Body mass index and risk of renal cell cancer: a dose-response meta-analysis of published cohort studies.

Obesity is accepted as one of the major risk factors for renal cell cancer (RCC). However, conflicting results persist for the pooled risks based on the results from case-control and cohort studies combined, and the exact shape of the dose-response relationship has not been clearly defined yet. To help elucidate the role of obesity, PubMed and Embase databases were searched for published cohort studies on associations between body mass index (BMI) and risk of RCC. Random-effects models and dose-response meta-analyses were used to pool study results. Subgroup analyses were conducted by the available characteristics of studies and participants. Cohort studies (21) with 15,144 cases and 9,080,052 participants were identified. Compared to normal weight, the pooled relative risks and the corresponding 95% confidence intervals of RCC were 1.28(1.24-1.33) for preobesity and 1.77(1.68-1.87) for obesity, respectively. A nonlinear dose-response relationship was also found for RCC risk with BMI (p = 0.000), and the risk increased by 4% for each 1 kg/m(2) increment in BMI. There was no significant between-study heterogeneity among studies (I(2) = 35.6% for preobesity and I(2) = 44.2% for obesity, respectively). Subgroup analysis showed a basically consistent result with the overall analysis. These results suggest that increased BMI are associated with increased risk of RCC both for men and women.