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Fluid balance

J M Miller et al, 2022. Fluids affecting bladder urgency and lower urinary symptoms: results from a randomized controlled trial, International Journal of Urogynecology

April 21, 2022


Introduction and hypothesis:
Caffeinated, alcoholic, artificially sweetened, carbonated, and acidic beverages are pervasive and consumed in large quantities. Reputedly, these beverages are "irritating to the bladder" and result in heightened void frequency, but prior studies lack control for intake volume. We tested the null hypothesis that women recruited from the community who demonstrate overactive bladder symptoms will show no difference by groups in void frequency when one group is instructed to replace listed beverages by substituting non-irritants (emphasis on water or milk) and the other group is instructed in healthy eating.

This was a parallel-group randomized controlled trial design with a three-period fixed sequence (baseline and 2 and 6 weeks post-baseline). We recruited 105 community women with overactive bladder symptoms.

Inclusion criteria:
>7 voids per day or 2 voids per night, daily intake of ≥16 oz. (473 ml) of beverages containing the ingredients listed above, and ≥ 32 oz. (946 ml) of total fluid intake. Stratified randomization was conducted. The primary outcome was average daily void frequency on a 3-day diary.

Participants were 86% white, mean (SD) age was 46.6 (17.6) years, and baseline void frequency was 9.2 (2.9) voids per day. At 2 and 6 weeks, estimated average (SD) difference in void frequency between group 1 and group 2 was -0.46 (0.57) and -0.31 (0.57) voids per day (p > 0.05); the null hypothesis was not rejected.

Women who reduce potentially irritating beverages while maintaining total fluid volume intake is not predictive of void frequency. Further research on type and volume of beverage intake is recommended.

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