Low vitamin D levels are associated with high viral loads in patients with chronic hepatitis B: a systematic review and meta-analysis

BACKGROUND: Previous studies have investigated the vitamin D status in patients with chronic hepatitis B virus (HBV) infection and its relationship with HBV replication, the results however were inconsistent. The present meta-analysis was carried out to compare the vitamin D levels between patients with chronic hepatitis B (CHB) and healthy controls, and to determine whether vitamin D levels were correlated with HBV viral loads significantly. METHODS: A systematic search was conducted via PubMed, Web of Science, EMBASE and the Cochrane Library to identify eligible studies until September 28, 2017. We calculated pooled mean difference (MD) and 95% confidence intervals (CI) to quantitatively estimate the difference of vitamin D levels between CHB patients and controls. In addition, correlation between serum vitamin D levels and HBV viral loads was defined by summary correlation coefficient (r value) and the corresponding 95% CI. RESULTS: A total of 7 studies involving 814 CHB patients and 696 healthy controls were included. A significantly decreased vitamin D levels was found in CHB patients compared with healthy controls: pooled MD (95% CI) was − 2.03 ng/mL (− 2.60, − 1.46). Latitude-stratified subgroup analysis indicated this difference was more obvious in low latitude areas, with a bigger pooled MD (95% CI) of − 2.72 ng/mL (− 4.57, − 0.87). In addition, we observed an inverse correlation between serum vitamin D levels and HBV viral loads: pooled r (95% CI) was − 0.41(− 0.54, − 0.27). CONCLUSIONS: Our results showed that vitamin D levels were lower in CHB patients than that of healthy controls and inversely correlated with HBV viral loads, although future comprehensive studies are needed to clarify the underlying mechanisms. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12876-019-1004-2) contains supplementary material, which is available to authorized users.