Derivation and validation of a symptom-anchored diagnostic criterion for nocturnal polyuria in women: aligning with aging physiology

Objectives: To investigate the physiological validity of current diagnostic criteria for nocturnal polyuria and to derive and validate a symptom-anchored revision consistent with female aging. Methods: This retrospective cross-sectional study analyzed 3-day bladder diaries from 3,000 women with lower urinary tract symptoms. We assessed age-specific nocturnal polyuria prevalence using current International Continence Society definitions (nocturnal polyuria index ≥33% for women >66 y and ≥20% for women ≤65 y). To address discrepancies with aging physiology, a novel cutoff was derived using the Youden index anchored to symptom bother (King’s Health Questionnaire nocturia severity score ≥1). The proposed composite definition (nocturnal polyuria index ≥28% plus symptom score ≥1) was validated using multivariable regression and randomized split-sample validation (training: n=2,500; validation: n=500). Results: Under current criteria, nocturnal polyuria prevalence was higher in younger women (75.5%) compared with older women (50.5%). Multivariable analysis identified age as a protective factor (odds ratio: 0.96; 95% CI: 0.95-0.97), inconsistent with physiology. Conversely, the proposed new definition identified age as a significant positive risk factor (odds ratio: 1.03; 95% CI: 1.02-1.04). Prevalence remained stable at 26.8% (one-in-four) in premenopausal women, rising linearly to 46.3% (one-in-two) in postmenopausal women. Internal validation confirmed model stability (area under curve: 0.86; 95% CI: 0.83-0.90). Conclusions: Current age-stratified thresholds of nocturnal polyuria result in discrepancies with aging physiology. The proposed framework establishes a physiologically plausible standard. By anchoring symptom bother score and nocturnal polyuria index of 28%, this definition facilitates the identification of symptomatic women and highlights the distinct impact of menopause.