While sleep differs in adult males and females, its variation by sex during childhood is less understood. We examined sex differences in sleep measures in children and explored the influences of selective socio-demographic and health-related factors on these associations. The cohort included 323 participants aged 6-12 years who resided predominantly in low-income urban neighborhoods. Sleep duration and maintenance efficiency were assessed using wrist actigraphy. Sleep-disordered breathing (SDB) was assessed from overnight in-home testing. Validated questionnaires assessed sleep-related impairment and sleep disturbance. Linear and logistic regression modeled associations between sex and sleep outcomes, testing for effect modification by demographics, indoor environment, and neighborhood factors. Male children had higher odds for short sleep duration (<8 hours; Odds Ratio [OR]=1.81, 95% confidence interval [CI]: 1.06, 3.08) and low sleep efficiency (< 85%; OR=2.04, 95% CI: 1.24, 3.35), which persisted after adjusting for health-related factors. Male sex was associated with a 17.4% higher geometric mean of SDB respiratory event frequency (p<0.05). Effect modification analysis showed stronger associations between male sex and lower sleep efficiency for children older than 10 years, between male sex and short sleep duration for minority children, and between male sex and SDB for children of mothers with lower education. No sex differences were observed in parent-reported sleep outcomes. Male children were at higher risk for several objectively measured but not for caregiver-reported sleep outcomes; findings were unexplained by common health problems. Risk appeared further elevated in males who were older than 10 years and were of minority ethno-racial background or from homes with low maternal education.

Flight departure and arrival times contribute to the variability of jetlag duration and can reverse the direction of circadian adaptation post-flight. These dynamics are mainly governed by light exposure and sleep timing during and around flights. Statement of Significance This study provides a quantitative analysis of how flight itineraries interact with circadian and sleep physiology to determine jetlag duration. By simulating over 55,000 flights across all time zone transitions, we reveal systematic patterns linking flight timing with adaptation time and the opportunities to minimise circadian disruption through itinerary design and behaviours during and around flights. These findings advance the mechanistic understanding of jetlag and offer actionable insights for travellers and airlines to reduce jetlag burden through optimised flight schedules and personalised strategies.

Individual sleep/wake patterns can be characterized by the intraindividual mean (iM) and variability (iSD), which captures night-to-night fluctuations. Most accelerometry-based sleep studies assess 7-14 nights, which may be insufficient for reliable variability estimates. This pre-registered, large cohort study quantifies how many nights are needed for reliable sleep iM and iSD estimates using accelerometry. Participants (n= 10 412, Mage= 37.75±10.65, 50.00% women) wore a validated, wrist-worn biometric device (WHOOP) for one year (3 700 492 person-nights). Total sleep time (TST), sleep onset, midsleep, sleep offset, wake after sleep onset (WASO), and sleep percentage were estimated. Reliability correlation coefficients compared reference values (calculated from all 363 nights) with 2-362 consecutive nights randomly selected per participant, with r> .80 considered reliable. 95% limits of agreement were calculated using the Bland-Altman method. Reliable iM estimates (r > .80) were achieved with 2-7 nights of data, depending on the sleep metric: TST (7 nights), sleep-onset and midsleep (3), sleep-offset and sleep percentage (4), WASO (5). In contrast, reliable iSD estimates required substantially more nights: TST (43 nights), sleep-onset (44), midsleep and sleep-offset (41), sleep percentage (62), and WASO (65). iSDs estimated from 7-14 nights showed poor reliability (r = .50-.67) and wide 95% limits of agreement (e.g., TST: ±50.5min for 7 nights). Findings highlight the importance of tailoring study periods to the specific sleep metric of interest. Longer monitoring periods may improve diagnostic consistency and inform evidence-based recommendations for sleep assessments in clinical and research settings.

