Sleep, Hormones, and Circadian Rhythms throughout the Menstrual Cycle in Healthy Women and Women with Premenstrual Dysphoric Disorder

A relationship exists between the sleep-wake cycle and hormone secretion, which, in women, is further modulated by the menstrual cycle. This interaction can influence sleep across the menstrual cycle in healthy women and in women with premenstrual dysphoric disorder (PMDD), who experience specific alterations of circadian rhythms during their symptomatic luteal phase along with sleep disturbances during this time. This review will address the variation of sleep at different menstrual phases in healthy and PMDD women, as well as changes in circadian rhythms, with an emphasis on their relationship with female sex hormones. It will conclude with a brief discussion on nonpharmacological treatments of PMDD which use chronotherapeutic methods to realign circadian rhythms as a means of improving sleep and mood in these women

L’exposition contrôlée à la lumière et à l’obscurité ajuste le rythme du cortisol salivaire chez les travailleurs de nuit

Dans cette étude réalisée sur le terrain et en laboratoire, nous avons testé l’efficacité d’une intervention consistant à contrôler l’exposition à la lumière/obscurité de façon à favoriser l’adaptation circadienne au travail de nuit. Six travailleurs permanents de nuit (moyenne d’âge 37,1 ± σ : 8,1 ans) avaient comme consigne de s’exposer de façon intermittente à une lumière blanche vive plein spectre (~2 000 lux) au cours des 6 premières heures de leur quart de travail de 8 heures. Il leur était demandé de se protéger de la lumière solaire du matin avec des verres teintés (densité gris neutre, transmission visuelle de la lumière 15 %) et de maintenir des épisodes réguliers de sommeil/obscurité dans une pièce très sombre. Ces épisodes devaient commencer 2 heures après la fin de chaque quart de travail de nuit. Cinq travailleurs du groupe contrôle (41,1 ± σ : 9,9 ans) ont été étudiés alors qu’ils devaient uniquement maintenir un horaire régulier de sommeil/obscurité. Des procédures de routine constante, réalisées avant et après une série d’environ 12 quarts de travail de nuit s’échelonnant sur 3 semaines, ont montré chez les travailleurs du groupe traitement une variation significative dans l’heure d’apparition du pic de cortisol ainsi qu’un ajustement de ce rythme à un horaire de travail de nuit. Un plus petit changement de phase a été observé dans le groupe contrôle, ce qui suggère une adaptation partielle à l’horaire de travail de nuit. Nos résultats démontrent l’efficacité d’une exposition judicieuse à la lumière et à l’obscurité pour favoriser l’adaptation des rythmes physiologiques au travail de nuit.The efficacy of a light/darkness intervention designed to promote circadian adaptation to night shift work was tested in this combined field and laboratory study. Six permanent night shift workers (mean age : 37.1 / s : 8.1 years) were instructed to expose themselves intermittently to full-spectrum bright white light (~2,000 lux) in the first 6 hours of their 8-hour shift. They were asked to shield themselves from morning sunlight with tinted lenses (neutral grey density, 15 % visual light transmission), and to maintain regular sleep/darkness episodes in darkened quarters beginning 2 hours after the end of each night shift. Five control group workers (41.1 / s : 9.9 years) were observed in the presence of a regular sleep/darkness schedule only. Constant routines performed before and after a sequence of ~12 night shifts over 3 weeks revealed that treatment group workers displayed significant shifts in the time of peak cortisol expression and a realignment of the rhythm with the night-oriented schedule. Smaller phase shifts suggesting an incomplete adaptation to the shift work schedule were observed in the control group. Our observations support a careful control of the pattern of light and darkness exposure for the adaptation of physiological rhythms to night shift work.En este estudio realizado en el campo y en laboratorio, hemos probado la eficacia de una intervención que consiste en controlar la exposición a la luz/oscuridad con el fín de facilitar la adaptación circadiana al trabajo de noche. Se ha dado instrucciones a seis trabajadores nocturnos permanentes (edad media 37,1 ± σ : 8,1 años) de exponerse de manera intermitente a una luz blanca viva pleno espectro (~2 000 lux) durante las seis primeras horas de su turno de trabajo de 8 horas. Se les pidió protegerse de la luz de la mañana con cristales tintados (densidad gris neutro, transmisión visual de la luz 15 %) y de mantener momentos regulares de sueño/oscuridad en un cuarto muy oscuro. Estos episodios debían empezar 2 horas después del final de cada turno de trabajo nocturno. Se ha estudiado cinco trabajadores del grupo control (41,1 ± σ : 9,9 años) que sólo debían mantener un horario regular de sueño/oscuridad. Procedimientos de rutina constante realizados antes y después una serie de más o menos 12 turnos de trabajo nocturno durante 3 semanas han demostrado con los trabajadores del grupo tratamiento una variación significativa en la hora de aparición del pico de cortisol así como un ajuste de este ritmo a un horario de trabajo nocturno. Se ha observado un cambio más pequeño de fase en el grupo control, lo que sugiere una adaptación parcial al horario de trabajo nocturno. Nuestros resultados demuestran la eficacia de una exposición adecuada a la luz y a la oscuridad para favorizar la adaptación de los ritmos fisiológicos al trabajo de noche

