Women with ovulatory menstrual cycles show an increase in body temperature in the luteal phase, compared with follicular phase, particularly during the night. Several, albeit not all, studies reported higher energy expenditure in the luteal phase compared with follicular phase. Q 10 of biological reactions lies between 2.0 and 3.0, predicting a 7-12% increase in energy expenditure when body temperature rises by 1°C. In this study, temperature dependence of energy expenditure was assessed by comparing changes in sleeping energy expenditure and thermoregulation with menstrual cycle in 9 young females. Energy expenditure was measured using a metabolic chamber, in which sleep was recorded polysomnographically, and core body temperature and skin temperature were continuously monitored. Distal-to-proximal skin temperature gradient was assessed as an index of heat dissipation. In the luteal phase, a significant increase in average core body temperature (+0.27°C) and energy expenditure (+6.9%) were observed. Heat dissipation was suppressed during the first 2 hr of sleep in the luteal phase, compared with follicular phase. Rise in basal body temperature in the luteal phase was accompanied by increased energy expenditure and suppressed heat dissipation. The 6.9% increase in metabolic rate would require a Q 10 of 12.4 to be attributable solely to temperature (+0.27°C), suggesting that energy expenditure in the luteal phase is enhanced through the mechanism, dependent and independent of lutealphase rise in body temperature presumably reflects other effects of the sex hormones.

The aim of this cross‐sectional study was to investigate the influence of replacing sedentary time with time engaged in one of two levels of physical activity on sleep quality using an isotemporal substitution model. The participants were 70 community‐dwelling older Japanese adults (approximately 70% female). Physical activity types were measured using a triaxial accelerometer and categorized based on intensity as sedentary, light‐intensity, and vigorous‐intensity. The Pittsburgh Sleep Quality Index assessed subjective sleep quality. Objective sleep parameters were assessed using an actigraph. A series of multi‐linear regression models analyzed the statistical relationships. Our findings showed that replacing 30 min of sedentary activity per day with an equal period of light‐intensity physical activity significantly influenced sleep quality parameters. However, there was no significant difference in sleep quality when light‐intensity activity was replaced with vigorous‐intensity activity. Engaging in one activity type means less available time for other types of activity; habitual replacement of sedentary activity with light‐intensity physical activity might have long‐term benefits on the sleep quality of older people.

Deteriorating sleep quality and physical or mental fatigue in older adults leads to decreased quality of life and increased mortality rates. This study investigated the effects of the time-dependent intake of nicotinamide mononucleotide (NMN) on sleep quality, fatigue, and physical performance in older adults. This randomized, double-blind placebo-controlled study evaluated 108 participants divided into four groups (NMN_AM; antemeridian, NMN_PM; post meridian, Placebo_AM, Placebo_PM). NMN (250 mg) or placebo was administered once a day for 12 weeks. Sleep quality was evaluated using the Pittsburgh Sleep Quality Index. Fatigue was evaluated using the “Jikaku-sho shirabe” questionnaire. Grip strength, 5-times sit-to-stand (5-STS), timed up and go, and 5-m habitual walk were evaluated to assess the physical performance. Significant interactions were observed between 5-STS and drowsiness. 5-STS of all groups on post-intervention and drowsiness of the NMN_PM and Placebo_PM groups on mid- and post-intervention showed significant improvement compared with those in pre-intervention. The NMN_PM group demonstrated the largest effect size for 5-STS (d = 0.72) and drowsiness (d = 0.64). Overall, NMN intake in the afternoon effectively improved lower limb function and reduced drowsiness in older adults. These findings suggest the potential of NMN in preventing loss of physical performance and improving fatigue in older adults.