The Association Between Serum Vitamin D Levels and Age-Related Macular Degeneration: A Systematic Meta-Analytic Review.
OBJECTIVE
We conducted a meta-analysis of individual studies reporting an association between serum vitamin D levels and AMD.


METHODS
Relevant studies evaluating the association between serum vitamin D levels and AMD risk were identified by systematically searching four electronic literature databases (Ovid Medline, PubMed, EMBASE, and ISI Web of Science) censored by June 2015. Due to the heterogeneity of studies in categorizing serum vitamin D levels, all individual odds ratios (ORs) were recalculated and transferred for an increase of serum vitamin D levels by 10 ng/ml. Summary ORs and 95% confidence intervals (CIs) of AMD risk per 10-unit increase of serum vitamin D were obtained using standard meta-analysis. Publication bias was evaluated using funnel plots and Kendall's rank correlation tests.


RESULTS
Ten individual studies were included and pooled in this meta-analysis. Meta-analysis of studies on AMD risk led to a pooled OR (95% CI) of 0.91 (0.69-1.22) for an increase of 25-hydroxy vitamin D by 10 ng/mL (P = 0.12). No indication for publication bias was found, but substantial heterogeneity was obtained (I2 = 79.7%, P < 0.01). Estimates from subgroup analyses also did not show statistically significant associations of serum vitamin D levels with different stages (early AMD, late AMD, and advanced AMD) and subtypes of AMD (neovascular AMD and nonneovascular AMD; P > 0.05).


CONCLUSIONS
There is no evidence to indicate an inverse association between serum vitamin D levels and any stages and subtypes of AMD risk, but opposite results from the United States and Korea resulted in this nonsignificance. Potential difference across various study designs might exist, based on few studies reporting in heterogeneous manners so far. More studies are needed to further confirm the causality of vitamin D and AMD, especially longitudinal studies.
Eye Center Second Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China 2Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou, Zhejiang, China.
Wei
W
Wu
Eye Center Second Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China 2Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou, Zhejiang, China.
Yan
Y
Weng
Institute of Occupational Diseases, Zhejiang Academy of Medical Sciences, Hangzhou, Zhejiang, China.
Xinnian
X
Guo
Institute of Occupational Diseases, Zhejiang Academy of Medical Sciences, Hangzhou, Zhejiang, China.
Lingfang
L
Feng
Institute of Occupational Diseases, Zhejiang Academy of Medical Sciences, Hangzhou, Zhejiang, China.
Hailing
H
Xia
Institute of Occupational Diseases, Zhejiang Academy of Medical Sciences, Hangzhou, Zhejiang, China.
Zhaoqiang
Z
Jiang
Institute of Occupational Diseases, Zhejiang Academy of Medical Sciences, Hangzhou, Zhejiang, China.
Jianlin
J
Lou
D006801:Humans; D008268:Macular Degeneration / Q000097:blood / Q000209:etiology*; D012307:Risk Factors; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000150:complications
D014807:Vitamin D