title: Physical activity and risk of venous thromboembolism. The Tromso study.
abstract: BACKGROUND
  Previous studies have shown differences in the impact of regular physical exercise on the risk of venous thromboembolism. The inconsistent findings may have depended on differences in study design and specific population cohorts (men only, women only and elderly). We conducted a prospective, population-based cohort to investigate the impact of regular physical exercise on the risk of venous thromboembolism.
  
  
  METHODS
  Risk factors, including self-reported moderate intensity physical exercise during leisure time, were recorded for 26,490 people aged 25-97 years old, who participated in a population health survey, the Tromsø study, in 1994-95. Incident venous thromboembolic events were registered during the follow-up until September 1, 2007.
  
  
  RESULTS
  There were 460 validated incident venous thromboembolic events (1.61 per 1000 person-years) during a median of 12.5 years of follow-up. Age, body mass index, the proportion of daily smokers, total cholesterol, and serum triglycerides decreased (P<0.001), whereas high density cholesterol increased (P<0.001) across categories of more physical exercise. Regular physical exercise of moderate to high intensity during leisure time did not significantly affect the risk of venous thromboembolism in the general population. However, compared to inactivity, high amounts of physical exercise (≥ 3 hours/week) tended to increase the risk of provoked venous thromboembolism (multivariable hazard ratio, 1.30; 95% confidence interval, 0.84-2.0), and total venous thromboembolism in the elderly (multivariable hazard ratio, 1.33; 95% confidence interval, 0.80-2.21) and in the obese (multivariable hazard ratio, 1.49; 95% confidence interval, 0.63-3.50). Contrariwise, compared to inactivity, moderate physical activity (1.0-2.9 hours/week) was associated with a border-line significant decreased risk of venous thromboembolism among subjects under 60 years old (multivariable hazard ratio, 0.72; 95% confidence interval, 0.48-1.08) and subjects with a body mass index of less than 25 kg/m(2) (multivariable hazard ratio, 0.59; 95% confidence interval, 0.35-1.01).
  
  
  CONCLUSIONS
  Our study showed that regular, moderate intensity physical exercise did not have a significant impact on the risk of venous thromboembolism in a general population. Future studies are required to assess the impact of regular physical exercise on venous thromboembolism risk in different population subgroups.
authors.affiliation: Hematological Research Group (HERG), Department of Medicine, Institute of Clinical Medicine, University of Tromsø, N-9037 Tromsø, Norway. knut.borch@uit.no
authors.forename: Knut H
authors.initials: KH
authors.lastname: Borch
authors.forename: Ida
authors.initials: I
authors.lastname: Hansen-Krone
authors.forename: Sigrid K
authors.initials: SK
authors.lastname: Braekkan
authors.forename: Ellisiv B
authors.initials: EB
authors.lastname: Mathiesen
authors.forename: Inger
authors.initials: I
authors.lastname: Njolstad
authors.forename: Tom
authors.initials: T
authors.lastname: Wilsgaard
authors.forename: John-Bjarne
authors.initials: JB
authors.lastname: Hansen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D002784:Cholesterol / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005260:Female; D006306:Health Surveys / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D011446:Prospective Studies; D012042:Registries / Q000706:statistics & numerical data; D018570:Risk Assessment; D012307:Risk Factors; D012907:Smoking / Q000503:physiopathology; D014280:Triglycerides / Q000097:blood; D054556:Venous Thromboembolism / Q000097:blood / Q000453:epidemiology* / Q000503:physiopathology
chemical_list: D014280:Triglycerides; D002784:Cholesterol
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