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Background:Nonrestorative sleep (NRS), defined as insufficiently rested or refreshed sleep, is considered to play an important role in the development of depression. The aim of this study is to investigate the predictive ability of insomnia-related symptoms, including NRS, for incident depressive symptoms (DEPs) in a longitudinal manner., Methods:We used data of 1196 samples aged 18–64 years who participated in both the Hispanic Community Health Study/Study of Latinos conducted in 2008–2010 and the follow-up study (Sueño Ancillary Study) conducted in 2010–2013. DEPs and insomnia-related symptoms (difficulty initiating sleep [DIS], difficulty maintaining sleep [DMS], early morning awakening [EMA], difficulty returning to sleep [DRS], and NRS) were evaluated by the 10-item Center for Epidemiologic Studies Depression Scale and the Women's Health Initiative Insomnia Rating Scale, respectively. A logistic regression analysis was used to evaluate the predictive ability of each insomnia-related symptom at baseline for incident DEPs in couple-years., Results:In the univariate logistic regression analysis, all insomnia-related symptoms had significant associations with incident DEPs (DIS, odds ratio [OR] = 1.6; DMS, OR = 1.6; EMA, OR = 1.5; DRS, OR = 1.9; NRS, OR = 2.5). After adjusting for sociodemographic factors and the confounding effects of other insomnia-related symptoms, only NRS (OR = 2.2, 95% confidence interval = 1.4–3.5, p = .001) was significantly associated with incident DEPs., Conclusions:NRS was a risk factor for incident DEPs, which includes a predictive ability for other insomnia-related symptoms. Our results suggest that focusing on NRS is an effective strategy for preventing depression in public health promotions.

ObjectivesThe current study examined the relationship between subjective SOL, sleep structure, changes in skin and body temperature, and subjective evaluation in healthy young adults to elucidate the pathophysiological mechanisms of insomnia.MethodsTwenty-eight participants (mean age: 21.5 ± 0.5 years) with no sleep problems participated in a 1-hour polysomnographic recording that obtained objective sleep parameters during the daytime while skin and body temperatures were recorded. The distal–proximal skin temperature gradient (DPG) was calculated. Subjective parameters, such as subjective SOL, sleep time, and restorative sleepiness, were evaluated before and after sleep.ResultsMost participants estimated their sleep latency as being longer than their actual SOL (13.7 min vs. 7.6 min). Objective SOL was significantly correlated with each sleep stage parameter whereas subjective SOL was negatively correlated with stage N2 sleep duration (Rho = −0.454, p = 0.020), slow-wave activity and delta power (Rho = −0.500, p = 0.011, Rho = −0.432, p = 0.031, respectively), and ΔDPG (the degree of reduction of heat loss before and after lights-off). Stepwise regression analysis showed that ΔDPG was the strongest predictive factor in explaining the length of subjective SOL.ConclusionsThe degree of heat dissipation before falling asleep contributed most to the sensation of falling asleep in healthy young adults. This finding may be helpful for elucidating the physiological mechanisms of insomnia and its treatment.STATEMENT OF SIGNIFICANCEThe time estimate ability is also activated during sleep. However, some insomniacs have abnormalities in this function and suffer from sleep state misperception, which is a discrepancy between subjective and objective sleep time. They often overestimate the sleep onset latency. We investigated the relationship between subjective sleep onset latency, sleep structure, EEG frequency components, and body temperature during the process of falling asleep in healthy adults. It was suggested that the Stage N2 duration, the amounts of slow wave activity around after lights-out, and the degree of heat dissipation before falling asleep may be related to the perception of falling asleep. These results are expected to contribute to the understanding of the pathophysiological mechanisms and to the treatment of insomnia.

Introduction Associations of sleep duration with health outcomes could differ depending on whether sleep is restorative. Age-related changes in the relationship between sleep need and sleep opportunity could also influence these associations. Methods Using data from 5804 participants of the Sleep Heart Health Study, a multicenter population-based prospective cohort study, we examined the longitudinal association of feeling rested after sleep combined with in-home polysomnographymeasured total sleep time (TST) or time in bed (TIB) with allcause mortality. Results A total of 223 (7.1%) and 991 (37.0%) deaths were reported in 3128 middle-aged (40–64 years) and 2676 older adults (≥ 65 years) with a mean (standard deviation) age of 54.5 (6.6) and 73.3 (5.7) years at baseline over a median (interquartile range) follow-up time of 12.3 (11.3–13.5) and 11.3 (8.2–12.2) years, respectively. Among middleaged adults, compared with the interquartile TST range (331 to < 414 min) with feeling rested, the lowest TST quartile (< 331 min) with feeling unrested was associated with higher mortality (adjusted hazard ratio [aHR], 1.54; 95% confidence interval [CI] 1.01–2.33); the highest TST quartile (≥ 414 min) with feeling rested was associated with lower mortality, independently from health and sleep covariates (aHR, 0.55; 95% CI 0.32–0.97). Among older adults, TIB, but not TST, was consistently associated with mortality. Compared with the interquartile TIB range (404 to < 482 min) with feeling rested, the highest TIB quartile (≥ 482 min) with feeling unrested was associated with higher mortality (aHR, 1.57; 95% CI 1.23–2.01). Conclusion The results suggest the role of restorative sleep in differentiating the effects of sleep duration on mortality outcomes for middle-aged and older adults. Our findings further suggest that there is a need to change the way to optimize sleep hygiene according to age groups: in middle-aged adults maintaining a substantial amount of sleep is more critical, whereas in older adults optimizing sleep opportunity is more critical to determine the sleep–mortality relationship. Support (if any) This work was supported by the Ministry of Health, Labor and Welfare, Government of Japan (Grant numbers #19FA1009 and #21FA1002).

