The impact of vitamin D status on retinopathy and nephropathy among patients with type 2 diabetes mellitus: a meta-analysis

Abstract

Abstract Aims/hypothesis: Vitamin D is a fat-soluble hormone that plays an essential role in many physiological functions in the body. Various studies and reviews have documented the association between a low level of vitamin D and diabetic microvascular complications. Therefore, we conducted a meta-analysis to assess the association between serum 25-hydroxyvitamin D [25(OH)D] and diabetic nephropathy (DN) as well as diabetic retinopathy (DR). Methods: We conducted a systemic literature search of PubMed, Scopus, Google Scholar, and Trip Database. Twelve observational studies were included to assess the association between vitamin D deficiency (VDD) and DR, as well as the effect of both vitamin D deficiency and insufficiency in terms of increasing the risk of DN among T2DM patients. The odds ratio was used to measure the relationship between vitamin D status and the risk of DN and DR. We compared the number of events (DN or DR at any stage) in the control group with VDD or vitamin D insufficiency groups. Results: VDD (25(OH)D level < 20 ng/mL) significantly increased the risk of DR and DN among patients with T2DM with (OR=1.51, 95% CI: 1.11,2.07, I2=77%,) and (OR=1.68, 95% CI: 1.39,2.03, I2=76%), respectively. Moreover, vitamin D insufficiency (25(OH)D level < 30 ng/mL) was also significantly associated with the development of DN in T2DM patients with (OR=2.03, 95% CI: 1.53,2.71, I2=39%,). Conclusions/interpretation: T2DM Patients with low serum [25(OH)D] levels are at a higher risk of developing retinopathy and/or nephropathy compared to diabetic patients with normal vitamin D levels.