Distinct effects of low-intensity physical activity in the evening on sleep quality in older women: A comparison of exercise and housework

The effects of intensity, type, and time of day of physical activity on sleep are not well understood. An appropriate increase in core body temperature, due to physical activity during daytime, aids sleep in older adults. Our previous study showed that evening exercise has more positive effects on sleep quality in older adults when compared with morning exercise. However, older adults who do not exercise form a large part of the population. This study aimed to examine the distinct effects of low-intensity exercise and housework during the evening on sleep quality in older women. This randomized crossover study included 10 healthy older women aged 65–79 years. The participants engaged in low-intensity physical activity for 30 min, either aerobic exercise (70 steps per minute), housework (at the same intensity), or remained sedentary (control) 3 h before bedtime. Sleep was recorded polysomnographically, and self-reported sleep quality was assessed the next morning using the Oguri-Shirakawa-Azumi sleep inventory, Middle-Aged and Aged version (OSA-MA) questionnaire. Compared with the control trial, core body temperature was significantly elevated in participants after each activity trial (0.5 ± 0.4 and 0.4 ± 0.4 °C for housework and aerobic exercise, respectively). There was a significant difference in sleep latency (14.2 ± 19.1, 9.9 ± 15.6, and 4.2 ± 3.5 min for control, housework, and aerobic exercise, respectively; ANOVA P = 0.011) among the trials. The delta power density after aerobic exercise was significantly higher than that after the control trial. We observed an increase of 53% and 15% in delta power during the 1st hour of sleep as a result of aerobic exercise and housework, respectively. The total score on OSA-MA was significantly higher after aerobic exercise (91.0 ± 5.4, 88.1 ± 6.9, and 108.6 ± 5.9 points for control, housework, and exercise, respectively). Engaging in low-intensity aerobic exercise in the evening improved polysomnographic and self-reported sleep quality. Although housework increased core body temperature to the same level as that observed after aerobic exercise, self-reported sleep quality after housework was lower than that after aerobic exercise.