bims-ciryme 2024-11-10 papers

NPJ Biol Timing Sleep. 2024 ;1(1): 13

Melatonin's role in the timing of sleep onset is conserved in nocturnal mice.

Pureum Kim, Nicholas Garner, Annaleis Tatkovic, Rex Parsons, Prasad Chunduri, Jana Vukovic, Michael Piper, Martina Pfeffer, Marco Weiergräber, Henrik Oster, Oliver Rawashdeh.

Melatonin supplementation strengthens non-restorative sleep rhythms and its temporal alignment in both humans and night-active rodents. Of note, although the sleep cycle is reversed in day-active and night-active (nocturnal) mammals, both, produce melatonin at night under the control of the circadian clock. The effects of exogenous melatonin on sleep and sleepiness are relatively clear, but its endogenous role in sleep, particularly, in timing sleep onset (SO), remains poorly understood. We show in nocturnal mice that the increases in mid-nighttime sleep episodes, and the mid-nighttime decline in activity, are coupled to nighttime melatonin signaling. Furthermore, we show that endogenous melatonin modulates SO by reducing the threshold for wake-to-sleep transitioning. Such link between melatonin and SO timing may explain phenomena such as increased sleep propensity in circadian rhythm sleep disorders and chronic insomnia in patients with severely reduced nocturnal melatonin levels. Our findings demonstrate that melatonin's role in sleep is evolutionarily conserved, effectively challenging the argument that melatonin cannot play a major role in sleep regulation in nocturnal mammals, where the main activity phase coincides with high melatonin levels.

Keywords: Circadian rhythms and sleep; Melatonin

DOI: https://doi.org/10.1038/s44323-024-00013-1

Exp Physiol. 2024 Nov 01.

The impact of long-haul travel and 13 h time change on sleep and rest activity circadian rhythm in speed skaters during World Cup competitions.

Giorgio Varesco, Chun William Yao, Evelyne Dubé, Guido Simonelli, François Bieuzen.

Athletes frequently compete only a few days after long-haul travel. Longitudinal real-world data on athletes' sleep and sleep-wake cycle in competitive settings remain scarce. This study assessed the impact of a long-haul travel across ∼13 time zones on sleep patterns, rest-activity circadian rhythms (RAR), and their subsequent effects on neuromuscular function and race performance in the Canadian Short-Track Speed Skating Team. Nineteen athletes (24 ± 4 years, 11 women) travelled from Montréal (UTC-5) to Asia (UTC+8, UTC+9) for World Cup races between 2017 and 2019. Actigraphy data were collected before (Baseline) and during travel, during the stay in Asia (SIA), and during competition days. RAR were computed using cosinor analyses on accelerometry data with 24 h phase periods. Countermovement jump height (CMJ) was measured in a subsample (n = 10). Compared to baseline (7:08 ± 0:53), athletes obtained less sleep during travel (6:16 ± 1:27) and competition days (6:35 ± 1:10), and more during SIA (7:32 ± 0:46; time effect P < 0.0001). Sleep efficiency and CMJ were greater in SIA than baseline (P = 0.007 and P = 0.0004, respectively). During SIA, sleep time increased by 9 min per night until the fifth day (P < 0.0001), with a slight decrease in sleep efficiency (P = 0.005) and an increase in CMJ (P < 0.0001). For RAR, mean activity peaked on day 2, shifting from late evening to ∼15:00. Race performance was not different from other races of the same season (P > 0.254). Our results demonstrated that, despite the possible sleep debt from the long-haul travel, athletes recovered within 5 days, highlighting their adaptability to manage sleep debt and jetlag without impacting competitive outcomes.

Keywords: athletes sleep; jet‐lag; long‐haul travels; sport performance

DOI: https://doi.org/10.1113/EP092195

Age Ageing. 2024 Nov 01. pii: afae242. [Epub ahead of print]53(11):

Association of night shift work and biological ageing: the mediating role of body mass index.

Wenqi Shen, Lingli Cai, Jiang Li, Ying Sun, Bin Wang, Ningjian Wang, Yingli Lu.

BACKGROUND: We aimed to examine whether current and lifetime night shift work is associated with accelerated biological ageing and the potential role of body mass index (BMI) in mediating the association.
METHODS: Data were sourced from the UK Biobank cohort. This study included participants who reported detailed information on their current work schedule and had complete data to calculate PhenoAge. The outcome of interest was biological ageing, measured by PhenoAge acceleration. Multivariable linear regression models were conducted to test the relationship between night shift work and biological ageing. Mediation analyses were performed.
RESULTS: Of the 182 064 participants included, the mean age was 52.6 years, and 51.1% were male. After adjustment for chronological age and sex, compared with day workers, shift workers without night shift, irregular night shift workers and permanent night shift workers were associated with 0.59-, 0.87- and 1.30-year increase in biological ageing, respectively (P for trend <.001). Considering the lifetime work schedule, participants who worked night shifts >10 years and participants who worked >8 night shifts each month showed increased biological age acceleration [>10 years: β = 0.54, 95% confidence interval (CI) 0.29-0.79; >8 times/month: β = 0.29, 95% CI 0.07-0.50]. The mediation analysis showed that BMI mediated the associations between night shift work and biological age acceleration by 36%-53%.
CONCLUSIONS: We showed that night shift work was associated with accelerated biological ageing. Our findings highlight the interventions on appropriate shift work schedules and weight management in night shift workers, which may slow the biological ageing process and ultimately reduce the burden of age-related diseases.

Keywords: PhenoAge; biological ageing; body mass index (BMI); night shift work; older people

DOI: https://doi.org/10.1093/ageing/afae242

Sci Rep. 2024 Nov 01. 14(1): 26298

Redefining artificial lighting through spectral engineering of light sources for well-being.

O Moreno, C Fuentes-Hernandez, B Kippelen.

Light-emitting diodes (LEDs) have revolutionized artificial lighting, but also exposed the detrimental health effects that stem from insufficient exposure to natural light. Human-centric artificial lighting requires both visual quality and circadian lighting performance that mimics daylight's evolving spectral power distribution (SPD). Here, we present a color-tunable LED-based light source that achieves SPDs similar to various conditions of daylight and incandescent lighting over the range of visible wavelengths. This light source is comprised of a linear combination of light converter channels containing dyes exhibiting thermally activated delayed fluorescence (TADF) fabricated through additive manufacturing, photoexcited by violet-emitting LEDs (VLED). This hybrid light source establishes a new benchmark for state-of-the-art artificial lighting at approximating daylight, with Illuminating Engineering Society (IES) color gamut index Rg values within 3%, IES color fidelity index Rf values within 7% through CCT values ranging from 4277 K to 22,333 K. We propose efficiency metrics to accurately quantify similarity between light sources and the respective reference daylight spectrum encompassing visual and circadian effects, facilitating WLED benchmarking. The efficiency metrics pertaining to circadian lighting performance remain within 10% over the same CCT range. These results advance lighting science to address simultaneously the grand challenges of health and sustainability.

DOI: https://doi.org/10.1038/s41598-024-78315-4