Number of parity and the risk of gallbladder cancer: a systematic review and dose-response meta-analysis of observational studies.Arch Gynecol Obstet 2016; 293(5):1087-96AG
Current epidemiological evidence suggests an association between parity and risk of gallbladder cancer (GBC), but studies have yielded inconsistent conclusions.
The purpose of this meta-analysis is to systematically analyze the effect of the number of parity on GBC risk.
We searched Web of Science, EMBASE, PubMed, China Biological Medicine Database from inception to the end of April 2015. Studies investigating parity and risk of GBC were included. A systematic review and a dose-response meta-analysis were performed to investigate the association between parity and GBC risk using odds ratios (OR) and 95 % confidence intervals (CI).
Thirteen case-control studies were eligible for inclusion in this meta-analysis, including a total of 2,164 cases and 11,340 controls. A significant association was identified for the ever parity vs. nulliparous at 1.39 (95 % CI 1.15-1.68; Power = 0.73; I (2) =0.0 %; P = 0.90). Similarly, the summary estimate for high vs. low parity number was 1.86 (95 % CI 1.51-2.30; Power = 0.26; I (2) = 66.0 % P < 0.01). For the dose-response relationship, a non-linear association between the parity number and GBC risk was not observed (P non-linearity = 0.578), but a clear linear relationship was detected. The combined odds ratio of GBC for an increase in parity of one live birth was 1.12 (95 % CI 1.09-1.21; Power = 0.99; I (2) = 39.9 %; P = 0.139). Subgroup and sensitivity analyses showed similar associations. No publication bias was found in all results. Significant heterogeneity between subgroups was detected by meta-regression analyses.
In females, higher parity may be associated with an increased risk of gallbladder cancer. In the future, high-quality cohort studies with larger sample sizes and randomized controlled trials are needed to fully scrutinize this association.