The long-term trajectory of cognitive changes in isolated REM sleep behavior disorder (iRBD) remains unclear. Increasing evidence suggests potential heterogeneity in disease progression. People who maintained an iRBD diagnosis without phenoconversion for at least 5years were included in this study. Cognitive changes over time were assessed using linear mixed models. Subgroup analyses were conducted for men and women separately, and for people with longstanding iRBD. A total of 318 neuropsychological assessments from 162 people with iRBD (28% women) were analyzed. The mean age at diagnosis was 65.6years, with an average follow-up duration of 7.7years. Significant linear declines were observed across attention/working memory and memory domains, with notable decreases in Digit Symbol ($\beta$= -0.084, 95% confidence intervals [CI] -0.102 to -0.066), the Stroop color-naming test ($\beta$= -0.054, 95% CI -0.074 to -0.054), and Word List Recall ($\beta$= -0.054, 95% CI -0.078 to -0.030) as representative examples. In the longstanding-iRBD subgroup (n = 33) and among men, cognitive decline patterns largely mirrored those observed in the full cohort, with significant declines in attention/working memory and memory. In contrast, women exhibited a more restricted decline, limited to digit span forward ($\beta$= -0.055, 95% CI -0.102 to -0.008) and digit symbol ($\beta$= -0.082, 95% CI -0.121 to -0.043). Gradual cognitive decline in attention/working memory and memory may represent a natural course of neurodegeneration in men with iRBD, without necessarily indicating imminent phenoconversion. Women with iRBD appeared to show greater resilience to cognitive decline compared to men. Statement of Significance Cognitive impairment is common in isolated REM sleep behavior disorder (iRBD) and is considered a potential marker of phenoconversion to overt neurodegenerative disorders, such as Parkinson's disease or dementia with Lewy bodies. This study, overcoming prior limitations of short follow-up and small samples, provides long-term data demonstrating a gradual decline in attention/working memory and memory domains among people with iRBD. It also reveals sex-specific vulnerability, with men showing more pronounced decline than women, and confirms that even people with longstanding iRBD experience cognitive deterioration over time. These findings highlight the need for sex-specific approaches when monitoring cognitive progression in iRBD, and future studies should map distinct cognitive-decline trajectories to subsequent phenoconversion risk and clarify the mechanisms underlying the observed sex differences.

To investigate the associations of periodic limb movements during sleep (PLMS) and restless legs syndrome (RLS) symptoms with longitudinal changes in cognitive performance among older adults. We analyzed data from 382 community-dwelling older adults without dementia participating in the HypnoLaus study (mean age: 71.0 ± 4.1years; 42.9% male). Participants underwent polysomnography and baseline cognitive testing, followed by a second cognitive assessment after 4.7 ± 0.6years. Individuals were categorized by PLMS index (PLMI) as <15/h (reference), 15-29.9/h, and ≥30/h. Associations between PLMI categories and annualized changes in executive function (Stroop Test), verbal fluency, and verbal memory were examined using multiple linear regression models adjusted for potential confounders. Additional analyses evaluated the role of RLS symptoms and PLMI × RLS symptoms interactions. A PLMI ≥30/h was associated with a steeper deterioration in executive function compared with the reference group (B = -0.06 standard deviations [SD]/year, p = .010), equivalent to -0.3 SD and -1.5 SD declines over 5years relative to the baseline performance and to the distribution of change scores, respectively. This association was independent of RLS symptoms and other sleep-related conditions. No significant associations were observed between PLMI and changes in verbal fluency or verbal memory. RLS symptoms were not associated with changes in any cognitive outcome, and no PLMI × RLS symptoms interaction was detected. High PLMS frequency was independently associated with accelerated deterioration in executive function, suggesting a link between PLMS and cognitive aging. In contrast, RLS symptoms showed no association with changes in cognitive function. Statement of Significance This study suggests that periodic limb movements during sleep (PLMS) may be related to early cognitive vulnerability and could represent an early marker of accelerated cognitive aging. A higher frequency of PLMS was associated with a steeper deterioration in executive function over about 5years in community-dwelling older adults, independent of restless legs syndrome symptoms, other sleep conditions, and relevant clinical factors. These findings highlight the need for future research to elucidate the neurobiological mechanisms linking PLMS to accelerated cognitive aging, and to determine whether reducing PLMS could help preserve cognitive health, or whether PLMS primarily represent a marker rather than a direct contributor to cognitive deterioration.