The Iwaki Health Promotion Project was a comprehensive study for the clarification of the etiology of lifestyle-related diseases such as hypertension, cardiovascular diseases, atherosclerosis, chronic renal failure, type 2 diabetes mellitus, obesity, metabolic syndrome in collaboration with the Hirosaki University, Hirosaki City, and Aomori Prefecture general screening center [1-6]. We evaluated sleep disturbance and nocturia using the Pittsburgh Sleep Quality Index (PSQI), and structured questionnaire for nocturia, respectively. Lower urinary tract symptoms were evaluated using international prostate symptom score (IPSS) for men, and overactive bladder symptom score (OABSS) for women. Sleep disturbance was defined as a PSQI score of ≥ 6. QOL was measured using the Short Form-36 questionnaire. Impacts of nocturia and sleep disturbance on QOL reduction (>30%) were investigated using logistic regression analyses.
Of the 3992 participants, 1529 were men and 2463 were women (mean age, 55 yr) in the present study. The frequency of nocturia (two or more voids per night) was 27% in men and 22% in women. Median IPSS in men and median OABSS in women were 5 (IQR: 1–10) and 1 (IQR: 0–3), respectively. Median PSQI score was 3 (IQR, 2–5).
Our results showed that sleep disturbance was observed in 16%. As expected, the higher frequency of nocturia was significantly associated with higher PSQI scores. In men, IPSS had a significant
association with general, physical, and mental QOL. In women, OABSS was significantly associated with general and physical QOL, but the association was not significant with mental QOL. PSQI scores were significantly associated with all QOL components. Frequencies of nocturia were significantly associated with general and physical QOL, but the association was not significant with mental QOL. These results suggest that nocturia and sleep disturbance affect QOL domains differently.
The inverse probability of treatment weighting (IPTW)–adjusted multivariate logistic regression analysis showed that nocturia was not
associated with a >30% reduction in general and mental QOL, whereas sleep disturbance was significantly associated with general, physical, and mental QOL reduction .
These results suggested the impact of nocturia and sleep disturbance on the physical component of QOL was significant, but this was not the case with the general mental component of QOL. It should be noted that impact of nocturia on mental component of QOL differ depends on the age of cohort. because nocturia and/or sleep disturbance may be more bothersome to a younger population than to an older population. We additionally investigated the impact of sleep disturbance and nocturia on QOL stratified by age between <65 (n = 2765, 69%) and ≥65 (n = 1227, 31%) yr. Our results suggested the relationship between nocturia and mental QOL in individuals aged ≥65 yr was not significant. From these results, the impacts of nocturia and sleep disturbance on QOL domains may differ among age groups.
Although it is no doubt that nocturia has been proved to have a negative impact on the QOL and sleep quality, it is difficult to conclude whether nocturia or sleep disturbance has a more detrimental effect on QOL reduction because of a complex triangular relationship between nocturia, sleep disturbance, and QOL. Two different hypotheses need to emerge when discussing nocturia and sleep disturbance whether an individual awakens because of a urinary urgency or sleep disturbance (unrelated to urinary urgency).
The population-based FINNO study  found that >50% of nocturia could be attributed to a specific sleep disorder. This observation suggests that two components of nocturia (urinary urgency and sleep inability) need to be analyzed to distinguish between cause and effect.
As this was a cross-sectional study, the causality of nocturia and sleep disturbance could not be assessed. Although a potential impact of nocturia on sleep disturbance and QOL has been suggested, identifying an independent relationship among nocturia, sleep disturbance, and QOL was challenging. Further study is necessary to determine whether our finding can be translated to other similar populations or not. Regardless of these limitations, our results support the importance of the association of nocturia and sleep quality with QOL.
In conclusion, nocturia was not associated with general and mental QOL reduction, whereas sleep disturbance was associated with general, physical, and mental QOL reduction.
Written by: Shingo Hatakeyama, MD, Assistant Professor, Department of Urology, Hirosaki University Graduate School of Medicine, Hirosaki, JAPAN
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