Purpose: The aim of this study was to quantify the relationship between categories of body mass index (BMI) and age-related macular degeneration (AMD) risk in different stages.
Methods: MEDLINE, EMBASE, and ISI Web of Science were searched for all eligible studies on the relationship between BMI and incident early or late AMD. The analyses were based on data extracted from study reports. The pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated to evaluate the strength of this association, and dose-response relationship was assessed by restricted cubic spline.
Results: Seven prospective cohort studies with 1613 cases identified among 31,151 subjects were included. For overweight, the relationship remained insignificant for its association with both early AMD (RR = 0.92, 95% CI: 0.68-1.15; P = 0.54) and late AMD (RR = 1.09, 95% CI: 0.93-1.25; P = 0.18). A marked 32% increase in the risk of developing late AMD was noted among obese individuals (RR = 1.32, 95% CI: 1.11-1.53, P < 0.01), while obesity showed no significant association with early AMD (RR = 0.91, 95% CI: 0.74-1.08; P = 0.67). Furthermore, elevated BMI showed a linear dose-response relation with AMD risk (Pnonlinearity = 0.17), and the AMD risk increased by 2% (RR = 1.02, 95% CI: 1.01-1.04) for each 1 kg/m2 increase in BMI within the overweight and obese BMI ranges.
Conclusions: Excess body weight was weakly associated with increase in the risk of AMD in a dose-dependent fashion, especially for its late stage, indicating that keeping normal body weight and avoiding further weight gain may confer potential protection against this disease.