Drinking, micturition habits, and urine concentration as potential risk factors in urinary bladder cancer.

Investigation of micturition and drinking habits in urban (n = 475) and rural (n = 156) working populations demonstrated less frequent micturition, decreased fluid intake, and a higher urine concentration in the urban as compared to the rural group. All these differences were significant (P less than .01) by multivariate analysis, adjusting for age and sex differences. Drinking and micturition habits were similar in both sexes, but urine concentration was significantly lower in females (P less than .01) in both the urban and rural groups. Incidence of bladder cancer is reportedly higher in urban versus rural populations and in males versus females, the differences being apparently unaccountable for by differences in smoking, an important risk factor for bladder cancer. Our findings of greater urine concentration and less frequent micturition (which augments urine contact with bladder epithelium) in high-risk groups for bladder cancer are consistent with the "urogenous contact hypothesis." This hypothesis associates the etiology of bladder cancer with prolonged exposure to urine, on the basis of studies indicating carcinogenicity of urine. Further studies should indicate whether frequent drinking and urination are effective preventive measures against bladder cancer.