Meta-analysis: Circulating adiponectin levels and risk of colorectal cancer and adenoma

OBJECTIVE: To provide a systematic review with a meta-analysis for addressing the association between circulating adiponectin levels and the risk of colorectal cancer and adenoma. METHODS: Multiple electronic sources including MEDLINE, EMBASE and the Science Citation Index Expanded databases were searched to identify relevant studies for this systematic review. All existing observational studies that examined the relationship between circulating adiponectin and colorectal cancer or adenoma were included. Weighted mean difference and 95% confidence intervals (CI) were estimated and pooled using meta-analysis methods. RESULTS: Overall 13 case control or nested case control studies met the inclusion criteria. A total of 6175 participants and 3015 cases of colorectal cancer and adenoma were included in this meta-analysis. The weighted mean difference (95% CI) were -1.084 mu g/mL (-1.836, -0.331), P = 0.005 in colorectal cancer and -1.43 mu g/mL (-2.231, -0.628), P = 0.000 in adenoma. In men, a 2% decreased risk of colorectal neoplasm for a 1 mu g/mL increment in adiponectin levels was observed (OR = 0.98, 95% CI 0.96-0.99) whereas among women there is no evidence of such a trend (OR = 0.99, 95% CI 0.97-1.01). CONCLUSIONS: Patients with colorectal cancer and adenoma demonstrated markedly lower adiponectin values than controls, yet there was significant heterogeneity among studies. A negative dose response relationship between levels of adiponectin and the risk of colorectal neoplasm was observed in men.