A Longitudinal Study of Bidirectional Relationships between Sleep Disorder and Frequency of Nocturia: Results from the Iwaki Health Promotion Project

Introduction: The causal relationship between sleep disorder and frequency of nocturia remains unclear. Methods: We longitudinally evaluated sleep disorder and frequency of nocturia in 547 community-dwelling adults between baseline and 5-year follow-up. We included participants ≥50 years old who have no sleep disorder (the Pittsburgh Sleep Quality Index [PSQI] ≥ 5) nor nocturia (≥1). For 5 years, we evaluated the temporal changes in sleep disorder and nocturia and the bidirectional relationships between sleep disorder and nocturia. Results: Of the 547 participants, we included 268 adults with a median age of 61 years in this study. Median PSQI and nocturia were significantly increased for 5 years from 2 to 3 and from 1 to 2, respectively. New onset of sleep disorder (PSQI > 5) and nocturia >1 was observed in 42 (16%) and 137 (51%) participants, respectively. The cross-lagged panel analysis showed that the path coefficient from PSQI to nocturia (β = 0.22, p = 0.031) was significantly higher than that from nocturia to PSQI (β = 0.02, p = 0.941). Conclusions: Our longitudinal study showed the effect of sleep disorder on nocturia was significant, although nocturia may not significantly worsen sleep disorder in community-dwelling adults.