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Abstract 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

In humans, exposure to continuous light is typically used to change the timing of the circadian clock. This study examines the efficiency of a sequence of light flashes (“flash therapy”) applied during sleep to shift the clock. Healthy participants (n = 10) took part in two 36-h laboratory stays, receiving a placebo (goggles, no light) during one visit and the intervention (goggles, 2-ms flashes broad-spectrum light for 60 min, delivered every 15 s, starting 30 min after habitual sleep onset) during the other. Circadian phase shift was assessed with changes in salivary dim light melatonin onset (DLMO). Sleep, measured with polysomnography, was analyzed to assess changes in sleep architecture and spectral power. After 1 h of flashes, DLMO showed a substantial delay (1.13 ± 1.27 h) compared to placebo (12 ± 20 min). Two individuals exhibited very large shifts of 6.4 and 3.1 h. There were no substantive differences in sleep architecture, but some evidence for greater instability in sleep. 1 h of flash therapy during sleep evokes large changes in circadian timing, up to 6 h, and does so with only minimal, if any, impact on sleep. Flash therapy may offer a practical option to delay the circadian clock in shift workers and jet travelers.

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. 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. 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. 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.

We aimed to synthesize and critically evaluate human studies on the impact of circadian and sleep factors on influenza vaccine-induced immune responses. A comprehensive literature review was conducted, and of the 1260 studies identified, 13 met the inclusion criteria for evaluating vaccination timing, circadian misalignment, and sleep parameters in relation to influenza vaccine-induced immune responses in human populations. Most studies assessed humoral immune responses, primarily antibody titers. Morning vaccination (typically between 9:00 and 11:00 AM) was associated with higher antibody titers compared to afternoon vaccination, particularly for the A/H1N1 strain in adults aged ≥ 65 years. Short sleep duration—especially in the two nights preceding vaccination—was associated with reduced antibody levels, while acute sleep deprivation the night after vaccination transiently reduced antibody levels in males. Sleep fragmentation and excessive daytime sleepiness were linked to increased vulnerability to breakthrough infections. Evidence on circadian misalignment from shift work was mixed. Clinical outcomes were reported in one large trial, where morning vaccination correlated with fewer respiratory hospitalizations. Current evidence supports a potential role for circadian timing and sleep duration in enhancing vaccine-induced antibody responses, particularly in older adults and individuals with sleep or circadian disruption. However, inconsistencies, modest effect sizes, and methodological limitations preclude broad recommendations. Future studies should incorporate direct measures of circadian phase, stratify by chronotype and population (e.g., shift workers), and evaluate both immunologic and clinical outcomes to inform targeted chrono-immunization strategies.

Study Objectives: Persons > 65 years with short sleep duration (≤ 6 hours) are at risk for adverse outcomes, but the accuracy of self-reported sleep duration may be affected by reduced symptom awareness. We evaluated the performance characteristics of self-reported vs objectively measured sleep duration in this age group. Methods: In 2,980 men from the Osteoporotic Fractures in Men Sleep Study and 2,855 women from the Study of Osteoporotic Fractures we examined the agreement and accuracy of self-reported vs actigraphy-measured short and normal (> 6 but < 9 hours) sleep duration. We evaluated associations of select factors (demographics; medical, physical, and neuropsychiatric conditions; medication and substance use; and sleep-related measures) with risk of false-negative (normal sleep duration by self-report but short sleep duration by actigraphy) and false-positive (short sleep duration by self-report and normal sleep duration by actigraphy) designations, respectively, using logistic regression. Results: Average ages were 76.3 ± 5.5 and 83.5 ± 3.7 years in men and women, respectively. There was poor agreement between self-reported and actigraphic sleep duration (kappa ≤ 0.24). False negatives occurred in nearly half and false positives in over a quarter of older persons. In multivariable models in men and women, false negatives were independently associated with obesity, daytime sleepiness, and napping, while false positives were significantly lower with obesity. Conclusions: Under- and overreporting of short sleep is common among older persons. Reliance on self-report may lead to missed opportunities to prevent adverse outcomes or unnecessary interventions. Self-reported sleep duration should be objectively confirmed when evaluating the effect of sleep duration on health outcomes. Citation: Miner B, Stone KL, Zeitzer JM, et al. Self-reported and actigraphic short sleep duration in older adults. J Clin Sleep Med . 2022;18(2):403–413.

