Objective underpinnings of self-reported sleep quality in middle-aged and older adults: the importance of N2 and wakefulness

STUDY OBJECTIVES

The measurable aspects of brain function (polysomnography, PSG) that are correlated with sleep satisfaction are poorly understood. Using recent developments in automated sleep scoring, which remove the within- and between-rater error associated with human scoring, we examine whether PSG measures are associated with sleep satisfaction.

DESIGN AND SETTING

A single night of PSG data was compared to contemporaneously collected measures of sleep satisfaction with Random Forest regressions. Whole and partial night PSG data were scored using a novel machine learning algorithm.

PARTICIPANTS

Community-dwelling adults (N = 3165) who participated in the Sleep Heart Health Study.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Models explained 30% of sleep depth and 27% of sleep restfulness, with a similar top four predictors: minutes of N2 sleep, sleep efficiency, age, and minutes of wake after sleep onset (WASO). With increasing self-reported sleep quality, there was a progressive increase in N2 and decrease in WASO of similar magnitude, without systematic changes in N1, N3 or REM sleep. In comparing those with the best and worst self-reported sleep satisfaction, there was a range of approximately 30 min more N2, 30 min less WASO, an improvement of sleep efficiency of 7-8%, and an age span of 3-5 years. Examination of sleep most proximal to morning awakening revealed no greater explanatory power than the whole-night data set.

CONCLUSIONS

Higher N2 and concomitant lower wake is associated with improved sleep satisfaction. Interventions that specifically target these may be suitable for improving the self-reported sleep experience.

Nonparametric parameters of 24-hour rest-activity rhythms and long-term cognitive decline and incident cognitive impairment in older men

Altered 24-hour rest-activity rhythms may be associated with cognitive impairment in older adults, but evidence from prospective studies is limited. Non-parametric methods were used to assess actigraphy-based activity patterns in 2,496 older men. Incident cognitive impairment was assessed four times over 12 years using the Modified Mini Mental State Examination (3MS) and Trails B tests, self-reported medication use, and clinical diagnosis. The highest quartile (vs. the lowest) of intradaily variability and the lowest quartiles (vs. the highest) of interdaily stability and relative amplitude were associated with incident cognitive impairment ((Hazard ratio (95% confidence interval): 1.82 (1.31, 2.53)), 1.36 (0.99, 1.86), and 1.85 (1.33, 2.56), respectively). A larger increase in intradaily variability over 7.5 years was associated with a greater subsequent decline in 3MS scores but not in Trails B performance. In conclusion, less stable and more variable rest-activity rhythms may represent early biomarkers of cognitive impairment in older men.

Physiological correlates of the Epworth Sleepiness Scale reveal different dimensions of daytime sleepiness

The Epworth Sleepiness Scale is commonly used to examine self-reported daytime sleepiness in clinical populations; the physiologic correlates of this scale, however, are not well understood. Furthermore, how well this scale correlates with parallel objective and self-reported concepts of daytime sleepiness is not well described. As such, we used machine learning algorithms to examine the association between Epworth Sleepiness Scale scores and 55 sleep and medical variables in the Sleep Heart Health Study (N = 2105). Secondary analyses examined data stratified by age and gender and the relationship between the Epworth and other measures of daytime sleepiness. Analyses of the main data set resulted in low explained variance (7.15%-10.0%), with self-reported frequency of not getting enough sleep as most important predictor (10.3%-13.9% of the model variance). Stratification by neither age nor gender significantly improved explained variance. Cross-correlational analysis revealed low correlation of other daytime sleepiness measures to Epworth scores. We find that Epworth scores are not well explained by habitual or polysomnographic sleep values, or other biomedical characteristics. These analyses indicate that there are different, potentially orthogonal dimensions of the concept of "daytime sleepiness" that may be driven by different aspects of sleep physiology. As the physiologic correlates of the Epworth Sleepiness Scale remain to be elucidated, interpretation of the clinical meaning of these scores should be done with caution.

Heart rate and heart rate variability as outcomes and longitudinal moderators of treatment for pain across follow-up in Veterans with Gulf War illness

AIMS

Accumulating evidence suggests Gulf War illness (GWI) is characterised by autonomic nervous system dysfunction (higher heart rate [HR], lower heart rate variability [HRV]). Yoga - an ancient mind-body practice combining mindfulness, breathwork, and physical postures - is proposed to improve autonomic dysfunction yet this remains untested in GWI. We aimed to determine (i) whether HR and HRV improve among Veterans with GWI receiving either yoga or cognitive behavioural therapy (CBT) for pain; and (ii) whether baseline autonomic functioning predicts treatment-related pain outcomes across follow-up.

