Susy P. Saraiva

Sleep disturbances and mood changes are common during the climacteric, often linked to hormonal fluctuations caused by reduced ovarian function. Evidence suggests that long‐term melatonin administration may improve the quality of life in climacteric women. This study aimed to evaluate the effects of exogenous melatonin on climacteric symptoms, sleep quality, and reproductive hormones in women working fixed shifts. A randomized clinical trial was conducted with 46 nurses working fixed shifts at a hospital in São Paulo: morning (7:00–13:00, n = 16; intervention = 7, placebo = 9), afternoon (13:00–19:00, n = 15; intervention = 8, placebo = 7), and night (19:00–7:00, n = 15; intervention = 7, placebo = 8). Participants were randomly assigned to receive either 0.3 mg of melatonin or placebo. For night shift workers, melatonin was administered only on nights off, when they were sleeping at home; the same procedure was applied to morning and afternoon workers. Data collection included sociodemographic information, self‐reported sleep quality, and menopausal symptoms. Blood samples were collected at home to measure luteinizing hormone (LH), follicle‐stimulating hormone (FSH), estradiol, and progesterone before and after the intervention. A significant main effect of melatonin was observed, with a 15.8% reduction in climacteric symptoms compared with placebo ( p = 0.01), independent of age or sleep duration, while no significant interaction with work shift was detected. Sleep quality improved by 35.33% on days off in the intervention group ( p < 0.001), with morning shift workers showing a 32.46% improvement ( p < 0.05). No significant changes were observed in reproductive hormone levels or total sleep duration. Exogenous melatonin effectively alleviates climacteric symptoms and improves sleep quality on days off, particularly among day‐shift workers, without affecting reproductive hormone concentrations or total sleep duration. Trial Registration: RBR‐10whktxm (UTN: U1111‐1305‐6221). Registered on 13 August 2025, retrospectively registered.

Poor sleep quality is associated with unhealthy dietary choices and worse body composition among night-shift workers and women during the climacteric period. This study aimed to evaluate the effect of exogenous melatonin administration on the dietary intake and body composition in healthcare workers exposed to fixed-shift work during the climacteric period. A phase II randomized, double-blind, placebo-controlled clinical trial of climacteric women working fixed morning, afternoon, or night shifts was conducted. Baseline data collection included sociodemographic information, sleep parameters, dietary intake, and body composition using bioelectrical impedance. Participants received either 0.3 mg of melatonin or a placebo for three months. Baseline total caloric and carbohydrate intake was higher among night-shift workers than afternoon-shift workers, though afternoon-shift workers a had higher body weight and fat percentage. Post-intervention, caloric intake differences dissipated due to reduced intake among night-shift workers and increased intake among afternoon-shift workers, independent of melatonin or placebo administration. However, differences in body composition persisted. Postmenopausal participants showed reduced fat mass, while premenopausal participants experienced an increase, regardless of intervention. The results suggest that physiological nighttime melatonin doses, administered on non-consecutive nights for three months, were ineffective for changing dietary intake or body composition.

Circadian hygiene, a concept not to be confused with the notion of public or social hygiene, should be discussed among experts and society. Light–dark cycles and other possible synchronizers of the human circadian timing system affect ways of life, including sleeping, eating, working and physical activity. Some of these behaviors have also been investigated individually as synchronizers (e.g., eating times). Therefore, the knowledge held today about circadian rhythms, and their implications for health, allows future perspectives in this field to be mapped. The present article summarizes the latest knowledge on factors influencing circadian rhythms to discuss a perspective for the future of health promotion based on circadian hygiene. However, it is important to highlight that circadian hygiene is the product of an imbrication of individual and societal involvement. First, it is important to adopt practices and devise public health policies in line with circadian hygiene. Second, individual healthy habits require internal rhythms to be examined. Last, the research agenda on circadian hygiene can be developed on a public as well as individual level, raising the question as to how much society is willing to embrace this change.