# Association between long-term exposure to artificial light at night and air pollution, and cardiovascular diseases in middle-aged and older adults

## TL;DR

Long-term exposure to artificial night light and air pollution increases cardiovascular disease risk in older adults, with mental health factors playing a mediating role.

## Contribution

This study identifies synergistic effects of artificial light at night and PM2.5 on CVDs and quantifies the mediating role of depression and cognitive impairment.

## Key findings

- Annual changes in artificial light at night and PM2.5 exposure significantly increase risks of hypertension, heart disease, and stroke.
- Depressive symptoms and cognitive impairment mediate 18.7% and 12.3% of cardiovascular disease risk, respectively.
- Women and adults aged ≥75 years show heightened vulnerability to these environmental stressors.

## Abstract

This longitudinal study leveraged data from the China Health and Retirement Longitudinal Study (CHARLS, 2015 wave) which contains longitudinal data from 28 provinces across the country to examine the synergistic impacts of chronic nocturnal light and air pollution (PM2.5) exposure on cardiovascular diseases (CVDs) as well as how two neuropsychological disorders (depression and cognitive impairment) mediate that effect among middle-aged and older adults in China. Using multivariable-adjusted mixed-effects logistic regression models, we identified significant interaction effects between annual changes in artificial light at night (ΔALAN) and PM2.5 exposure on hypertension (OR = 1.32, 95% CI: 1.12–1.56, p = 0.013), heart disease (OR = 1.24, 95% CI: 1.05–1.47, p = 0.028), and stroke (OR = 1.18, 95% CI: 1.02–1.36, p = 0.042). Notably, depressive symptoms and cognitive impairment mediated 18.7% and 12.3% of the total CVD risk, respectively. Subgroup analyses revealed heightened vulnerability in women (OR 1.42 vs. men OR 1.03) and adults aged ≥75 years (1.8-fold greater than younger groups). Our findings underscore the necessity of dual interventions: (1) environmental policies targeting nighttime light reduction (e.g., dimmable LED streetlights) together with air quality improvement, and (2) community-based mental health programs aiming to mitigate neuropsychological mediators. These integrated strategies could substantially alleviate the CVD burden in aging populations exposed to urbanization-driven environmental stressors.