Ambient PM2.5 and NO2 exposure and sleep chronotype in adolescents: a multi-window study in Shanghai, China

Growing evidence suggests that circadian misalignment may adversely affect adolescent health, yet environmental determinants such as air pollution remain understudied. This study aimed to investigate the associations between ambient fine particulate matter (PM2.5) and nitrogen dioxide (NO2) exposure and sleep chronotype among adolescents. A total of 14,594 students were enrolled from the 2023 Shanghai Students' Common Diseases and Health Influencing Factors Surveillance. Sleep chronotype was assessed using the Morningness-Eveningness Questionnaire 5 (MEQ-5), categorizing participants into morning (M), evening (E), or neither (N) types. Air pollution data were obtained from the China National Environmental Monitoring Centre, and exposure was averaged at 7, 30, 90, 180, and 365 days prior to the survey. Generalized linear mixed models were applied to estimate associations between air pollution exposure and chronotype categories. Of the participants, 57.0% were classified as N type, 24.3% as M type, and 18.7% as E type. In single-pollutant models, higher exposure to PM2.5 and NO2 was associated with increased odds of N or E types. In two-pollutant models, NO2 exposure was significantly associated with increased risk at 180 days (OR = 1.19, 95% CI: 1.04–1.38), 90 days (OR = 1.07, 95% CI: 1.00–1.15), and 7 days (OR = 1.16, 95% CI: 1.04–1.33). When interaction terms were included, both PM2.5 (OR = 1.39, 95% CI: 1.00–2.00) and NO2 (OR = 2.03, 95% CI: 1.10–4.06) exhibited stronger associations at the 30-day exposure window. Stratified analyses indicated that girls and junior high school students were more susceptible. Exposure to PM2.5 and NO2 was associated with a shift toward later sleep chronotypes among adolescents. Given the potential health impacts of circadian disruption, targeted public health interventions to reduce air pollution exposure—particularly among vulnerable subgroups such as girls and younger students—are warranted to promote healthy sleep patterns during adolescence.