Serum vitamin D levels and erectile dysfunction: A systematic review and meta-analysis.

Suboptimal levels of serum vitamin D levels have been implied to be associated with cardiovascular diseases and endothelial dysfunction, conditions closely associated with erectile dysfunction (ED). The present systematic review and meta-analysis was performed to evaluate the vitamin D levels in subjects with ED compared to controls and the 5-item version of the international index of erectile function (IIEF-5) score in subjects with vitamin D deficiency compared to those without vitamin D deficiency in order to elucidate the role of vitamin D in the pathogenesis of ED. Studies evaluating the possible association between vitamin D levels and ED were initially screened and thus included following electronic literature search of database Cochrane Library, PUBMED, EMBASE and MEDLINE. Essential article information including outcome measures was extracted from the qualified studies by two independent authors, and STATA 12.0 software was used conducted the meta-analysis. Subgroup analyses were conducted by vitamin D detection methods and sample size. The standard mean difference (SMD) as well as the 95% confidence intervals (95% CIs) was applied to estimate the outcome measures. A total of seven articles were included in our meta-analysis with a total of 4,132 subjects. Pooled estimate was in favour of increased vitamin D levels in subjects without ED with a SMD of 3.027 ng/ml, 95%CI 2.290-3.314, p = 0.000. However, subgroup analysis showed an opposite trend, after one study with a sample size over 1,000 that could possibly influence the weight balance was excluded, with a SMD of 0.267, 95%CI -0.052 to 0.585, p = 0.101. We also identified about 0.320 higher in IIEF-5 score (95%CI = 0.146-0.494, p = 0.000) in subjects without vitamin D deficiency versus with vitamin D deficiency. Nevertheless, subgroup analysis based on vitamin D detection methods obtained differential results (radioimmunoassay subgroup, SMD(95%CI) = 0.573 (0.275-0.870), p = 0.000; immunoassay subgroup, SMD(95%CI) = 0.189 (-0.025 to 0.404), p = 0.084). In conclusion, results from the present meta-analysis did not provide a strong relationship between vitamin D and the risk of ED. However, the results should be interpreted with caution and more high quality studies are warranted.