Light Exposure, Physical Activity, and Sleep Duration: Evidence of Nonlinear Associations and Interactive Effects in...

This study aimed to examine the independent and interactive effects of light exposure duration and moderate-to-vigorous physical activity (MVPA) on sleep duration, and to explore the potential non-linear characteristics of these relationships. Data were drawn from the UK Biobank, including a total of 100,021 adults. Objectively measured variables of daily light exposure, physical activity, and sleep duration were extracted. After adjusting for age, sex, smoking status, alcohol drinker status, and body mass index (BMI), multiple linear regression models were used to assess their associations. Interaction terms were added to examine potential synergistic effects between light exposure and physical activity. Segmented regression analysis, implemented in Python, was used to identify non-linear breakpoints in these relationships. Light exposure was significantly negatively associated with sleep duration (unstandardized B =  -0.617, p < .001), as was MVPA time (unstandardized B =  -0.636, p < .001). However, their interaction showed a significant positive effect (unstandardized B = 0.342, p < .001). Segmented regression identified two critical thresholds in the relationship between light exposure and sleep duration, and between MVPA and sleep.Both light exposure and moderate-to-vigorous physical activity significantly influence sleep duration.