Daily associations between outdoor air pollution and sleep quality

Background: Growing evidence links ambient air pollution, including fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3), to adverse effects on sleep. However, most prior research has relied on chronic exposure metrics and subjective sleep assessments, obscuring short-term dynamics and limiting physiological precision. To address these gaps, we examined associations of same-day and previous-day pollutant levels with both self-reported and device-measured sleep, using an ecologically valid design. Methods: Data were derived from the Budapest Sleep, Traits and Experiences Study, a 7-day observational study in which participants reported their daily activities and sleep quality ratings, and recorded EEG during sleep. Device-measured sleep outcomes included sleep efficiency, %REM sleep, sleep onset latency, and total sleep time. Daytime outdoor concentrations of PM2.5, NO2, and O3 were aggregated from monitoring stations. Linear mixed-effects models with a random intercept for participant were employed to evaluate associations between each pollutant and sleep outcome, being adjusted for age, sex, body mass index, education, weekday, season, temperature, physical activity, screen exposure, and traveling. Results: The analysis revealed that elevated O3 exposure on day 1 was associated with lower sleep efficiency and poorer perceived sleep quality on night 2. These findings survived correction for multiple comparisons, and held across multi-pollutant models and sensitivity analyses accounting for depression, insomnia, and chronotype. Notably, no robust day-to-night associations emerged for any pollutant. Conclusions: Overall, this study demonstrates a short-term relationship between outdoor ozone concentration and reduced sleep quality, even at levels deemed safe by current standards, which highlights the need for continued vigilance and regulations to protect health.