Ambient NO2 exposure hinders long-term survival of Chinese middle-aged and older adults

Serval longitudinal investigations have reported relationships between long-term nitrogen dioxide (NO2) exposure and mortality. In developing countries such as China, however, the cohort evidence was extremely rare. In this study, we aimed to establish the concentration-response relationship between long-term exposure to NO2 and mortality in Chinese adults. We conducted a prospective cohort study followed up from 2011 to 2018, by enrolling 15,440 participants aged ≥45 years from 28 provincial regions of China. NO2 concentration estimates were derived from high-quality spatiotemporal datasets developed by machine learning methods and were assigned for each participant according to their residential cities. We applied Cox proportional hazard models with time-varying exposures to assess the association of all-cause death with long-term NO2 exposure. Subgroup analyses were performed to identify effect modifications. A total of 1646 death events occurred during 105,478.5 person-years' follow-up (median 7.1 years). No evident violation for linear NO2-mortality relationship (P nonlinear = 0.332) was observed at a range of 7.4–45.0 μg/m3. Per 10-μg/m3 rise in NO2 was associated with an hazard ratio of 1.220 (95% confidence interval: 1.103–1.350) for all-cause mortality. The association between NO2 and mortality was generally robust after adjusting for co-pollutants including fine particulate matter or/and ozone. Only participants aged 65 and over (1.351 [1.193–1.531]) suffered from increased risks of death associated with NO2 exposure, and an evident effect modification by age (P = 0.008) was identified. The elevated risk of death induced by NO2 was also observed in participants living in rural areas and those with elementary school education or below, though effect modifications were non-significant in these subgroups. This study provided novel evidence that long-term NO2 exposure could be an independent risk for mortality among Chinese middle-aged and older adults. Our findings highlighted the importance of controlling air pollution induced by vehicle emissions. [Display omitted] •National study to assess association between long-term NO2 exposure and mortality in China.•No evident violation for linear relationship was found at a range of 7.4–45.0 μg/m3.•Estimated NO2-mortality association was robust to additional adjustment of co-pollutants.•Elevated mortality risk was only identified among participants aged 65 and over.