title: Physical activity and the risk of incident atrial fibrillation in women.
abstract: BACKGROUND
  Physical activity (PA) is well known to reduce the risk of cardiovascular disease. We hypothesized that regular PA, possibly acting through reductions in blood pressure and body mass index (BMI), would reduce the risk of incident atrial fibrillation (AF) in women.
  
  
  RESULTS
  We prospectively followed 34 759 women who reported their leisure-time PA levels for the occurrence of AF. We estimated energy expenditure in metabolic equivalent (MET)-h/wk and validated self-reported AF with medical records. The mean (SD) age of the 34 759 participants was 54.6 (7.0) years, the mean BMI was 26.0 (5.0) kg/m(2), 26.5% had hypertension, and the median (IQR) PA was 8.4 (2.8, 20.4) MET-h/wk. After a median of 14.4 years of observation, 968 women had development of AF. In age-, cholesterol-, smoking-, alcohol-, diabetes-, and race-adjusted models, increasing quintiles of PA were associated with reduced risks of AF (hazard ratio for extreme quintiles, 0.82; 0.66 to 1.01; P trend=0.007 over quintiles). Although this association was not substantially different after adjusting for hypertension (0.87; 0.70 to 1.07; P trend 0.02), it was attenuated after adjustment for BMI (0.99; 0.80 to 1.23; P trend=0.22). Women who achieved the federal government's recommendation of 7.5 MET-h/wk of PA were at reduced risk of AF compared with those who did not (0.86; 0.75 to 0.98; P=0.03). This association was also attenuated by BMI (0.96; 0.84 to 1.10; P=0.57).
  
  
  CONCLUSIONS
  In middle-aged women, physical activity was associated with a modestly reduced risk of AF. However, this relationship was no longer significant after controlling for body mass index.
authors.affiliation: Department of Medicine, Cardiovascular Division, Brigham and Women’s Hospital, 900 Commonwealth Ave E., Boston, MA 02215, USA. beverett@partners.org
authors.forename: Brendan M
authors.initials: BM
authors.lastname: Everett
authors.forename: David
authors.initials: D
authors.lastname: Conen
authors.forename: Julie E
authors.initials: JE
authors.lastname: Buring
authors.forename: M V
authors.initials: MV
authors.lastname: Moorthy
authors.forename: I-Min
authors.initials: IM
authors.lastname: Lee
authors.forename: Christine M
authors.initials: CM
authors.lastname: Albert
mesh_terms: D001281:Atrial Fibrillation / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D001794:Blood Pressure / Q000502:physiology; D015992:Body Mass Index; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D011446:Prospective Studies; D012307:Risk Factors; D057566:Self Report