Prospective study of incident age-related macular degeneration in relation to vigorous physical activity during a 7-year follow-up.

PURPOSE: To test whether the risk of age-related macular degeneration (AMD) decreases with vigorous physical activity.
METHODS: This was a prospective study of self-reported clinically diagnosed macular degeneration in male (n = 29,532) and female (n = 12,176) runners followed prospectively for 7.7 years. Survival analyses of incident AMD versus average running distance (kilometers per day), cardiorespiratory fitness (10-km footrace performance), body mass index (BMI), cigarette use, and diet at baseline.
RESULTS: The 110 men and 42 women reporting incident AMD were older than those unaffected (mean +/- SE: 54.81 +/- 0.97 vs. 44.86 +/- 0.06 years), and the men were significantly more likely to have once smoked cigarettes (50.6 vs. 41.2%, P = 0.04 when adjusted for age). Age- and sex-adjusted AMD risk was greater in the men and women who consumed more meat (3.17 +/- 0.20 vs. 2.55 +/- 0.02 servings/wk) and less fruit (9.41 +/- 0.70 vs. 10.92 +/- 0.05 pieces/wk). The men and women reporting incident AMD ran for exercise significantly less than those who remained unaffected, when adjustment was made for age and sex (4.57 +/- 0.30 vs. 5.34 +/- 0.02 km/d, P < or = 0.01). When adjusted for age, sex, diet, and smoking history, the relative risk for AMD decreased 10% per km/d increment in running distance. Moreover, compared with the men and women who averaged less than 2 km/d, those averaging 2 to 4 km/d had 19% lower adjusted risk, and those averaging > or = 4 km/d had 42% to 54% lower adjusted AMD risk.
CONCLUSIONS: Higher doses of vigorous exercise (running) are associated with lower incident AMD risk independent of weight, cardiorespiratory fitness, and cigarette use. Limitations of the analyses include the select nature of the sample and reliance on self-report of both running history and clinically diagnosed AMD.