MAIN METHODS

We present secondary analyses of 24-hour ambulatory cardiac data (mean HR, square root of the mean squared differences between successive R-R intervals [RMSSD], high frequency power [HF-HFV], and low-to-high frequency ratio [LF/HF] extracted from a 5-min window during the first hour of sleep) from our randomised controlled trial of yoga versus CBT for pain among Veterans with GWI (ClinicalTrials.govNCT02378025; N = 75).

KEY FINDINGS

Veterans who received CBT tended towards higher mean HR at end-of-treatment. Better autonomic function (lower mean HR, higher RMSSD/HF-HRV) at baseline predicted greater reductions in pain across follow-up, regardless of treatment group. Better baseline autonomic function (mid-range-to-high RMSSD/HF-HRV) also predicted greater pain reductions with yoga, while worse baseline autonomic function (higher mean HR, lower RMSSD/HF-HRV) predicted greater pain reductions with CBT.

SIGNIFICANCE

To our knowledge, this is the first study to suggest that among Veterans with GWI, HR may increase with CBT yet remain stable with yoga. Furthermore, HR and HRV moderated pain outcome across follow-up for yoga and CBT.

Predicting incident dementia and mild cognitive impairment in older women with nonparametric analysis of circadian activity rhythms in the Study of Osteoporotic Fractures

STUDY OBJECTIVES

Disrupted daily rhythms are associated with mild cognitive impairment (MCI) and dementia. The specific nature of how rhythms and cognition are related, however, is unknown. We hypothesized characteristics from a nonparametric estimate of circadian rest-activity rhythm patterns would be associated to the development of MCI or dementia.

METHODS

Wrist actigraphy from 1232 cognitively healthy, community-dwelling women (mean age 82.6 years) from the Study of Osteoporotic Fractures was used to estimate rest-activity patterns, including intradaily variability (IV), interdaily stability (IS), most active 10-hour period (M10), least active 5-hour period (L5), and relative amplitude (RA). Logistic regression examined associations of these predictors with 5-year incidence of MCI or dementia. Models were adjusted for potential confounders.

RESULTS

Women with earlier sleep/wake times had higher risk of dementia, but not MCI, (early vs. average L5 midpoint: OR, 1.66; 95% CI, 1.08-2.55) as did women with smaller day/night activity differentials (low vs. high RA: OR, 1.96; 95% CI, 1.14-3.35). IV, IS, and M10 were not associated with MCI or dementia.

CONCLUSION

The timing and difference in day/night amplitude, but not variability of activity, may be useful as predictors of dementia.

Effect of artificial dawn light on cardiovascular function, alertness, and balance in middle-aged and older adults

STUDY OBJECTIVES

When arising in the morning, many older people experience dizziness and difficulty maintaining proper balance, as the cardiovascular system is not able to compensate to the postural shift (standing) and maintain sufficient blood flow to the brain. Such changes in cardiovascular function are observed in young individuals exposed to a dawn simulation light. In this study, we examined whether exposure to a dawn simulation light could impact cardiovascular function and consequent changes in balance in middle-aged and older adults.

METHODS

Twenty-three participants (67.3 ± 8.8 y), 12 of whom reported a history of dizziness in the morning, underwent two overnight stays in our laboratory. During both nights, they slept in complete darkness, except for the last 30 minutes of one of the nights during which a dawn simulation light was used. Continuous blood pressure (BP) and heart rate (HR) were monitored. Subjective and objective alertness, salivary cortisol, and mobile and standing balance were examined upon arising.

RESULTS

Dawn simulation light decreased (33%) the amount of sleep before morning awakening, lowered BP (6.24 mmHg), and increased HR (0.93 bpm). Despite these changes in physiology, there was no significant impact of dawn simulation on subjective or objective alertness, measures of standing or ambulatory balance, morning cortisol awakening response, or cardiovascular function after awakening.

CONCLUSION

While the dawn simulation did cause an increase in wake and a change in cardiovascular function prior to morning arousal in older adults, we could find no evidence of a functional change in either cardiovascular function or balance upon standing.

CLINICAL TRIAL

Registered on Clinicaltrials.gov, #NCT02632318, https://clinicaltrials.gov/ct2/show/NCT02632318.

