Obesity and kidney cancer risk in men: a meta-analysis (1992-2008)

We conducted a quantitative summary analysis to evaluate the recent evidence of kidney cancer risk according to body mass index (BMI) among men. The studies included in this quantitative review were all cohort and case-control studies, which provided information on kidney cancer risk associated with obesity/overweight, published between 1992 and 2008. The details of studies have been identified through searches on the MEDLINE database. We first estimated the risk associated with a unit increase in BMI (1 kg/m(2)) for individual studies using logit-linear model. After deriving the natural logarithm of the risk per unit of BMI for all studies, we calculated a pooled estimate and corresponding 95% confidence interval (CI) as a weighted average of the risk obtained in individual studies, by giving a weight proportional to its precision. A total of 27 studies (13 cohort studies and 14 case-control studies) that provided kidney cancer risk according to BMI in men were included in the present analysis. The strength of association was almost similar in most of the cohort studies (relative risk (RR) ranged from 1.04-1.06 per unit increase in BMI) and in one study RR was 1.08. There was no heterogeneity across studies (p-value= 0.164). The pooled risk was 1.05 (95% CI= 1.04-1.06) per unit increase in BMI based on the cohort studies. The present analysis confirmed the evidence of kidney cancer risk with increased BMI in men and obesity may be responsible at least in part for the rising incidence rates.