The effect of hypertension on the risk for kidney cancer in Korean men

Background. The role of hypertension as a kidney cancer risk factor remains unclear. The objectives of this study were to prospectively examine the effects of hypertension on kidney cancer death, and to determine the synergistic effect of hypertension and smoking on kidney cancer risk. Methods. The cohort was composed of 576,562 Korean men, aged 30 and older, who received health insurance from the National Health Insurance Corporation, and who underwent biennial medical evaluations in 1992 and 1994. At baseline, 343,132 men (59.5%) were identified as current cigarette smokers. Between 1995 and 2001, there were 92 deaths from kidney cancer (2.2/100,000 person years). Using deaths from kidney cancer as the main outcome variable, Cox proportional hazards models were tested while controlling for age and other covariates. Results. An initial finding indicated that hypertension increased the mortality risk of kidney cancer [relative risk (RR) 2.43; 95% confidence interval (CI) 1.57-3.76]. After stratification of smoking status, RR for hypertension on kidney cancer was still increased for current smokers (RR 2.80; 95% CI 1.64-4.79). For current smokers, those with systolic blood pressure greater than or equal to160 mm Hg had a risk of kidney cancer that was 8.18 (95% CI, 3.13-21.36) times higher than those with a pressure less than 120 mm Hg. When the interaction term was included in the multivariate model, there was no significant synergistic effect of hypertension with current smoking on the risk of death from kidney cancer. Conclusion. This study supports the hypothesis that hypertension is an independent risk factor of kidney cancer mortality.