Translation and Validation of a Chinese Version of the Cleveland Adolescent Sleepiness Questionnaire

PURPOSE

The Cleveland Adolescent Sleepiness Questionnaire was originally developed and published in English and has served as a valid and effective tool for the assessment of adolescents' experiences with sleepiness in a variety of situations. To allow for comparisons between sleepiness in adolescents from different cultures, and with different linguistic backgrounds, reliable and valid measurement tools are necessary. The purpose of this study was to translate and validate a Chinese version of the Cleveland Adolescent Sleepiness Questionnaire (C-CASQ).

MATERIALS AND METHODS

Sensitivity, specificity, internal consistency, and criterion validity data for the C-CASQ were tested using 458 adolescents in Taiwan. Data from 191 participants were used to establish internal consistency reliability and conduct exploratory factor analysis (EFA), while data from 267 participants were used to establish criterion validity and conduct confirmatory factor analysis (CFA). Initial criterion validity was established through a comparison of the C-CASQ with scores from the Chinese version of the Morningness-Eveningness Scale for Children, a measure of chronotype.

RESULTS

EFA resulted in four factors, consistent with the original English version of the CASQ, while CFA established goodness of fit. The scale demonstrated acceptable to good internal consistency (α = 0.77~0.86). Initial criterion validity was evident as the total score and each of the subscale scores on the C-CASQ was significantly higher (greater sleepiness) in evening-types.

CONCLUSION

The C-CASQ appears to be a psychometrically sound measure to evaluate sleepiness in Chinese-speaking adolescents.

The neurobiological underpinning of the circadian wake signal

The circadian wake drive is a mathematic representation of the observed increased propensity to stay awake late in the day, peaking in the hours just before anticipated bed time. It has been called the "forbidden zone" due to the difficulty in initiating sleep during this time and is responsible for the problems initiating sleep when traveling eastward, for maintaining daytime sleep in shift workers, and for initiating sleep in some individuals with insomnia. Evidence culled from studies in individuals with narcolepsy, who lack production of hypocretin (orexin) neuropeptides, as well as a primate model of human wake consolidation and pharmacologic studies of hypocretin antagonists indicate that hypocretin-1 may be the physiologic instantiation of the circadian wake drive. This review will discuss the evidence in support of this hypothesis.

A Temporal Threshold for Distinguishing Off-Wrist from Inactivity Periods: A Retrospective Actigraphy Analysis

(1) Background. To facilitate accurate actigraphy data analysis, inactive periods have to be distinguished from periods during which the device is not being worn. The current analysis investigates the degree to which off-wrist and inactive periods can be automatically identified. (2) Methods. In total, 125 actigraphy records were manually scored for ‘off-wrist’ and ‘inactivity’ (99 collected with the Motionlogger AMI, 26 (sampling frequency of 60 (n = 20) and 120 (n = 6) s) with the Philips Actiwatch 2.) Data were plotted with cumulative frequency percentage and analyzed with receiver operating characteristic curves. To confirm findings, the thresholds determined in a subset of the Motionlogger dataset (n = 74) were tested in the remaining dataset (n = 25). (3) Results. Inactivity data lasted shorter than off-wrist periods, with 95% of inactive events being shorter than 11 min (Motionlogger), 20 min (Actiwatch 2; 60 s epochs) or 30 min (Actiwatch 2; 120 s epochs), correctly identifying 35, 92 or 66% of the off-wrist periods. The optimal accurate detection of both inactive and off-wrist periods for the Motionlogger was 3 min (Youden’s Index (J) = 0.37), while it was 18 (J = 0.89) and 16 min (J = 0.81) for the Actiwatch 2 (60 and 120 s epochs, respectively). The thresholds as determined in the subset of the Motionlogger dataset showed similar results in the remaining dataset. (4) Conclusion. Off-wrist periods can be automatically identified from inactivity data based on a temporal threshold. Depending on the goal of the analysis, a threshold can be chosen to favor inactivity data’s inclusion or accurate off-wrist detection.

PSG Validation of minute-to-minute scoring for sleep and wake periods in a consumer wearable device

Background

Actigraphs are wrist-worn devices that record tri-axial accelerometry data used clinically and in research studies. The expense of research-grade actigraphs, however, limit their widespread adoption, especially in clinical settings. Tri-axial accelerometer-based consumer wearable devices have gained worldwide popularity and hold potential for a cost-effective alternative. The lack of independent validation of minute-to-minute accelerometer data with polysomnographic data or even research-grade actigraphs, as well as access to raw data has hindered the utility and acceptance of consumer-grade actigraphs.

