Normative bladder diary measurements: night versus day.

AIMS: To investigate bladder diary measurements from asymptomatic subjects in separate night and day periods, including their relationships to age and total volume voided. A major objective of this study was to generate age-adjusted reference values against which clinical measurements of nocturia can be compared.

MATERIALS AND

METHODS

Three-day bladder diaries were collected from 161 females and 92 males (age: median=46.5 years; range=19.6-84.6 years). We studied: average volume voided ("Vavg"), voiding frequency, and four urine production measures (volume, production rate, and their ratios to 24-hr values)

RESULTS

Both day and night Vavg and frequency increase with increasing volume. The night increase is much steeper than the day increase. With aging, frequency increases, Vavg decreases, day production decreases and night production increases. These age effects are steeper for males than females. Adjusting for age by regression analysis reduces the night production measure's variability by about 40%, and expressing production rate as a percent of the 24-hr value reduces the variability by an additional 20%.

CONCLUSIONS

We present regression equations that can be used to adjust night and day Vavg frequency and production rate reference values for the influences of age and total volume. Using these equations, we calculated a table of 95% confidence limits of night urine production and night frequency. The least variable night urine volume measurement studied was night/24-hr production rate; hence this may prove to be the most efficacious measurement to use in detecting nocturnal polyuria.