Assessment of vitamin D levels in type 1 and type 2 diabetes patients: Results from metaanalysis

Accumulating evidence indicates that vitamin D deficiency is prevalent in patients with type 1 (T1D) and type 2 diabetes (T2D). The present study aims to assess 25-hydroxyvitamin D [25(OH)D] levels in T1D and T2D patients compared with controls through a metaanalysis.We searched databases for articles published until January 2015. A total of 12 studies covering 2003 patients and 1882 controls and 11 studies covering 2236 patients and 2438 controls were included to metaanalyze 25(OH)D levels in patients with T1D and T2D, respectively. Pooled data showed that T1D patients had lower levels of 25(OH)D than controls (summary standardized mean difference (SMD) -0.70, 95% confidence interval (CI) -1.02 to -0.37). Further age-subgroup analysis found that 25(OH)D levels in T1D patients was also significantly lower than controls in subgroup aged ≤ 14 years (summary SMD -1.04, 95% CI -1.55 to -0.53), while the association is not statistically significant in the subgroup aged > 14 years. Similarly, T2D patients had lower 25(OH)D levels compared with controls (summary SMD -0.58, 95%CI -1.16 to -0.00).Available data indicated that both T1D and T2D patients had lower levels of 25(OH)D than controls overall. The mechanistic underpinnings of this association warrant further elucidation.