Methods

Sleep clinic patients wore a consumer-grade wearable (Huami Arc) on their non-dominant wrist while undergoing an overnight polysomnography (PSG) study. The sample was split into two, 20 in a training group and 21 in a testing group. In addition to the Arc, the testing group also wore a research-grade actigraph (Philips Actiwatch Spectrum). Sleep was scored for each 60-s epoch on both devices using the Cole-Kripke algorithm.

Results

Based on analysis of our training group, Arc and PSG data were aligned best when a threshold of 10 units was used to examine the Arc data. Using this threshold value in our testing group, the Arc has an accuracy of 90.3%±4.3%, sleep sensitivity (or wake specificity) of 95.5%±3.5%, and sleep specificity (wake sensitivity) of 55.6%±22.7%. Compared to PSG, Actiwatch has an accuracy of 88.7%±4.5%, sleep sensitivity of 92.6%±5.2%, and sleep specificity of 60.5%±20.2%, comparable to that observed in the Arc.

Conclusions

An optimized sleep/wake threshold value was identified for a consumer-grade wearable Arc trained by PSG data. By applying this sleep/wake threshold value for Arc generated accelerometer data, when compared to PSG, sleep and wake estimates were adequate and comparable to those generated by a clinical-grade actigraph. As with other actigraphs, sleep specificity plateaus due to limitations in distinguishing wake without movement from sleep. Further studies are needed to evaluate the Arc’s ability to differentiate between sleep and wake using other sources of data available from the Arc, such as high resolution accelerometry and photoplethysmography.

A comparison of sleep, depressive symptoms, and parental perceptions between U.S. and Taiwan adolescents with self-reported sleep problems

Study Objectives

Inadequate sleep is pervasive among teens worldwide, resulting in daytime sleepiness and, in some cases, depressive symptoms. In addition to their own behavioral choices, parent perceptions may also play a role in adolescent sleep. This study conducted a preliminary evaluation of the antecedents and consequences of sleep factors among adolescents in the United States and Taiwan.

Methods

Participants were adolescents with self-reported sleep concerns from academically similar schools in Taiwan (n = 548) and northern California, United States (n = 128). Questionnaires on sleep and mood were administered to both the teens and parents.

Results

While Taiwanese students’ self-reported sleep behavior was generally better than U.S. students (p < .01), Taiwanese students had higher overall self-reported sleepiness (p < .01). Furthermore, Taiwanese parents reported teen sleep durations of 6.53 ± .827 hours per night during the week (with 45% perceiving this as sufficient), while U.S. parents reported teen sleep durations of 7.22 ± .930 hours (with 27% perceiving this as sufficient). Adolescents in both cohorts had high levels of symptoms consistent with depression (Taiwan: 70%, United States: 62%), which was associated with shorter sleep times for both cohorts and evening chronotype in the Taiwanese, but not U.S., adolescents.

Conclusions

Some differences exist between Taiwanese and U.S. adolescents, with generally better sleep and less sleepiness reported among students in the United States, and Taiwanese students’ sleep influenced more strongly by chronotype. Furthermore, Taiwanese parents reported less concern about their child’s insufficient sleep, despite the fact that inadequate sleep is strongly associated with depressive symptoms for both cohorts.

Effect of Suvorexant vs Placebo on Total Daytime Sleep Hours in Shift Workers: A Randomized Clinical Trial

IMPORTANCE

Many shift workers have difficulty sleeping during the daytime owing to an inappropriately timed circadian drive for wakefulness.

OBJECTIVE

To determine whether a dual hypocretin receptor antagonist would enable shift workers to have more daytime sleep.

DESIGN, SETTING, AND PARTICIPANTS

This double-blind, placebo-controlled randomized clinical trial included 2 weeks of baseline data and 3 weeks of intervention data, from March 2016 to December 2018. Individuals were recruited through poster advertisements in the broader San Francisco Bay area in California. From an initial voluntary recruitment cohort of 38 shift workers, 19 individuals with self-reported difficulty sleeping during the daytime following night work shift were included. Data were analyzed from Janaury to March 2019.

INTERVENTIONS

1 week of 10 mg suvorexant or placebo, titrated upward to 20 mg suvorexant or placebo for 2 additional weeks.

MAIN OUTCOMES AND MEASURES

Objective (ie, actigraphy) and subjective (ie, sleep logs) measures of sleep.

