Urinary Habits Among Asymptomatic Women

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Three hundred women with no urinary symptoms completed a 24-hour urine frequency-volume chart, using 300-ml graduated measuring cups to record fluid intake and urine volume. They also noted rising and retiring times. The women were a median of 40 years of age (range, 18-91 years) with a median body mass index of 26 kg/m 2 and a median parity of 2. Twenty-six (9%) had undergone a hysterectomy. One fourth of the women were postmenopausal, with two thirds of them taking hormone replacement therapy. Black and white women represented 39% of the population each, 12% were Hispanic, and 9% were Asian. One woman classified herself as mixed race. Her results were not reported in the racial comparisons. Data from the subjects' diaries are reported in Table 1. The median number of voids each day was 8 (range, 4-18). The women had a median of 4 voids per liter of fluid intake and a median of 5 urinations per liter voided. Three definitions of nocturnal polyuria were considered. Nocturnal polyuria was reported by 9% of subjects if the definition was nocturnal urine volume of >35% of the total 24-hour urine volume. When described as nighttime urine production of >0.9 ml/min, 41% of the women could be said to have nocturnal polyuria. If >6.6 ml/kg of urine production was considered to be nocturnal polyuria, this condition was reported by 29% women. Eighteen percent of the subjects had polyuria (total urine output >2500 ml 1 0 ). Linear regression analysis was performed considering all possible confounding variables, including race. Patient age was a statistical significant predictor of total voids per 24 hours (P<.001), number of voids per liter of fluid intake (P <.002), number of nighttime voids (P <.001), and daytime and nighttime diuresis (P <.001 for both). Black women had significantly lower mean urine volume (P <.001), maximum voided volume (P <.001), number of voids per liter of urine output (P <.001), and daytime and nighttime diuresis rates (P <.001 for both). Asian women had significantly higher parity (P =.002), and white women had significantly higher maximum voided volume (P =.002).