Association between daily light exposure and rest-activity rhythms in schizophrenia: A cross-sectional analysis of...

Circadian rhythm disruption is common in patients with schizophrenia. This study examined the association between ambient light exposure and rest-activity rhythms among schizophrenia patients.

We conducted a cross-sectional analysis involving 225 outpatients with schizophrenia enrolled in the Light Exposure and Neurobiology in Schizophrenia (LENS) study. Participants wore actigraphs on their wrists for 7 days to monitor physical activity and light exposure. Parameters of rest-activity rhythm and the 24-h light-dark cycle were calculated using cosinor analysis and nonparametric circadian rhythm analysis.

After adjustment for relevant covariates, multivariable linear regression revealed that greater daytime illuminance (from rising time to bedtime) was significantly associated with higher midline estimating statistic of rhythm (MESOR), amplitude, and the most active continuous 10-h period (M10), an earlier acrophase and M10 onset, higher interdaily stability, and lower intradaily variability. In contrast, greater nighttime illuminance (from bedtime to rising time) was significantly associated with lower amplitude and relative amplitude, a higher least active continuous 5-h period, later acrophase and M10 onset, and lower interdaily stability. Key parameters of the 24-h light-dark cycle, including amplitude, phase, and interdaily stability, were significantly aligned with rest-activity rhythms.

These findings suggest that greater daytime light exposure is associated with more robust, phase-advanced, and stable rest-activity rhythms, whereas nighttime light exposure corresponds to more dampened, delayed, and unstable rest-activity rhythms in schizophrenia patients.