RESULTS

Among 19 participants who completed the study (mean [SD] age, 37.7 [11.1] years; 13 [68%] men), 8 participants (42%) were assigned to the suvorexant group and 11 participants (58%) were assigned to the placebo group. Compared with individuals in the placebo group, individuals in the suvorexant group increased their objective total sleep time by a mean (SE) of 1.04 (0.53) hours (P = .05) at the end of 1 week of 10-mg doses and by 2.16 (0.75) hours (P = .004) by the end of the 2 weeks of 20-mg doses. Subjective sleep was similarly improved as, compared with the placebo group, individuals in the suvorexant group increased their subjective total sleep time by a mean (SE) of 2.08 (0.47) hours (P < .001) at the end of 1 week of 10-mg doses and by 2.97 (0.56) hours (P < .001) by the end of the 2 weeks of 20-mg doses. Physician ratings of daytime sleep aligned with these measures, as there was no change in the placebo group and a much improved change in the suvorexant group. No adverse events were reported in the suvorexant group.

CONCLUSIONS AND RELEVANCE

This pilot study found that the use of a dual hypocretin receptor antagonist in shift workers under real-world conditions resulted in more than 2 extra hours of daytime sleep per episode. Future research should confirm this pilot finding in a larger sample size and examine whether, over the long term, use of this medication has a concomitant improvement in medical and psychiatric health as well as workplace performance and safety.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02491788.

0781 Impact Of Suvorexant On Total Daytime Sleep Hours In Shift Workers: A Randomized, Double-blind, Placebo-controlled Clinical Field Trial

Introduction

Many shift workers have an inability to sleep during the daytime following a night shift not due to insomnia or lack of sleep pressure, but because a circadian signal promoting wakefulness is hampering their ability to maintain sleep. We have previously hypothesized that the neuropeptide hypocretin-1 is, in part, responsible for the physiologic expression of this circadian wake signal. As such, it was our intent to determine whether a pharmacologic blockade of hypocretin would enable shift workers to obtain more daytime sleep.

Methods

Nineteen shift workers took part in a placebo-controlled, double-blind field study of suvorexant. Following two weeks of baseline, participants received 10 mg suvorexant/placebo for one week and were titrated upward to 20 mg suvorexant/placebo for an additional two weeks. Subjective (diaries) and objective (actigraphy) sleep were monitored throughout. No restrictions were placed on participants’ schedules.

Results

Both subjective and objective measures of total sleep time significantly improved in the active vs. the placebo condition, increasing by 2.08 ± 0.47 hours (diary) or 1.04 ± 0.53 hours (actigraphy) by the end of the 10 mg condition, and increasing by 2.97 ± 0.56 hours (diary) or 2.16 ± 0.75 hours (actigraphy) by the end of the 20 mg condition. Physician ratings of change in the severity of symptoms similarly improved in the active group. There were no adverse events reported in the active condition.

Conclusion

Robust changes in total sleep time were observed after administration of suvorexant, a dual-hypocretin antagonist, prior to daytime sleep in a field study of shift workers. The very large changes in total sleep time, coupled with the permissive nature of the therapeutic mechanism (i.e., suppressing wake rather than inducing sleep) indicate that this could be a viable and important therapy for shift workers.

Support

Merck Sharpe and Dohme investigator-initiated study #53236

Evening salivary cortisol as a single stress marker in women with metastatic breast cancer

BACKGROUND

Flattened diurnal salivary cortisol patterns predict shorter subsequent survival with breast, lung, and renal cell carcinomas. The underlying cause of this flattened slope is undetermined, though it has been hypothesized to be secondary to a deficit in the amplitude of the circadian clock. To gain greater insight into the portions of the diurnal salivary curve that are associated with cancer survival, we examined (1) which points in the diurnal curve are predictive of the slope of the curve and (2) whether elevated evening cortisol levels alone are associated with reduced HPA-axis feedback inhibition (i.e., decreased sensitivity to the dexamethasone suppression test).

METHOD

We examined study hypotheses on adult women with advanced breast cancer (age = 54.3 ± 9.58 years; n = 99) using non-parametric Wilcoxon's rank-sum tests, Spearman correlation coefficients and an accuracy formula based on a confusion matrix. Cortisol was sampled five times per day for three consecutive days, with dexamethasone administered late on the second day.

RESULTS

Salivary cortisol concentrations did not vary between those with flat and steep slopes during the morning (p's > .05), but did vary in the evening (p's < 0.05). Furthermore, the concentration of the 2100h alone was 86% accurate in discriminating between individuals classified as having "flat" or "steep" slopes. Dexamethasone suppression was only associated with diurnal salivary cortisol slope (p = .0042).

