO), which are all located at the gastro-oesophageal junction (GOJ), share polygenic risk architecture.

Methods: We did a meta-analysis of ten European genome-wide association studies (GWAS) of GC and its subtypes. All patients had a histopathologically confirmed diagnosis of gastric adenocarcinoma. For the identification of risk genes among GWAS loci we did a transcriptome-wide association study (TWAS) and expression quantitative trait locus (eQTL) study from gastric corpus and antrum mucosa. To test whether cardia GC and OAC/BO share genetic aetiology we also used a European GWAS sample with OAC/BO.

Findings: Our GWAS consisting of 5816 patients and 10,999 controls highlights the genetic heterogeneity of GC according to its subtypes. We newly identified two and replicated five GC risk loci, all of them with subtype-specific association. The gastric transcriptome data consisting of 361 corpus and 342 antrum mucosa samples revealed that an upregulated expression of MUC1, ANKRD50, PTGER4, and PSCA are plausible GC-pathomechanisms at four GWAS loci. At another risk locus, we found that the blood-group 0 exerts protective effects for non-cardia and diffuse GC, while blood-group A increases risk for both GC subtypes. Furthermore, our GWAS on cardia GC and OAC/BO (10,279 patients, 16,527 controls) showed that both cancer entities share genetic aetiology at the polygenic level and identified two new risk loci on the single-marker level.

Interpretation: Our findings show that the pathophysiology of GC is genetically heterogenous according to location and histopathology. Moreover, our findings point to common molecular mechanisms underlying cardia GC and OAC/BO. 

Objective: Suicidal behavior is heritable and is a major cause of death worldwide. Two large-scale genome-wide association studies (GWASs) recently discovered and crossvalidated genome-wide significant (GWS) loci for suicide attempt (SA). The present study leveraged the genetic cohorts from both studies to conduct the largest GWAS metaanalysis of SA to date. Multi-ancestry and admixture-specific meta-analyses were conducted within groups of significant African, East Asian, and European ancestry admixtures.

Methods: This study comprised 22 cohorts, including 43,871 SA cases and 915,025 ancestry-matched controls. Analytical methods across multi-ancestry and individual ancestry admixtures included inverse variance-weighted fixed-effects meta-analyses, followed by gene, gene-set, tissue-set, and drug-target enrichment, as well as summary-data-based Mendelian randomization with brain expression quantitative trait loci data, phenome-wide genetic correlation, and genetic causal proportion analyses.

Results: Multi-ancestry and European ancestry admixture GWAS meta-analyses identified 12 risk loci at p values <5×10-8. These loci were mostly intergenic and implicated DRD2, SLC6A9, FURIN, NLGN1, SOX5, PDE4B, and CACNG2. The multi-ancestry SNP-based heritability estimate of SA was 5.7% on the liability scale (SE=0.003, p=5.7×10-80). Significant brain tissue gene expression and drug set enrichment were observed. There was shared genetic variation of SA with attention deficit hyperactivity disorder, smoking, and risk tolerance after conditioning SA on both major depressive disorder and posttraumatic stress disorder. Genetic causal proportion analyses implicated shared genetic risk for specific health factors.

Conclusions: This multi-ancestry analysis of suicide attempt identified several loci contributing to risk and establishes significant shared genetic covariation with clinical phenotypes. These findings provide insight into genetic factors associated with suicide attempt across ancestry admixture populations, in veteran and civilian populations, and in attempt versus death.

Objectives: Prospective studies suggest that memory deficits are detectable decades before clinical symptoms of dementia emerge. However, individual differences in long-term memory trajectories prior to diagnosis need to be further elucidated. The aim of the current study was to investigate long-term dementia and mortality risk for individuals with different memory trajectory profiles in a well-characterized population-based sample.

Methods: 1062 adults (aged 45–80 years) who were non-demented at baseline were followed over 23–28 years. Dementia and mortality risk were studied for three previously classified episodic memory trajectory groups: maintained high performance (Maintainers; 26%), average decline (Averages; 64%), and accelerated decline (Decliners; 12%), using multistate modeling to characterize individuals’ transitions from an initial non-demented state, possibly to a state of dementia and/or death.

Results: The memory groups showed considerable intergroup variability in memory profiles, starting 10–15 years prior to dementia diagnosis, and prior to death. A strong relationship between memory trajectory group and dementia risk was found. Specifically, Decliners had more than a fourfold risk of developing dementia compared to Averages. In contrast, Maintainers had a 2.6 times decreased dementia risk compared to Averages, and in addition showed no detectable memory decline prior to dementia diagnosis. A similar pattern of association was found for the memory groups and mortality risk, although only among non-demented.

Conclusion: There was a strong relationship between accelerated memory decline and dementia, further supporting the prognostic value of memory decline. The intergroup differences, however, suggest that mechanisms involved in successful memory aging may delay symptom onset.