HEALTH NEWS

Study Title:

Vitamin D and Macular Degeneration

Study Abstract

Objective The relationship between serum 25-hydroxyvitamin D (25[OH]D) concentrations (nmol/L) and the prevalence of early age-related macular degeneration (AMD) was investigated in participants of the Carotenoids in Age-Related Eye Disease Study.

Methods Stereoscopic fundus photographs, taken from 2001 to 2004, assessed AMD status. Baseline (1994-1998) serum samples were available for 25(OH)D assays in 1313 women with complete ocular and risk factor data. Odds ratios (ORs) and 95% confidence intervals (CIs) for early AMD (n = 241) of 1287 without advanced disease were estimated with logistic regression and adjusted for age, smoking, iris pigmentation, family history of AMD, cardiovascular disease, diabetes, and hormone therapy use.

Results In multivariate models, no significant relationship was observed between early AMD and 25(OH)D (OR for quintile 5 vs 1, 0.79; 95% CI, 0.50-1.24; P for trend = .47). A significant age interaction (P = .002) suggested selective mortality bias in women aged 75 years and older: serum 25(OH)D was associated with decreased odds of early AMD in women younger than 75 years (n = 968) and increased odds in women aged 75 years or older (n = 319) (OR for quintile 5 vs 1, 0.52; 95% CI, 0.29-0.91; P for trend = .02 and OR, 1.76; 95% CI, 0.77-4.13; P for trend = .05, respectively). Further adjustment for body mass index and recreational physical activity, predictors of 25(OH)D, attenuated the observed association in women younger than 75 years. Additionally, among women younger than 75 years, intake of vitamin D from foods and supplements was related to decreased odds of early AMD in multivariate models; no relationship was observed with self-reported time spent in direct sunlight.

Conclusions High serum 25(OH)D concentrations may protect against early AMD in women younger than 75 years.

From press release:

Higher levels of circulating vitamin D appear to reduce the risk for early onset of age-related macular degeneration in women ages 50 to 74, an ancillary study of the Women's Health Initiative showed.

Among postmenopausal women younger than 75, those who had the highest concentrations of 25 (OH)D (at least 75 nmol/L) were significantly less likely to develop the eye condition than those with the lowest (38 nmol/L or lower), according to Amy Millen, PhD, of the University at Buffalo in New York, and colleagues.

The odds ratio was 0.52 (95% CI 0.29 to 0.91) after adjustment for age, smoking, iris pigmentation, family history of age-related macular degeneration, cardiovascular disease, diabetes, and hormone therapy use, the researchers reported in the April issue of Archives of Ophthalmology.

Further adjustment for body mass index and physical activity, however, rendered the association nonsignificant, likely because of the strong correlation between those two factors and vitamin D status, Millen and her colleagues wrote.

"More studies are needed to verify this association prospectively as well as to better understand the potential interaction between vitamin D status and genetic and lifestyle factors with respect to risk of early age-related macular degeneration," they wrote.

The findings confirm the strong inverse relationship between serum 25-hydroxyvitamin D concentrations and early age-related macular degeneration found using data from the National Health and Nutrition Examination Survey (NHANES).

Millen and her colleagues looked at data from the Carotenoids in Age-Related Eye Disease Study (CAREDS), which was conducted under the umbrella of the Women's Health Initiative Observational Study. In CAREDS, age-related macular degeneration status was assessed an average of six years after serum samples were analyzed for 25(OH)D status.

The current analysis included 1,313 women ages 50 to 79. Overall, 241 women developed early age-related macular degeneration and 26 developed advanced disease.

The median serum 25 (OH)D level was 30 nmol/L in the lowest quintile and 85 nmol/L in the highest.

In a multivariate analysis of women of all ages, there was no significant relationship between early age-related macular degeneration and 25(OH)D concentration (OR for the highest versus the lowest quintile 0.79, 95% CI 0.50 to 1.24).

There was, however, a significant interaction with age (P=0.002), which suggested a selective mortality bias in women 75 and older, according to the researchers.

Although there was a decrease in the odds of early age-related macular degeneration with increasing 25(OH)D levels in women younger than 75, there was a nonsignificant trend in the opposite direction for older women (OR 1.76, 95% CI 0.77 to 4.13).

Further adjustment for BMI and recreational physical activity, however, weakened both associations.

Also in women younger than 75, increased intake of vitamin D from foods and supplements combined was associated with lower odds of early age-related macular degeneration -- consuming at least 18µg/day was associated with 59% lower odds of developing the condition (OR 0.41, 95% CI 0.20 to 0.78).

The authors noted that that level of intake equals 720 IU/day, which exceeds to Institute of Medicine's recommendation for 600 IU/day.

There was not association between time spent in direct sunlight and the likelihood of developing macular degeneration.

Millen and her colleagues acknowledged some limitations of the study, including the inability to establish causality using an observational study, the limited generalizability beyond postmenopausal white women, possible selection bias, and the lack of information on genetic risk factors for age-related macular degeneration.

Study Information

Amy E. Millen, PhD; Rick Voland, PhD; Sherie A. Sondel, MS; Niyati Parekh, PhD; Ronald L. Horst, PhD; Robert B. Wallace, MD; Gregory S. Hageman, PhD; Rick Chappell, PhD; Barbara A. Blodi, MD; Michael L. Klein, MD; Karen M. Gehrs, MD; Gloria E. Sarto.
Vitamin D Status and Early Age-Related Macular Degeneration in Postmenopausal Women
Arch Ophthalmol.
2011 April
CAREDS Study Group