Relationships Between Vitamin D status and Age-related Macular Degeneration (AMD) in the Carotenoids and Age-Related Eye Disease Study, an Ancillary Study of the Women’s Health Initiative Observational Study (WHIOS)

Abstract

Purpose: : To investigate the relationship between vitamin D status and the prevalence of intermediate AMD among participants of the Carotenoids in Age-Related Eye Disease Study (CAREDS), an ancillary study of the WHIOS.

Methods: : CAREDS (2001-04) enrolled 2,005 women (50-79 years) from 3 WHIOS sites in Iowa, Oregon, and Wisconsin. At that time, AMD was assessed from stereoscopic fundus photographs. At WHIOS baseline (1994-98), serum 25-hydroxyvitamin D (25(OH)D) levels were assessed in 1,475 participants. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for prevalent intermediate AMD (n=241) by quintile of serum 25(OH)D among 1,313 women with gradable photographs and complete risk factor data. ORs were adjusted for age, month of blood draw, packyears of smoking, prevalent diabetes, family history of AMD, iris pigment color, history of cardiovascular disease, and use of hormone replacement therapy.

Results: : No significant relationship was observed between AMD and serum 25(OH)D (OR for AMD among women in high vs. low quintiles of serum 25(OH)D=0.82, 95% CI=0.51, 1.33; p_trend=0.49). However, there was a significant age interaction (p<0.0001). Associations with AMD were direct in women ≥75 years. In women < 75 years (n=968), a 43% decreased odds of AMD in high vs. low quintiles of serum 25(OH)D was observed (OR=0.57, 95% CI=0.33, 0.99; p_trend=0.02). Additionally, among women < 75 years, protective associations were consistent for food and supplement sources of vitamin D. Conversely, AMD was not related to estimated hours of ambient sun exposure (OR for tertile three vs.one for ambient sun exposure=0.94, 95% CI=0.57, 1.55; p_trend=0.32).

Conclusions: : High serum 25(OH)D status may be protective against intermediate AMD in women < 75 years. The inverse direction of associations were consistent across oral sources of vitamin D. Lack of an association between ambient sun exposure and intermediate AMD may reflect measurement error, variable ability to synthesize vitamin D in the skin, or suggest that sun exposure is not a strong determinant of serum vitamin D among women at such northern climates.

Keywords: age-related macular degeneration • nutritional factors • clinical (human) or epidemiologic studies: prevalence/incidence