Hypertension and obesity and the risk of kidney cancer in 2 large cohorts of US men and women.

Kidney cancer incidence is increasing globally. Reasons for this rise are unclear but could relate to obesity and hypertension. We analyzed longitudinal relationships between hypertension and obesity and kidney cancer incidence in 156 774 participants of the Women's Health Initiative clinical trials and observational studies over 10.8 years. In addition, we examined the effect of blood pressure (BP) on kidney cancer deaths for over 25 years among the 353 340 men screened for the Multiple Risk Factor Intervention Trial (MRFIT). In the Women's Health Initiative, systolic BP (SBP) was categorized in 6 groups from <120 to >160 mm Hg, and body mass index was categorized using standard criteria. In age-adjusted analyses, kidney cancer risk increased across SBP categories (P value for trend <0.0001) and body mass index categories (P value for trend <0.0001). In adjusted Cox proportional hazards models, both SBP levels and body mass index were predictors of kidney cancer. In the MRFIT sample, there were 906 deaths after an average of 25 years of follow-up attributed to kidney cancer among the 353 340 participants aged 35 to 57 years at screening. The risk of death from kidney cancer increased in a dose-response fashion with increasing SBP (hazard ratio, 1.87 for SBP>160 versus <120 mm Hg; 95% confidence interval, 1.38-2.53). Risk was increased among cigarette smokers. Further research is needed to determine the pathophysiologic basis of relationships between both higher BP and the risk of kidney cancer, and whether specific drug therapies for hypertension can reduce kidney cancer risk.