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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).

A discrepancy in subjective and objective estimations of sleep duration, which often diverge, could have long-term adverse effects on health outcomes in older adults. Using data from 2674 older adult men (≥ 65 years of age) of the Osteoporotic Fractures in Men Sleep Study, 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. During the follow-up with a mean (standard deviation) of 10.8 (4.2) years, 1596 deaths were observed. As a continuous variable, MI showed a linear relationship 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). The subjective overestimation of sleep duration may be a risk factor for all-cause mortality in older men. Future studies should examine why subjective overestimation of sleep duration is associated with all-cause mortality from a physiological perspective.

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)

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.

The effects of exercise on sleep have been explored from various perspectives, but little is known about how the effects of acute exercise on sleep are produced through physiological functions. We used a protocol of multiple daytime sessions of moderate-intensity aerobic exercise and examined the subsequent effects on sleep structure, core body temperature (CBT), distal-proximal skin temperature gradient (DPG), and subjective parameters. Fourteen healthy men who did not exercise regularly were evaluated under the baseline (no exercise) and exercise conditions on a within-subject crossover basis. Under the exercise condition, each participant performed a 40-min aerobic workout at 40% of maximal oxygen intake, four times between morning and early evening. We observed a 33% increase in slow-wave sleep (SWS; P = 0.005), as well as increases in slow-wave activity (SWA; P = 0.026), the fast-sigma power/SWA ratio ( P = 0.005), and subjective sleep depth and restorativeness the following morning. Moreover, both CBT and the DPG increased during sleep after exercise ( P = 0.021 and P = 0.047, respectively). Regression analysis identified an increased nocturnal DPG during sleep after exercise as a factor in the increase in SWA. The fast-sigma/SWA ratio correlated with CBT. The performance of acute exercise promotes SWS with nocturnal elevation in the DPG. Both CBT and fast-sigma power may play a role in the specific physiological status of the body after exercise.NEW & NOTEWORTHY We used multiple daytime sessions of moderate-intensity aerobic exercise to examine the effects on the sleep structure, core body temperature (CBT), distal-proximal skin temperature gradient (DPG), and subjective parameters. Significant increases in slow-wave activity (SWA), CBT, DPG, fast-sigma power, and subjective parameters were observed during the night and the following morning. Nocturnal DPG is a factor in the increased SWA.

Periocular skin warming reportedly improves the objective and subjective sleep quality in adults with mild difficulty in falling asleep. To clarify the effects of periocular warming, we examined the distal skin temperatures (hands and feet), proximal skin temperature (infraclavicular region) and core body temperature as well as the distal-proximal skin temperature gradient (DPG). Nineteen healthy males underwent two experimental sessions, wherein they used a warming or sham eye mask under a semi-constant routine protocol in a crossover manner. Participants were instructed to maintain wakefulness with their eyes closed for 60 minutes after wearing the eye mask. The warming eye mask increased the periocular skin temperature to 38–40 °C for the first 20 minutes, whereas the temperature remained unchanged with the sham mask. Compared to that of the sham eye mask, the warming eye mask significantly increased the temperatures of the hands and feet and the DPG, whereas the proximal skin and core body temperatures were unaffected. Subjective sleepiness and pleasantness were significantly increased by the warming eye mask. These results represent physiological heat loss associated with sleep initiation without affecting the proximal skin or core body temperatures, suggesting that thermal stimulation in certain areas can provoke similar changes in remote areas of the body.

Research indicates that both acute and chronic physical activity improve sleep. Effects on sleep include prolongation of total sleep time, slow wave sleep increase, rapid eye movement sleep decrease, wake after sleep onset reduction, and shortened sleep latency. However, detailed biological mechanisms of these effects have not been well elucidated. Past studies strongly suggest that the sleep-promoting effect of exercise could be multifactorial. Increase of slow wave sleep, which has been repeatedly reported, strongly suggests physical activity effects on central nervous system function. Physical activity also elevates body temperature, alters glucose, and impacts other metabolic regulations. Habitual exercise also alters autonomic nervous system predominance measured by heart rate variability.

Periodic limb movements during sleep (PLMS) sometimes newly appear on the night of continuous positive airway pressure (CPAP) titration in patients with obstructive sleep apnea syndrome (OSAS). To ascertain the incidence and causative factors of this phenomenon, we investigated differences in its prevalence and the factors associated with newly appeared and persistent PLMS on CPAP titration night. We retrospectively analyzed polysomnographic data of 997 consecutive OSAS outpatients who had undergone overnight CPAP titration. On the basis of changes in periodic limb movements index (PLMI) values (cut off level≥15/h) from baseline polysomnography (BPSG) to CPAP titration PSG, patients were assigned to one of four groups: persistent, CPAP-emergent, CPAP-disappeared, and non-PLMS. The rate of patients was 6.7% in the persistent group, 8.0% in the CPAP-emergent group, 4.0% in the CPAP-disappearance group, and 81.2% in the non-PLMS group. Multivariate logistic regression analysis revealed that a higher apnea-hypopnea index (AHI) on BPSG and ≥47years of age appeared to be associated with the CPAP-emergent group. The results suggest that elderly patients with higher AHI at BPSG may present with CPAP-emergent PLMS.