CONCLUSIONS

Evening cortisol levels are a sensitive indicator flattened diurnal cortisol slope, suggesting evening cortisol may also be a useful predictor of breast cancer survival. Future research should focus on determining the causes of abnormally increased evening cortisol.

Subjective sleep quality is poorly associated with actigraphy and heart rate measures in community-dwelling older men

OBJECTIVES

There has been a proliferation in the use of commercially-available accelerometry- and heart rate-based wearable devices to monitor sleep. While the underlying technology is reasonable at detecting sleep quantity, the ability of these devices to predict subjective sleep quality is currently unknown. We tested whether the fundamental signals from such devices are useful in determining subjective sleep quality.

METHODS

Older, community-dwelling men (76.5 ± 5.77 years) enrolled in the Osteoporotic Fractures in Men Study (MrOS) participated in an overnight sleep study during which sleep was monitored with actigraphy (wrist-worn accelerometry) and polysomnography (PSG), including electrocardiography (N = 1141). Subjective sleep quality was determined the next morning using 5-point Likert-type scales of sleep depth and restfulness. Lasso and random forest regression models analyzed the relationship between actigraph-determined sleep variables, the shape of the activity patterns during sleep (functional principal component analysis), average heart rate, heart rate variability (HRV), demographics, and self-reported depression, anxiety, habitual sleep, and daytime sleepiness measures.

RESULTS

Actigraphy data, in combination with heart rate, HRV, demographic, and psychological variables, do not predict well subjective sleep quality (R² = 0.025 to 0.162).

CONCLUSIONS

Findings are consistent with previous studies that objective sleep measures are not well correlated with subjective sleep quality. Developing validated biomarkers of subjective sleep quality could improve both existing and novel treatment modalities and advance sleep medicine towards precision healthcare standards.

Estimating Representative Group Intrinsic Circadian Period from Illuminance-Response Curve Data

The human circadian pacemaker entrains to the 24-h day, but interindividual differences in properties of the pacemaker, such as intrinsic period, affect chronotype and mediate responses to challenges to the circadian system, such as shift work and jet lag, and the efficacy of therapeutic interventions such as light therapy. Robust characterization of circadian properties requires desynchronization of the circadian system from the rest-activity cycle, and these forced desynchrony protocols are very time and resource intensive. However, circadian protocols designed to derive the relationship between light intensity and phase shift, which is inherently affected by intrinsic period, may be applied more broadly. To exploit this relationship, we applied a mathematical model of the human circadian pacemaker with a Markov-Chain Monte Carlo parameter estimation algorithm to estimate the representative group intrinsic period for a group of participants using their collective illuminance-response curve data. We first validated this methodology using simulated illuminance-response curve data in which the intrinsic period was known. Over a physiological range of intrinsic periods, this method accurately estimated the representative intrinsic period of the group. We also applied the method to previously published experimental data describing the illuminance-response curve for a group of healthy adult participants. We estimated the study participants' representative group intrinsic period to be 24.26 and 24.27 h using uniform and normal priors, respectively, consistent with estimates of the average intrinsic period of healthy adults determined using forced desynchrony protocols. Our results establish an approach to estimate a population's representative intrinsic period from illuminance-response curve data, thereby facilitating the characterization of intrinsic period across a broader range of participant populations than could be studied using forced desynchrony protocols. Future applications of this approach may improve the understanding of demographic differences in the intrinsic circadian period.

Effect of Light Flashes vs Sham Therapy During Sleep With Adjunct Cognitive Behavioral Therapy on Sleep Quality Among Adolescents: A Randomized Clinical Trial

IMPORTANCE

Owing to biological, behavioral, and societal factors, sleep duration in teenagers is often severely truncated, leading to pervasive sleep deprivation.

OBJECTIVE

To determine whether a novel intervention, using both light exposure during sleep and cognitive behavioral therapy (CBT), would increase total sleep time in teenagers by enabling them to go to sleep earlier than usual.

DESIGN, SETTING, AND PARTICIPANTS

This double-blind, placebo-controlled, randomized clinical trial, conducted between November 1, 2013, and May 31, 2016, among 102 adolescents enrolled full-time in grades 9 to 12, who expressed difficulty going to bed earlier and waking up early enough, was composed of 2 phases. In phase 1, participants were assigned to receive either 3 weeks of light or sham therapy and were asked to try to go to sleep earlier. In phase 2, participants received 4 brief CBT sessions in addition to a modified light or sham therapy. All analyses were performed on an intent-to-treat basis.

