Differential effects of fine particulate matter constituents on obstructive sleep apnea severity: A nationwide analysis of smart device-based monitoring

Abstract While ambient fine particulate matter (PM 2.5 ) is linked to obstructive sleep apnea (OSA), the specific roles of its chemical constituents have never been investigated. Using a nationwide smart device-based cohort encompassing 6,395,382 person-days of sleep monitoring from 53,297 adults at moderate-to-severe OSA risk across 313 Chinese cities, we conducted a case time series study to evaluate short-term associations between daily concentrations of PM₂.₅ constituents (organic matter, black carbon, nitrate, sulfate, and ammonium) and OSA exacerbation, apnea–hypopnea index (AHI), and oxygen saturation. All five constituents were significantly associated with adverse OSA outcomes, with organic matter and black carbon exerting the strongest effects. Each interquartile range increase in organic matter (lag 0–1 days) was associated with a 1.92% increase in OSA exacerbation risk (95% CI: 1.56–2.28), a 0.08 events/h increase in AHI (95% CI: 0.06–0.09), and a 0.008% decrease in oxygen saturation (95% CI: 0.007–0.008). Black carbon demonstrated comparably strong adverse effects across all outcomes. The remaining constituents showed weaker but directionally consistent associations, with effect estimates ranging from 1.41% to 1.45% for OSA exacerbation, around 0.06 events/h for AHI, and 0.005–0.006% for oxygen saturation. These findings provide the first evidence that specific PM 2.5 constituents contribute differentially to OSA severity, underscoring the importance of targeting carbonaceous particles in air quality management.