Association between prior-night sleep and next-day fatigue in older adults: a daily diary study

Background Fatigue is known as an element of frailty. Sleep problems (e.g., short sleep duration and low sleep quality) can increase fatigue, but the day-to-day relationship between sleep and fatigue has not been studied well in older adults. Using a daily diary method, this study examined the within- and between-person associations between sleep and fatigue in older adults. Methods The study recruited 56 Japanese community dwellers (age: 82–86 years; female: 37.5%). Participants responded to a daily diary questionnaire at the end of each day. Over seven days, time in bed and satisfaction were measured after waking up, whereas fatigue was assessed before going to bed. We included person-level covariates (demographic factors, and physical and mental health) and day-level covariates (time in study, and positive and negative emotions). Multilevel models were estimated to examine within- and between-person associations. Results At the within-person level, on days following short and long time in bed and days following low levels of sleep satisfaction, individuals felt higher levels of fatigue compared with usual days. At the between-person level, no statistically significant differences in fatigue were observed between individuals with long and short time in bed. Conclusions The findings suggest that prior-day sleep is associated with next-day fatigue in older adults. Long and short sleep duration and low sleep quality can lead to fatigue. Considering that sleep is a modifiable health behavior, appropriate management of sleep behavior may reduce fatigue.