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Risk factors assessed in adolescence and the later risk of stroke in men: a 33-year follow-up study
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Sports Medicine.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Sports Medicine.
Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.ORCID iD: 0000-0003-3298-1555
Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Geriatric Medicine.
2015 (English)In: Cerebrovascular Diseases, ISSN 1015-9770, E-ISSN 1421-9786, Vol. 39, no 1, 63-71 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Stroke is a common cause of death, and a leading contributor to long-term disability. The cost associated with the disease is great. Several modifiable risk factors for stroke have been found in older cohorts; however, no study to date has investigated the effects of these risk factors from late adolescence.

METHODS: The study cohort comprised 811,579 Swedish men (mean age, 18 years) that participated in the mandatory military conscription service in Sweden between 1969 and 1986. Some risk factors for stroke, such as body mass index, systolic and diastolic blood pressure, and cognitive function, were assessed at conscription. Aerobic fitness was also assessed at conscription, using a braked ergometer cycle test. Other risk factors for stroke, including stroke in subjects' parents, and socioeconomic factors including highest achieved level of education and annual income 15 years after conscription, were collected through national register linkage using the personal identification number. Stroke diagnosis among the study participants was tracked in the National Hospital Discharge Patient Register.

RESULTS: During a median follow-up period of 33 years 6,180 ischemic strokes and 2,104 hemorrhagic strokes were diagnosed in the cohort at a mean age of 47.9 years. Strong independent risk factors (all p <1.0 × 10-(6)) for ischemic stroke included low aerobic fitness (hazard ratio [HR], 0.84 per standard deviation [SD] increase), high BMI (HR, 1.15 per SD increase), diabetes (HR, 2.85), alcohol intoxication (HR, 1.93), low annual income (HR, 0.85 per SD decrease), and stroke in the mother (HR, 1.31). Similar risk factors were found for hemorrhagic stroke including low aerobic fitness (HR, 0.82 per SD increase), high BMI (HR, 1.18 per SD increase) alcohol intoxication (HR, 2.92), diabetes (HR, 2.06), and low annual income (HR, 0.75). The population attributable risks associated with all evaluated risk factors were 69% for ischemic stroke and 88% for hemorrhagic stroke (p < 0.001 for both).

CONCLUSIONS: In the present study we have shown that several known risk factors for stroke are present already in late adolescence, and that they are independent of each other. The strongest risk factors were low physical fitness, high BMI, diabetes, low annual income and a maternal history of stroke. Several of the aforementioned risk factors are potentially modifiable.

Place, publisher, year, edition, pages
2015. Vol. 39, no 1, 63-71 p.
National Category
Cardiac and Cardiovascular Systems Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
URN: urn:nbn:se:umu:diva-99250DOI: 10.1159/000369960ISI: 000348213700008PubMedID: 25547343Scopus ID: 2-s2.0-84920838888OAI: oai:DiVA.org:umu-99250DiVA: diva2:786199
Available from: 2015-02-05 Created: 2015-02-05 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Cardiovascular disease and all-cause mortality: influence of fitness, fatness and genetic factors
Open this publication in new window or tab >>Cardiovascular disease and all-cause mortality: influence of fitness, fatness and genetic factors
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background

Low aerobic fitness and obesity are associated with atherosclerosis, and thereforegreatly increase the risk of cardiovascular disease (CVD) and early death. It has long been known that atherosclerosis my begin early in life. Despite this fact, it remains unknown how obesity and aerobic fitness early in life influence the risks of atherosclerosis, CVD and death. Furthermore, it is unknown whether high aerobic fitness can compensate for the risks associated with obesity, and how genetic confounding affects the relationshipsof aerobic fitness with CVD and all-cause mortality. Thus, the main aims of this thesis were to investigate the associations of aerobic fitness in late adolescence with myocardial infarction (Study I), stroke (Study II) and all-cause mortality (Study III), and how genetic confounding influences the relationshipsof aerobic fitness with CVD, diabetes and death (Study IV).

Methods

The study population comprised up to1.3 million men who participated in mandatory Swedish military conscription. During conscription, all conscripts underwent highly standardized tests to assess aerobic fitness, body mass index, blood pressure and cognitive function. A physician also examined all conscripts. Data on subjects’ diagnoses, death and socioeconomic status during follow-up were retrieved using record linkage. Subjects were subsequently followed until the study endpoint, date of death or date of any outcome of interest. Associations between baseline variables and the risks of adverse outcomes were assessed using Cox’s proportional hazard models. Genetic confounding of the relationships between aerobic fitness and diabetes, CVD and death was assessed using a twin population and a paired logistic regression model.

Results

In Study I, low aerobic fitness at conscription was associated with an increased risk of myocardial infarction (MI) during follow-up (hazard ratio [HR] 0.82 per standard deviation increase). Similarly, in Study II, high aerobic fitness reduced the risk of stroke (HR 0.84 for ischemic stroke, HR 0.82 for hemorrhagic stroke; P < 0.001 for all), and obesity was associated with an increased risk of stroke (HR 1.15 for ischemic stroke, HR 1.18 for hemorrhagic stroke; P < 0.001 for all). In Study III, high aerobic fitness was also associated with reduced all-cause mortality later in life (HR 0.49, P < 0.001). High aerobic fitness exerted the strongest protection against death from substance and alcohol abuse, suicide and trauma (HRs 0.20, 0.41 and 0.52, respectively; P < 0.001 for all). Obese individuals with aerobic fitness were at higher risk of MI and all-cause mortality than were normal-weight individuals with low fitness (Studies I and III). In Study IV, fit twins had no reduced risk of CVD or death during follow-up compared with their unfit twin siblings (odds ratio 1.11, 95% confidence interval 0.88–1.40), regardless of how large the difference in fitness was. However, the fitter twins were protected against diabetes during follow-up.

Conclusions

Already early in life, aerobic fitness is a strong predictor of CVD and all-cause mortality later in life. In contrast to the “fat but fit” hypothesis, it seems that high aerobic fitness cannot fully compensate for the risks associated with obesity. The associationsof aerobic fitness with CVD and all-cause mortality appear to be mediated by genetic factors. Together, these findings have implications for the view of aerobic fitness as a causal risk factor for CVD and early death.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2017. 83 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1865
Keyword
all-cause mortality, aerobic fitness, obesity, cardiovascular disease, stroke, myocardial infarction
National Category
Public Health, Global Health, Social Medicine and Epidemiology Cardiac and Cardiovascular Systems
Research subject
Epidemiology; Population studies; Cardiology
Identifiers
urn:nbn:se:umu:diva-130312 (URN)978-91-7601-611-4 (ISBN)
Public defence
2017-02-10, Aulan, Vårdvetarhuset, Umeå universitet, Umeå, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2017-01-20 Created: 2017-01-17 Last updated: 2017-01-27Bibliographically approved

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