Abstract 4023: Do Known Risk Factors Explain the Inverse Relation Between Physical Activity and Cardiovascular Disease Risk?
Background Physical activity clearly decreases the risk of cardiovascular disease (CVD), but the precise mechanisms through which it exerts its protective effects are unclear.
Methods We examined the extent to which novel and traditional CVD risk factors mediated the association between physical activity and risk of incident CVD during a 10-year follow-up period. Participants were 27158 apparently healthy women age ≥45 years enrolled in the Women’s Health Study with baseline measurements of: creatinine, homocysteine, hemoglobin A1c, traditional lipids (total, LDL, and HDL cholesterol), novel lipids (lipoprotein (a), apolipoprotein B100 and A1), and inflammatory biomarkers (high-sensitivity C-reactive protein, fibrinogen and soluble intracellular adhesion molecule). Additionally, participants reported information on blood pressure/hypertension, smoking, diet, menopause, and family history. Physical activity was assessed based on reported leisure-time activities and stair climbing.
Results In age-adjusted analysis, there was a strong inverse association between physical activity and risk of CVD. The relative risks (RRs) associated with physical activity levels of <200, 200–599, 600–1499, and ≥1500 kcal/week were 1.00, 0.69, 0.65, and 0.57, respectively; Ptrend<0.001. After additional adjustment for potential confounders (smoking, alcohol, fruits and vegetables, menopause, hormone use, and parental history), corresponding RR’s were 1.00, 0.77, 0.72, and 0.66; Ptrend<0.001. When we added all measured variables (creatinine, homocysteine, hemoglobin A1c, traditional and novel lipids, inflammatory biomarkers) and blood pressure/ hypertension, the inverse association was attenuated and no longer significant; corresponding RR’s were 1.00, 0.89, 0.91, 0.84, respectively; Ptrend<0.19. Of these variables examined separately, inflammatory biomarkers were responsible for the largest attenuation in results. The addition of body mass index or education to models did not alter the findings.
Conclusions The strong inverse association between physical activity and incident CVD appears to be mediated in substantial part by known risk factors, in particular those related to inflammation.