Poor Sleep, More Stress? Bidirectional Associations Between Sleep and Stress in Younger and Older Adults’ Daily Lives

Insufficient sleep has been linked with increased daytime stress and vice versa. However, previous research had poor temporal resolution regarding daytime and evening stress, leaving open whether stress across the day is differentially associated with sleep. Additionally, age differences in associations between sleep and daily stress have rarely been considered. To analyze bidirectional associations between sleep and stress across the day, we used data from 161 younger (Mage = 23.8, SD = 3.0, 49.1% male) and 170 older adults (Mage = 63.6, SD = 5.69, 41.2% male) who completed a 21-day ambulatory assessment study. Participants wore an actigraph, reported on their sleep quality each morning, and rated their current stress levels up to eight times daily. Results from dynamic structural equation models showed that lower than usual sleep quality predicted higher stress across the first half of the day whereas shorter than usual sleep duration only predicted higher stress early in the morning and around midday. Higher than usual stress in the late evening predicted worse sleep quality and stress in the early afternoon and early evening partly predicted shorter sleep duration the following night. Younger and older adults showed similar associations between sleep and stress, suggesting that these associations generalize across adulthood. However, stress levels in this study were generally low-to-moderate and future research may consider whether stress shows a strong effect on sleep once it crosses a certain threshold. In summary, effects of sleep on subsequent stress were more consistent than those of stress on subsequent sleep.