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

We conducted a quantitative summary analysis to assess whether obesity carries higher relative risk in women than 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 values obtained in individual studies, by giving a weight proportional to its precision. A total of 28 studies (15 cohort studies and 13 case-control studies) provided kidney cancer risk according to BMI in women. The relative risks (RR), which showed statistical significance, ranged from 1.04 to 1.12 per unit increase in BMI in various cohort studies. The pooled risk was 1.06 (95% CI=1.05-1.07) per unit increase in BMI based on cohort studies. Among all the studies, which reported association in both men and women, the pooled risk was slightly higher in women. In conclusion, the present analysis reported slightly a higher kidney cancer risk due to obesity in women than men. Increasing prevalence of obesity with higher proportion among women may be responsible for the rising incidence rates in women.