INTERVENTIONS

Light therapy consisted of receiving a 3-millisecond light flash every 20 seconds during the final 3 hours of sleep (phase 1) or final 2 hours of sleep (phase 2). Sham therapy used an identical device, but delivered 1 minute of light pulses (appearing in 20-second intervals, for a total of 3 pulses) per hour during the final 3 hours of sleep (phase 1) or 2 hours of sleep (phase 2). Light therapy occurred every night during the 4-week intervention. Cognitive behavioral therapy consisted of four 50-minute in-person sessions once per week.

MAIN OUTCOMES AND MEASURES

Primary outcome measures included diary-based sleep times, momentary ratings of evening sleepiness, and subjective measures of sleepiness and sleep quality.

RESULTS

Among the 102 participants (54 female [52.9%]; mean [SD] age, 15.6 [1.1] years), 72 were enrolled in phase 1 and 30 were enrolled in phase 2. Mixed-effects models revealed that light therapy alone was inadequate in changing the timing of sleep. However, compared with sham therapy plus CBT alone, light therapy plus CBT significantly moved sleep onset a mean (SD) of 50.1 (27.5) minutes earlier and increased nightly total sleep time by a mean (SD) of 43.3 (35.0) minutes. Light therapy plus CBT also resulted in a 7-fold greater increase in bedtime compliance than that observed among participants receiving sham plus CBT (mean [SD], 2.21 [3.91] vs 0.29 [0.76]), as well as a mean 0.55-point increase in subjective evening sleepiness as compared with a mean 0.48-point decrease in participants receiving sham plus CBT as measured on a 7-point sleepiness scale.

CONCLUSIONS AND RELEVANCE

This study found that light exposure during sleep, in combination with a brief, motivation-focused CBT intervention, was able to consistently move bedtimes earlier and increase total sleep time in teenagers. This type of passive light intervention in teenagers may lead to novel therapeutic applications.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT01406691.

Optimization of circadian responses with shorter and shorter millisecond flashes

Recent work suggests that the circadian pacemaker responds optimally to millisecond flashes of light, not continuous light exposure as has been historically believed. It is unclear whether these responses are influenced by the physical characteristics of the pulsing. In the present study, Drosophila (n = 2199) were stimulated with 8, 16 or 120 ms flashes. For each duration, the energy content of the exposure was systematically varied by changing the pulse irradiance and the number of stimuli delivered over a fixed 15 min administration window (64 protocols surveyed in all). Results showed that per microjoule invested, 8 ms flashes were more effective at resetting the circadian activity rhythm than 16- and 120 ms flashes (i.e. left shift of the dose-response curve, as well as a higher estimated maximal response). These data suggest that the circadian pacemaker's photosensitivity declines within milliseconds of light contact. Further introduction of light beyond a floor of (at least) 8 ms leads to diminishing returns on phase-shifting.

Auditory psychomotor vigilance testing in older and young adults: a revised threshold setting procedure

BACKGROUND

One of the most common ways to examine the daytime impact of sleep loss is the use of the psychomotor vigilance test (PVT). PVT metrics, including median reaction time (RT) and number of lapses, have been examined in a variety of studies in which both acute and chronic sleep times are manipulated. Most of these studies involve young, healthy individuals and use a visual stimulus. As light is a possible countermeasure to sleep loss, and sometimes incompatible with the use of visual PVT, PVT with auditory cues (aPVT) has been used. A threshold of 400 ms is commonly used to delineate lapses from normal RT in the aPVT. As aging can influence a variety of brain functions, we wanted to examine whether this lapse threshold was accurate for use in older adults.

METHODS

Twenty-eight young and 19 healthy older participants performed a 10-min auditory PVT approximately 90 min before habitual bedtime. The occurrence of lapses was determined by five objective RT thresholds: (1) 400 ms, (2) 500 ms, (3) 2 × median, (4) mean + 2 × SD, and (5) method 4 without outliers. Results of these methods were compared with a triplicate visual inspection of RT histograms to determine RT outside of the expected log normal distribution.

RESULTS

In both groups, methods 1, 4, and 5 performed poorly, while methods 2 and 3 were adequate, though method 3 was statistically superior.

CONCLUSION

In both age groups, the use of twice the median as an objective threshold had the best concurrence with visual scoring.

Daily Patterns of Accelerometer Activity Predict Changes in Sleep, Cognition, and Mortality in Older Men

Background

There is growing interest in the area of "wearable tech" and its relationship to health. A common element of many of these devices is a triaxial accelerometer that can yield continuous information on gross motor activity levels; how such data might predict changes in health is less clear.

