Does sunlight exposure predict next-night sleep? A daily diary study among U.S. adults.

Poor sleep is becoming increasingly prevalent and is associated with adverse health outcomes. Sunlight exposure may improve sleep by regulating circadian rhythms, increasing vitamin D, and influencing melatonin production. However, research on the sunlight-sleep association is limited, especially outside of cross-sectional designs. This study examined associations between daily self-reported sunlight exposure and next-night sleep quality in 103 adults for up to 70 days. The timing of sunlight exposure predicted next-night sleep quality. Specifically, morning sunlight exposure, relative to no sunlight, predicted better sleep quality based on responses to the brief Pittsburg Sleep Quality Index. Duration of sunlight exposure was generally not associated with sleep quality. Morning sunlight may regulate circadian rhythms, subsequently improving sleep. Findings have potential implications for sleep interventions and daylight savings time policies. Future research should test whether morning sunlight exposure can enhance the effectiveness of sleep interventions.

Examining the Longitudinal Bi-Directional Associations of Friend Engagement, Social Functioning, and Depression.

Various components of social functioning predict depression and these associations can vary by gender. Bi-directional associations may be important to consider as social factors may influence depressive symptoms while depressive symptoms may impact social factors. Most previous longitudinal research examining bi-directional effects has traditionally used the cross-lagged panel model (CLPM), which has some inherent weaknesses. This study sought to apply a more comprehensive analysis to examine bi-directional associations between friend engagement, social functioning, and depressive symptoms. Random intercept cross-lagged panel models (RI-CLPM) were tested on three waves from the Wisconsin Longitudinal Study (N = 5890). Average levels of social functioning were positively associated with friend engagement and negatively associated with depression. Fluctuations in social functioning and friend engagement were negatively associated with same-wave depressive symptoms. Lastly, depression was predicted by previous fluctuations in social functioning, although the findings varied by gender. This study showed that the relationships between social factors and depression are apparent within and across large time intervals, even while controlling for between-person associations. These findings add further support to the need to attend to social life as a predictor of depression in older adults. Future research could improve upon this research by examining the characteristics of the friendship interactions and including more diverse samples.