Abstract
Purpose: :
We investigated relationships between physical activity and the prevalence of intermediate AMD assessed an average of six years later.
Methods: :
Post-menopausal women (ages 50-79 years) in this sample provided information about diet, lifestyle and risk factors at the time of entry into the WHI Observational Studies (1994-1997) in Iowa, Wisconsin and Oregon. Intermediate AMD was assessed from stereoscopic fundus photographs taken in CAREDS (2001-2004) (N=1,787.) For these analyses women under age 75 were selected (N=1,313) based on evidence for selective mortality bias in older women. At WHIOS baseline (1994-1998) women were asked about participation in total recreational physical activity (MET-hours/week) which includes walking, strenuous, moderate, and intensive activities.
Results: :
Physical activity was strongly associated with a reduction in risk of AMD: The odds ratio [OR] (95% Confidence Interval [CI]) for AMD among women in the top quintile (> 25 MET-hrs/wk) compared with the bottom quintile (< 2.2 MET-hrs/week) of total recreational physical activity was 0.49 (0.28-0.84) P-trend = 0.005, after adjusting for age at eye photography, smoking packyears, history of diabetes, family history of AMD, iris pigment color, history of cardiovascular disease, hormone use status and score on 2005 Healthy Eating Index. This association may reflect, in part, lower body mass index (BMI) and better vitamin D status in woman who were physically active: In a sub sample of these women who had vitamin D values measured from serum (n=968) the OR (95% CI) for AMD was 0.52 (0.27-0.97) in high vs. low quintiles of MET-hrs/week; P-trend= 0.04 after adjusting for previously stated risk factors and was attenuated to 0.59 (0.30-1.12) P-trend = 0.10, after further adjustment for BMI and serum vitamin D.
Conclusions: :
Greater physical activity was associated with reduced risk of intermediate AMD, a condition not severe enough to limit activity. This risk reduction may be partly mediated by lower BMI and better vitamin D status among physically active women.
Keywords: age-related macular degeneration • clinical (human) or epidemiologic studies: risk factor assessment • nutritional factors