Humans have the ability to estimate the passage of time in the absence of external time cues. In this study, we subjected 22 healthy males (aged 21.8±1.9 years) to a 40-min nap trial followed by 80min of wakefulness repeated over 28h, and investigated the relationship between various sleep parameters and the discrepancy (ΔST) of time estimation ability (TEA) during sleep, defined by the difference between actual sleep time (ST) and subjective sleep time (sub-ST) in each nap interval. Both ST and sub-ST were significant diurnal fluctuations with the peak in the early morning (9h after dim-light melatonin onset time, 2h after nadir time of core body temperature rhythm), and subjective sleep duration was estimated to be longer than actual times in all nap intervals (sub-ST>ST). There were significant diurnal fluctuations in discrepancy (sub-ST-ST) of TEA during sleep, and the degree of discrepancy correlated positively with increase in the amount of REM sleep and decrease in the amount of slow-wave sleep. These findings suggest that human TEA operates at a certain level of discrepancy during sleep, and that this discrepancy might be related to the biological clock and its associated sleep architecture.

Objective To clarify the prevalence of restless legs syndrome (RLS) in the chronic kidney disease (CKD) population and determine the relationship between severity of renal dysfunction and risk of RLS as well as the impact of the disorder on mood and sleep disturbance, we conducted a questionnaire survey followed by face-to-face interviews with Japanese CKD patients. Methods We sent a questionnaire battery including demographics items, the National Institutes of Health/International RLS Study Group (IRLSSG) consensus questionnaire, the Center for Epidemiological Studies Depression Scale, and the Pittsburgh Sleep Quality Index to eligible CKD patients ( n =514) and age- and sex-matched controls ( n =535). Structured interviews were performed for the diagnosis of RLS. Results The prevalence of positive RLS in the CKD subjects was significantly higher than that in the controls (3.5% vs. 1.5%, p =0.029). The proportion of renal failure (RF) in CKD subjects with RLS was significantly higher than in those without RLS, and multiple logistic regression analysis revealed that the presence of RLS symptoms was associated only with the existence of RF. In addition, the presence of both RLS and CKD was significantly associated with the presence of depression and sleep disturbance. Conclusions The risk of RLS in the CKD population was higher than that in the general population and increased with the progression of renal dysfunction. Additionally, the existence of RLS might play a role in an increased risk for developing depression and sleep disturbance in the CKD population.

Although evening preference has recently been identified as a risk factor for depression, it has not been substantiated whether evening preference is a direct risk factor for depressive states, or if it is associated secondarily through other factors, such as delayed sleep timing and shortened sleep duration. The objective of this study is to investigate associations in Japanese adult subjects between evening preference and incidence of depressive states, adjusting for various sleep parameters related to depressive states. The Morningness-Eveningness Questionnaire (MEQ), the Pittsburgh Sleep Quality Index (PSQI), and the Center for Epidemiologic Studies Depression Scale (CES-D) were administered to 1170 individuals (493 males/677 females; mean and range 38.5 and 20–59 yrs) to assess their diurnal preferences, sleeping states, and presence of depression symptoms. Subjects were classified into five chronotypes based on MEQ scores. Evening preference was associated with delayed sleep timing, shortened sleep duration, deteriorated subjective sleep quality, and worsened daytime sleepiness. Logistic regression analysis demonstrated that the extreme evening type (odds ratio [OR] =1.926, p=.018) was associated with increased incidence of depressive states and that the extreme morning type (OR=0.342, p=.038) was associated with the decreased incidence of depressive states, independent of sleep parameters, such as nocturnal awakening (OR=1.844, p

The present study was conducted to clarify the prevalence of non-pharmacological self-management (nPSM) practices for obtaining good sleep and to identify favorable nPSM practices that could be applied for reducing excessive daytime sleepiness (EDS). We analyzed epidemiological data for an authentic representative sample of the Japanese population.Data obtained from 24,686 adults via a self-administered questionnaire completed in the Active Survey of Health and Welfare 2000 were used for analyses. The prevalence of individual nPSM practices was calculated by gender. Subsequently, the associations between such practices and EDS were examined using logistic regression analyses."Having a bath" was the most prevalent nPSM practice for both men (59.0%) and women (64.4%), followed by "maintaining a regular schedule" (men: 49.0%, women: 58.6%), "reading or listening to music" (men: 43.4%, women: 49.4%), "snacking on food and/or beverages" (men: 36.1%, women: 27.9%), and "exercising" (men: 26.2%, women: 29.4%). The prevalence of "maintaining a regular schedule" increased with age. Multiple logistic regression analyses revealed that having a bath and maintaining a regular schedule had negative associations with EDS, whereas snacking on food and/or beverages had a positive association.Having a bath and maintaining a regular schedule were identified as favorable nPSM practices for reducing EDS, whereas snacking on food and/or beverages was considered to be an unfavorable nPSM practice.

Humans have the ability to estimate the amount of time that has elapsed during sleep (time estimation ability; TEA) that enables a subset of individuals to wake up at a predetermined time without referring to a watch or alarm clock. Although previous studies have indicated sleep structure as a key factor that might influence TEA during sleep, which sleep parameters could affect the TEA has not been clarified. We carried out an experimental study in which 20 healthy volunteers participated in six time estimation trials during the 9-h nighttime sleep (NS) experiment or daytime sleep (DS) experiment. The time estimation ratio (TER, ratio of the subjective estimated time interval to actual time interval) decreased significantly from the first to the sixth trial in both the NS and DS experiments. TER correlated positively with slow wave sleep (SWS) in both experiments, suggesting that SWS was a determining factor in accurate time estimation, irrespective of circadian phase they slept. No other sleep parameters showed steady influence on TEA. The present findings demonstrate that longer period of SWS is associated with the longer sleep time they subjectively experienced during sleep.