Prospectives

Tiré de: Prospectives, vol. 20, no 3, oct. 1984.Titre de l'écran-titre (visionné le 24 janv. 2013

Guiding principles for determining work shift duration and addressing the effects of work shift duration on performance, safety, and health

The article of record as published may be found at http://dx.doi.org/10.1093/sleep/zsab161Risks associated with fatigue that accumulates during work shifts have historically been managed through working time arrangements that specify fixed maximum durations of work shifts and minimum durations of time off. By themselves, such arrangements are not sufficient to curb risks to performance, safety, and health caused by misalignment between work schedules and the biological regulation of waking alertness and sleep. Science-based approaches for determining shift duration and mitigating associated risks, while addressing operational needs, require: 1) a recognition of the factors contributing to fatigue and fatigue-related risks; 2) an understanding of evidence-based countermeasures that may reduce fatigue and/or fatigue-related risks; and 3) an informed approach to selecting workplace-specific strategies for managing work hours. We propose a series of guiding principles to assist stakeholders with designing a shift duration decision-making process that effectively balances the need to meet operational demands with the need to manage fatigue-related risks.Academy of Sleep Medicine (AASM)Sleep Research Societ

Amplitude Reduction and Phase Shifts of Melatonin, Cortisol and Other Circadian Rhythms after a Gradual Advance of Sleep and Light Exposure in Humans

Background: The phase and amplitude of rhythms in physiology and behavior are generated by circadian oscillators and entrained to the 24-h day by exposure to the light-dark cycle and feedback from the sleep-wake cycle. The extent to which the phase and amplitude of multiple rhythms are similarly affected during altered timing of light exposure and the sleepwake cycle has not been fully characterized. Methodology/Principal Findings: We assessed the phase and amplitude of the rhythms of melatonin, core body temperature, cortisol, alertness, performance and sleep after a perturbation of entrainment by a gradual advance of the sleep-wake schedule (10 h in 5 days) and associated light-dark cycle in 14 healthy men. The light-dark cycle consisted either of moderate intensity ‘room ’ light (,90–150 lux) or moderate light supplemented with bright light (,10,000 lux) for 5 to 8 hours following sleep. After the advance of the sleep-wake schedule in moderate light, no significant advance of the melatonin rhythm was observed whereas, after bright light supplementation the phase advance was 8.1 h (SEM 0.7 h). Individual differences in phase shifts correlated across variables. The amplitude of the melatonin rhythm assessed under constant conditions was reduced after moderate light by 54 % (17–94%) and after bright light by 52 % (range 12–84%), as compared to the amplitude at baseline in the presence of a sleep-wake cycle. Individual differences in amplitude reduction of the melatonin rhythm correlated with the amplitude of body temperature, cortisol and alertness

Effect of a Thermal Catalyst on Organosilanes Treatment to Improve Durability and Stability of Canadian Wood

The demand for exterior wood siding is stagnating in North America due in part to perceptions of low durability and the need for frequent maintenance. One way to address these concerns is to modify the wood to improve its physical properties, while maintaining its appearance. In this study, white spruce was treated with organosilanes and a combination of aluminum treatments followed by a thermal treatment to improve the dimensional stability and the wood durability. Anti-swelling efficiency (ASE), leaching and decay tests were performed on the treated Canadian wood species. The quantity of hydroxyls available after treatment was evaluated by water vapor sorption. The results showed that the treatment improved the dimensional stability up to 50%. Available hydroxyls decreased by as much as 37%. The organosilanes treatment was resistant to leaching, while the aluminum was observed to leach. Organosilanes in combination with aluminum showed brown rot resistance. The addition of aluminum to the organosilanes treatment did not have effect on dimensional stability but it had a great impact on the brown rot resistance