title: Does increased urination frequency protect against bladder cancer?
abstract: Experimental studies suggest that increased urination frequency may reduce bladder cancer risk if carcinogens are present in the urine. Only 2 small studies of the effect of increased urination frequency on bladder cancer risk in humans have been conducted with conflicting results. Our purpose was to evaluate the effect of urination frequency on risk of bladder cancer in a large, multicenter case-control study. We analyzed data based on interviews conducted with 884 patients with newly diagnosed, bladder cancer and 996 controls from 1998 to 2001 in Spain. We observed a consistent, inverse trend in risk with increasing nighttime voiding frequency in both men (p = 0.0003) and women (p = 0.07); voiding at least 2 times per night was associated with a significant, 40-50% risk reduction. The protective effect of nocturia was apparent among study participants with low, moderate and high water consumption. The risk associated with cigarette smoking was reduced by nocturia. Compared with nonsmokers who did not urinate at night, current smokers who did not urinate at night had an OR of 7.0 (95% CI = 4.7-10.2), whereas those who voided at least twice per night had an OR of 3.3 (95% CI = 1.9-5.8) (p value for trend = 0.0005). Our findings suggest a strong protective effect of nocturia on bladder cancer risk, providing evidence in humans that bladder cancer risk is related to the contact time of the urothelium with carcinogens in urine. Increased urination frequency, coupled with possible dilution of the urine from increased water intake, may diminish the effect of urinary carcinogens on bladder cancer risk.
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Department of Health and Human Services, Bethesda, MD 20892, USA. silvermd@mail.nih.gov
authors.forename: Debra T
authors.initials: DT
authors.lastname: Silverman
authors.forename: Juan
authors.initials: J
authors.lastname: Alguacil
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Rothman
authors.forename: Francisco X
authors.initials: FX
authors.lastname: Real
authors.forename: Montserrat
authors.initials: M
authors.lastname: Garcia-Closas
authors.forename: Kenneth P
authors.initials: KP
authors.lastname: Cantor
authors.forename: Nuria
authors.initials: N
authors.lastname: Malats
authors.forename: Adonina
authors.initials: A
authors.lastname: Tardon
authors.forename: Consol
authors.initials: C
authors.lastname: Serra
authors.forename: Reina
authors.initials: R
authors.lastname: Garcia-Closas
authors.forename: Alfredo
authors.initials: A
authors.lastname: Carrato
authors.forename: Josep
authors.initials: J
authors.lastname: Lloreta
authors.forename: Claudine
authors.initials: C
authors.lastname: Samanic
authors.forename: Mustafa
authors.initials: M
authors.lastname: Dosemeci
authors.forename: Manolis
authors.initials: M
authors.lastname: Kogevinas
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002273:Carcinogens / Q000032:analysis; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012907:Smoking / Q000652:urine; D001749:Urinary Bladder Neoplasms / Q000517:prevention & control*; D014554:Urination
chemical_list: D002273:Carcinogens