Introduction There is evidence for a mismatch between subjective and objective sleep durations not only in individuals with insomnia but also in healthy individuals . However, it is unclear how such discrepancy impacts long-term health outcomes. This study investigated whether and how the discrepancy between subjective and objective sleep duration affected all-cause mortality in a sample of community-dwelling older adult men, aged ≥ 65 years. Methods We conducted a secondary analysis of data obtained via the Osteoporotic Fractures in Men Sleep Study, a community-based, longitudinal, observational, and multicenter study. We included data from 2,674 individuals who underwent an in-home polysomnography, completed morning surveys to assess subjective sleep duration during the polysomnography, and for whom survival or death data were available. We assessed the longitudinal association between misperception index (MI), calculated as MI = (objective sleep duration – subjective sleep duration) / objective sleep duration, and all-cause mortality. MI was treated as both a continuous and categorical predictor: the lowest (≤ -0.19; the overestimation of sleep duration) and highest MI quartiles (> 0.08; the underestimation of sleep duration) were compared to the interquartile range of MI (-0.19 Results During the follow-up with a mean (standard deviation) of 10.8 (4.2) years, 1,596 deaths (59.7%) were observed. As a continuous variable, MI showed a negative association with all-cause mortality after adjusting for multiple covariates, including polysomnography-measured objective sleep duration (fully adjusted hazard ratio [HR], 0.69; 95% confidence interval [CI], 0.56–0.84). As a categorical variable, the lowest MI quartile (vs. the interquartile MI range) was associated with increased mortality (fully adjusted HR, 1.28; 95% CI, 1.12–1.46), whereas the highest MI quartile was not associated with mortality (fully adjusted HR, 0.97; 95% CI, 0.85–1.11). Conclusion The subjective overestimation (“reverse” misperception) of sleep duration, may be a risk factor for all-cause mortality in older men. Further investigations are needed to examine physiological mechanisms through which subjective overestimation of sleep duration leads to negative long-term health outcomes. Support (if any) This work was supported by the Ministry of Health, Labor and Welfare, Government of Japan (Grant numbers #19FA1009 and #21FA1002).

Introduction Humans can estimate the time that has elapsed during sleep (time estimation ability; TEA). Although research on the TEA during sleep has advanced in the field of sleep research, few studies have focused on the relationship between the subjective sleep onset latency (SOL), which is an indicator of TEA, and objective sleep structures, body heat loss, and body temperature. This paper investigates the association of the subjective SOL with sleep structures such as the objective SOL, duration of each sleep stage, subjective sleep parameters, and body heat loss in healthy young participants. Methods Twenty six participants (7 men and 19 women, mean age of 21.5 ± 0.5 years) having no sleep problems participated in a 1-hour polysomnographic recording that obtained objective sleep parameters during the daytime while temperatures of the skin (i.e., dorsum of the hand and foot, forehead, and subclavian) and eardrum were recorded at intervals of 1 min. The distal–proximal skin temperature gradient (DPG), which is a good predictor of body heat loss and sleepiness, was calculated. Subjective parameters, such as the subjective SOL, sleep time, sleep depth, sleepiness, and mood, were evaluated before and after sleep. We examined the association of the subjective SOL with objective sleep parameters, DPG, and other subjective parameters. Results Most participants estimated their sleep latency to be longer than their actual SOL (mean objective SOL of 7.6 min vs. subjective SOL of 13.7 min). The objective SOL was significantly correlated with each sleep stage parameter whereas the subjective SOL was negatively correlated with the stage N2 sleep duration (Rho = −0.454, p = 0.020) and correlated with the stage N2 sleep latency (Rho = 0.402, p = 0.051). Participants who estimated a shorter subjective SOL had a higher DPG before sleep periods than that after sleep onset (Rho = −0.692, p < 0.001). Additionally, the subjective SOL was correlated with the subjective sleep depth, subjective wake after sleep onset, and restorative sleep. Conclusion The subjective sleep onset latency in the healthy young participants was affected by the degree of body heat loss before sleep onset and stable shallow nonrapid-eye-movement sleep. Support (If Any)