Nighttime light exposure is associated with metabolic dysfunction in schizophrenia: A cross-sectional analysis of the LENS study

STUDY OBJECTIVES: Accumulating evidences have investigated the impact of nighttime light exposure on metabolic dysfunction, including obesity, hypertension, diabetes, and dyslipidemia, in the general population. However, no study has investigated this effect in patients with schizophrenia. Therefore, this study aimed to investigate the association between nighttime light exposure and metabolic dysfunction in patients with schizophrenia. METHODS: This was a cross-sectional study including 222 outpatients with schizophrenia enrolled in the Light Exposure and Neurobiology in Schizophrenia (LENS) study. Nighttime light exposure was objectively evaluated using a wrist-worn actigraph and a bedside photometer over 7 consecutive days. Physical examinations and blood sampling were performed at the clinic. RESULTS: After adjusting for potential confounding factors, multivariable logistic regression analysis revealed that the participants with the highest quartile of nighttime illuminance measured using actigraphy had significantly higher odds ratios (OR) for obesity (OR, 4.01; 95% confidence interval [CI], 1.69-9.53), hypertension (OR, 3.38; 95% CI, 1.40-8.18), and dyslipidemia (OR, 2.41; 95% CI, 1.01-5.74) than those with the lowest quartile. No significant association was observed between nighttime illuminance and OR for diabetes. However, increased nighttime illuminance was significantly associated with higher glycosylated hemoglobin levels. A significant association was observed between nighttime illuminance measured using the bedside photometer and OR for hypertension. CONCLUSION: We found a significant association between nighttime light exposure and metabolic dysfunction in patients with schizophrenia. Further longitudinal studies are needed to clarify this association.