This study aimed to determine whether both subjective sleep quality and sleep duration are directly associated with quality of life (QOL), as well as indirectly associated with QOL through insomnia symptoms. Individuals aged 20–69 years without mental illness (n = 9305) were enrolled in this web-based cross-sectional survey. The Short Form-8 was used to assess physical and mental QOL. We used the Pittsburgh Sleep Quality Index (PSQI) and extracted items related to subjective sleep quality and sleep duration. Insomnia symptoms were also extracted from the PSQI. The hypothesized models were tested using structural equation modeling. Worse sleep quality, but not shorter sleep duration, was related to worse physical QOL. Both worse sleep quality and shorter sleep duration were related to worse mental QOL. Insomnia symptoms mediated these relationships. Subgroup analyses revealed a U-shaped relationship between sleep duration and physical/mental QOL. However, the relationship between sleep quality and physical/mental QOL was consistent regardless of sleep duration. The results suggest that subjective sleep quality has a more coherent association with QOL than subjective sleep duration. Because of its high feasibility, a questionnaire on overall sleep quality could be a useful indicator in future epidemiological studies of strategies for improving QOL.

Working memory (WM) performance, which is an important factor for determining problem-solving and reasoning ability, has been firmly believed to be constant. However, recent findings have demonstrated that WM performance has the potential to be improved by repetitive training. Although various skills are reported to be improved by sleep, the beneficial effect of sleep on WM performance has not been clarified. Here, we show that improvement in WM performance is facilitated by posttraining naturalistic sleep. A spatial variant of then-back WM task was performed by 29 healthy young adults who were assigned randomly to three different experimental groups that had different time schedules of repetitiven-back WM task sessions, with or without intervening sleep. Intergroup and intersession comparisons of WM performance (accuracy and response time) profiles showed thatn-back accuracy after posttraining sleep was significantly improved compared with that after the same period of wakefulness, independent of sleep timing, subject's vigilance level, or circadian influences. On the other hand, response time was not influenced by sleep or repetitive training schedules. The present study indicates that improvement inn-back accuracy, which could reflect WM capacity, essentially benefits from posttraining sleep.

Long-term benzodiazepine (BZD) use is not recommended in the treatment of chronic insomnia, and psychosocial interventions, particularly cognitive behavioral therapy for insomnia (CBT-I), are a potential treatment option for discontinuing BZDs. This systematic review and meta-analysis aimed to clarify whether psychosocial interventions are effective for discontinuing BZD hypnotics in patients with chronic insomnia. A literature search of major electronic databases was conducted up to July 2018. Two researchers independently selected relevant publications, extracted data, and evaluated methodological quality according to the Cochrane criteria. Eight randomized-controlled trials, all of which evaluated CBT-I, were included in this review, and meta-analyses were performed. The results indicated that short-term (≤3 mo) CBT-I plus gradual tapering was more effective than gradual tapering alone for discontinuing BZDs hypnotics (risk ratio: 1.68, 95% confidence interval [CI]: 1.19-2.39, p = 0.003) and for improving insomnia symptoms (g: -0.69, 95% CI: -1.09 - -0.28, p = 0.0009). However, the long-term (12 mo) efficacy of CBT-I for discontinuing BZDs was not significant (risk ratio: 1.67, 95% CI: 0.91-3.07, p = 0.10). Thus, CBT-I is effective for discontinuing BZD hypnotics for ≤3 mo. Further studies are needed to clarify the long-term efficacy of psychosocial interventions for discontinuing BZD hypnotics.

Associations of sleep duration with human health could differ depending on whether sleep is restorative. Using data from 5804 participants of the Sleep Heart Health Study, we examined the longitudinal association of sleep restfulness combined with polysomnography-measured total sleep time (TST) or time in bed (TIB), representing different sleeping behaviors, with all-cause mortality. Among middle-aged adults, compared with restful intermediate TST quartile, the lowest TST quartile with feeling unrested was associated with higher mortality (hazard ratio [HR], 1.54; 95% confidence interval [CI] 1.01–2.33); the highest TST quartile with feeling rested was associated with lower mortality (HR, 0.55; 95% CI 0.32–0.97). Among older adults, the highest TIB quartile with feeling unrested was associated with higher mortality, compared with restful intermediate TIB quartile (HR, 1.57; 95% CI 1.23–2.01). Results suggest a role of restorative sleep in differentiating the effects of sleep duration on health outcomes in midlife and beyond.