Serum folate, vitamin B12 levels and diabetic peripheral neuropathy in type 2 diabetes: A meta-analysis.

The association between serum folate and vitamin B12 levels and the risk of diabetic peripheral neuropathy (DPN) remains unclear. This meta-analysis included 16 studies of serum folate levels (1190 cases and 1501 controls) and 18 studies of serum vitamin B12 levels (1239 cases and 1562 controls) in patients with type 2 diabetes mellitus (T2DM). Reduced serum levels of folate and vitamin B12 were found in patients with T2DM and DPN compared with patients with T2DM but without DPN; weighted mean difference (WMD) = -1.64 (95% confidence interval [CI] = -2.46, -0.81) and WMD = -70.86 (95% CI = -101.55, -40.17), respectively. A subgroup analysis confirmed these associations in the Chinese population, but not in the Caucasian and mixed populations. In conclusion, these findings support the need for further controlled studies in defined patient populations and the importance of monitoring serum folate and vitamin B12 levels in patients with T2DM.