Methods

We examined accelerometry data from 2,976 older men who were part of the Osteoporotic Fractures in Men (MrOS) study. Using a shape-naive technique, functional principal component analysis, we examined the patterns of motor activity over the course of 4-7 days and determined whether these patterns were associated with changes in polysomnographic-determined sleep and cognitive function (Trail Making Test-Part B [Trails B], Modified Mini-Mental State Examination [3MS]), as well as mortality over 6.5-8 years of follow-up.

Results

In comparing baseline to 6.5 years later, multivariate modeling indicated that low daytime activity at baseline was associated with worsening of sleep efficiency (p < .05), more wake after sleep onset (p < .05), and a decrease in cognition (Trails B; p < .001), as well as a 1.6-fold higher rate of all-cause mortality (hazard ratio = 1.64 [1.34-2.00]). Earlier wake and bed times were associated with a decrease in cognition (3MS; p < .05). Having a late afternoon peak in activity was associated with a 1.4-fold higher rate of all-cause mortality (hazard ratio = 1.46 [1.21-1.77]). Those having a longer duration of their daytime activity with a bimodal activity pattern also had over a 1.4-fold higher rate of cardiovascular-related mortality (hazard ratio = 1.42 [1.02-1.98]).

Conclusions

Patterns of daily activity may be useful as predictive biomarkers for changes in clinically relevant outcomes, including mortality and changes in sleep and cognition in older men.

The impact of chronotype on prosocial behavior

Introduction

Chronotype (morningness/eveningness) is associated with preference for the timing of many types of behavior, most notably sleep. Chronotype is also associated with differences in the timing of various physiologic events as well as aspects of personality. One aspect linked to personality, prosocial behavior, has not been studied before in the context of chronotype. There are many variables contributing to who, when, and why one human might help another and some of these factors appear fixed, while some change over time or with the environment. It was our intent to examine prosocial behavior in the context of chronotype and environment.

Methods

Randomly selected adults (N = 100, ages 18–72) were approached in a public space and asked to participate in a study. If the participants consented (n = 81), they completed the reduced Morning-Eveningness Questionnaire and the Stanford Sleepiness Scale, then prosocial behavior was assessed.

Results/Conclusions

We found that people exhibited greater prosocial behavior when they were studied further from their preferred time of day. This did not appear to be associated with subjective sleepiness or other environmental variables, such as ambient illumination. This suggests the importance of appreciating the differentiation between the same individual’s prosocial behavior at different times of day. Future studies should aim at replicating this result in larger samples and across other measures of prosocial behavior.

Daytime midpoint as a digital biomarker for chronotype in bipolar disorder

BACKGROUND

Bipolar disorder (BD) is associated with later sleep and daily activity (evening rather than morning chronotype). Objective chronotype identification (e.g., based on actigraphs/smartphones) has potential utility, but to date, chronotype has mostly been assessed by questionnaires. Given the ubiquity of accelerometer-based devices (e.g. actigraphs/smartphones) worn/used during daytime and tendency to recharge rather than wear at night, we assessed chronotype using daytime (rather than sleep) interval midpoints.

METHODS

Sixty-one participants with BD type I (BD-I) or II (BD-II) and 61 healthy controls completed 25-50 days of continuous actigraphy. The Composite Scale of Morningness (CSM) was completed by a subset of this group. Daytime activity midpoint was calculated for each daytime interval, excluding naps. Evening chronotype was defined as having a daytime interval midpoint at or after 16:15:00 (4:15:00 PM).

RESULTS

BD versus controls had delayed daytime midpoint (mean ± standard deviation) (16:49:07 ± 01:26:19 versus 16:12:51 ± 01:02:14, p < 0.01), and greater midpoint variability (73.3 ± 33.9 min versus 58.1 ± 18.3 min, p < 0.01). Stratifying by gender and age, females and adolescents with BD had delayed and more variable daytime midpoints versus controls. Adults with BD had greater midpoint variability than controls. Within-person mean and standard deviations of daytime midpoints were highly correlated with sleep midpoints (r = 0.99, p < 0.01 and r = 0.86, p < 0.01, respectively). Daytime midpoint mean was also significantly correlated with the CSM (r = -0.56, p < 0.01).

LIMITATIONS

Small sample size; analyses not fully accounting for daytime napping.

CONCLUSIONS

Wrist actigraphy for determination of daytime midpoints is a potential tool to identify objective chronotype. Exploration of the use of consumer devices (wearables/smartphones) is needed.