Vitamin D Deficiency and Increased Risk of Bladder Carcinoma: A Meta-Analysis

Vitamin D status in relation to bladder carcinoma risk was still inconsistent. This study was carried out to evaluate the relationship between vitamin D status and bladder carcinoma risk through a meta-analysis approach.

Pubmed, Web of Science, CNKI, and Embase were searched systemically to find eligible studies from the earliest available date to April 16, 2015. The search terms "vitamin D", "25-hydroxyvitamin D", "bladder cancer" or "bladder carcinoma" were used to retrieve relevant studies. The exposure of interest was intake of vitamin D or serum vitamin D levels, and the outcome of interest was bladder carcinoma incidence or mortality. The pooled risk ratio (RR) values and their 95%CIs were calculated through meta-analysis.

Seven studies with a total of 62,141 participants met the inclusion criteria and were finally included into the meta-analysis. There was no heterogeneity among those included studies (I2 = 0%, P = 0.53). The pooled RR of bladder carcinoma for the lowest category versus the highest category of vitamin D was 1.34 (95% CI 1.17-1.53, P < 0.0001). Sensitivity analysis by omitting one study by turns showed all the pooled RRs were statistically significant. Meta-analysis of 5 studies reporting outcomes of serum vitamin D levels also showed that the low serum vitamin D level was associated with increased risk of bladder carcinoma (RR = 1.32, 95%CI 1.15-1.52, P = 0.0001). No obvious risk of publication bias was observed.

Vitamin D deficiency is associated with increased risk of bladder carcinoma in present study.