Voiding frequency in a sample of asymptomatic American men.

PURPOSE: There are sparse published data concerning the urinary habits of asymptomatic American men. We studied those urinary habits, as revealed by a 24-hour voiding diary.
MATERIALS AND METHODS: Men without lower urinary tract symptoms completed the International Prostate Symptom Score (I-PSS) and a 24-hour voiding diary. Demographic and diary data were analyzed using multivariate linear and logistic regression.
RESULTS: A total of 284 asymptomatic males 18 to 66 years old returned interpretable diaries. Subjects voided a median of 7 times in 24 hours (range 2 to 21) with 95% voiding fewer than 12 times daily. Median 24-hour urine volume was 1,650 ml (range 290 to 6,840). Median fluid intake was 2,747 ml (range 500 to 10,520). Of the men 82 (29%) reported at least 1 nocturic episode. The 24-hour frequency was related to total urine volume (beta = 1.2, p <0.001) and total fluid intake (beta = 0.1, p <0.001), inversely related to mean voided volume (beta = -1.1, p <0.001) and lower in white men (beta = 0.1, p <0.02) but independent of age and body mass index. The probability of nocturia was highly related to the nighttime diuresis rate (beta = 15, p <0.001), inversely related to mean voided volume (beta = 1, p = 0.001) and less likely in white men. Median I-PSS was 2 (range 0 to 22). I-PSS increased with age, body mass index and total urinary frequency, and it was lower in white men.
CONCLUSIONS: This study suggests that the threshold of 8 to define abnormal urinary frequency may not be correct since more than a third of our sample of asymptomatic men voided more than 8 times daily. It is probably inadvisable to apply a single set of normative values to all American men because of significant variability in regional climates and populations.