Background Sleep-wake regulating circuits are affected during prodromal stages in the pathological progression of both Alzheimer’s disease (AD) and Parkinson’s disease (PD), and this disturbance can be measured passively using wearable devices. Our objective was to determine whether accelerometer-based measures of 24-h activity are associated with subsequent development of AD, PD, and cognitive decline. Methods This study obtained UK Biobank data from 82,829 individuals with wrist-worn accelerometer data aged 40 to 79 years with a mean (± SD) follow-up of 6.8 (± 0.9) years. Outcomes were accelerometer-derived measures of 24-h activity (derived by cosinor, nonparametric, and functional principal component methods), incident AD and PD diagnosis (obtained through hospitalization or primary care records), and prospective longitudinal cognitive testing. Results One hundred eighty-seven individuals progressed to AD and 265 to PD. Interdaily stability (a measure of regularity, hazard ratio [HR] per SD increase 1.25, 95% confidence interval [CI] 1.05–1.48), diurnal amplitude (HR 0.79, CI 0.65–0.96), mesor (mean activity; HR 0.77, CI 0.59–0.998), and activity during most active 10 h (HR 0.75, CI 0.61–0.94), were associated with risk of AD. Diurnal amplitude (HR 0.28, CI 0.23–0.34), mesor (HR 0.13, CI 0.10–0.16), activity during least active 5 h (HR 0.24, CI 0.08–0.69), and activity during most active 10 h (HR 0.20, CI 0.16–0.25) were associated with risk of PD. Several measures were additionally predictive of longitudinal cognitive test performance. Conclusions In this community-based longitudinal study, accelerometer-derived metrics were associated with elevated risk of AD, PD, and accelerated cognitive decline. These findings suggest 24-h rhythm integrity, as measured by affordable, non-invasive wearable devices, may serve as a scalable early marker of neurodegenerative disease.

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. 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. 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.

Background Emotion regulation (ER) is a key process underlying posttraumatic stress disorder (PTSD), yet, little is known about how ER changes with PTSD treatment. Understanding these effects may shed light on treatment processes. Methods We recently completed a non-inferiority design randomised controlled trial demonstrating that a breathing-based yoga practice (Sudarshan kriya yoga; SKY) was not clinically inferior to cognitive processing therapy (CPT) across symptoms of PTSD, depression, or negative affect. Here, in secondary exploratory analyses (intent-to-treat N  = 85; per protocol N  = 59), we examined whether self-reported ER (Difficulties in Emotion Regulation Scale; DERS) and physiological ER (heart rate variability; HRV) improved with treatment for clinically significant PTSD symptoms among US Veterans. Results DERS-Total and all six subscales improved with small-to-moderate effect sizes ( d  = .24–.66) following CPT or SKY, with no differences between treatment groups. Following SKY (but not CPT), HR max–min (average difference between maximum and minimum beats per minute), LF/HF (low-to-high frequency) ratio, and normalised HF-HRV (high frequency power) improved (moved towards a healthier profile; d  = .42–.55). Conclusions To our knowledge, this is the first study to demonstrate that a breathing-based yoga (SKY) improved both voluntary/intentional and automatic/physiological ER. In contrast, trauma-focused therapy (CPT) only reliably improved self-reported ER. Findings have implications for PTSD treatment and interventions for emotional disorders more broadly. Trial registration Secondary analyses of ClinicalTrials.gov NCT02366403 .

Light plays a crucial role in regulating nocturnal sleep patterns. This cross-sectional study evaluated the potential association between levels of light exposure in real-life settings and sleep parameters in individuals with bipolar disorder. We included 204 ambulatory individuals with bipolar disorder who participated in the APPLE (Association between Pathology of Bipolar Disorder and Light Exposure in Daily Life) cohort study. Daytime illuminance and sleep were assessed using actigraphy over a seven-day period. In addition, a portable light meter was used to evaluate the illuminance levels in the bedroom during nighttime. The median values of daytime illuminance and nighttime illuminance were 221.8 lux (interquartile range: 150.9–306.9 lux) and 2.3 lux (0.3–9.6 lux), respectively. Multivariable linear regression analyses, adjusting for potential confounders, revealed a significant association between greater daytime illuminance and higher sleep efficiency as well as shorter sleep onset latency and wake after sleep onset. Moreover, the interaction term of daytime and nighttime illuminance demonstrated a significant correlation with sleep efficiency (95% confidence interval [CI], −10.45 to −2.17; P  = 0.003), sleep onset latency (95% CI, 0.18 to 0.91; P  = 0.004), and wake after sleep onset (95% CI, 13.47 to 50.1; P  < 0.001). Our findings indicate the existence of a significant positive correlation between daytime light exposure and sleep parameters in individuals with bipolar disorder. The interaction of increased daytime light and decreased nighttime light appears to be positively associated with sleep quality.

Ocular light sensitivity is the primary mechanism by which the central circadian clock, located in the suprachiasmatic nucleus (SCN), remains synchronized with the external geophysical day. This process is dependent on both the intensity and timing of the light exposure. Little is known about the impact of the duration of light exposure on the synchronization process in humans. In vitro and behavioral data, however, indicate the circadian clock in rodents can respond to sequences of millisecond light flashes. In a cross-over design, we tested the capacity of humans (n = 7) to respond to a sequence of 60 2-msec pulses of moderately bright light (473 lux) given over an hour during the night. Compared to a control dark exposure, after which there was a 3.5±7.3 min circadian phase delay, the millisecond light flashes delayed the circadian clock by 45±13 min (p<0.01). These light flashes also concomitantly increased subjective and objective alertness while suppressing delta and sigma activity (p<0.05) in the electroencephalogram (EEG). Our data indicate that phase shifting of the human circadian clock and immediate alerting effects can be observed in response to brief flashes of light. These data are consistent with the hypothesis that the circadian system can temporally integrate extraordinarily brief light exposures.