Association between outdoor light at night and hypertension and high-normal blood pressure: A nationwide cross-sectional study among Chinese adults

The authors aimed to investigate the association between outdoor light at night (LAN) intensity and blood pressure. The study included 13 507 participants aged 45 and above from the 2011-2012 China Health and Retirement Longitudinal Study baseline survey. Blood pressure measurements were obtained by averaging the last two readings recorded (three measurements with an interval of 45-60 s between each measurement) during the survey. Outdoor LAN intensity was assessed using Defense Meteorological Satellite Program data. The study categorized participants based on quartiles of outdoor LAN intensity and employed statistical methods like linear regression, restricted cubic splines, and logistic models to analyze the connections. After adjusting for potential confounding factors, higher levels of outdoor LAN intensity were associated with increase in systolic blood pressure (0.592 mmHg/interquartile range [IQR], 95% confidence interval [CI]: 0.027,1.157), diastolic blood pressure (0.853 mmHg/IQR, 95% CI: 0.525,1.180) and mean arterial pressure (0.766 mmHg/IQR, 95% CI: 0.385,1.147). Interestingly, the relationship between LAN intensity and odds of hypertension followed a non-linear pattern, resembling a reverse "L" shape on cubic splines. Participants with the highest quartile of outdoor LAN intensity had 1.31-fold increased odds of hypertension (95% CI: 1.08-1.58) compared to the lowest quartile. Additionally, there was an observable trend of rising odds for high-normal blood pressure with higher levels of LAN intensity in the crude model, but no statistically significant differences were observed after adjusting for confounding factors. In conclusion, this study underscores a significant connection between outdoor LAN intensity and the prevalence of hypertension.