Effects of long-term exposure to nitrogen dioxide with cardiovascular mortality: Evidence from a nationwide cohort study.

Nitrogen dioxide (NO2) is a significant ambient pollutant whose independent health effects have not been well confirmed. Evidence on the relationship between long-term NO2 exposure and cardiovascular mortality is limited and inconsistent, particularly in developing countries where such studies are scarce. This nationwide cohort study assessed the impact of long-term NO2 exposure on cardiovascular mortality in China. Data from the China Chronic Disease and Risk Factor Surveillance (CCDRFS) program were used, including adults aged 18 years and older surveyed between 2010 and 2011, followed until December 31, 2021. Mortality data were collected through the China Disease Surveillance Point (DSP) system. Annual mean NO2 concentrations from the preceding 1-2 years were estimated using satellite-based machine learning models, and incorporated as a time-varying exposure. A time-varying Cox proportional hazards model was applied to assess the relationship between NO2 exposure and mortality from total cardiovascular disease (CVD), ischemic heart disease (IHD), and stroke. Over the study period, the national mean population-weighted NO2 exposure was 26.93 (SD: 9.36) μg/m3. In fully adjusted models, a 10 μg/m3 increase in NO2 was associated with an 8.2% higher risk of cardiovascular mortality (95% CI: 2.3-14.5%), a 24.5% higher risk of IHD (95% CI: 13.5-36.4%), and a 20.9% higher risk of ischemic stroke (95% CI: 4.4-40.0%). Stronger associations were observed among those aged ≥ 65 years and those living in northern China. These findings highlight the significant impact of long-term NO2 exposure on cardiovascular mortality, particularly from IHD and ischemic stroke, and contribute to the development of more accurate exposure-response models.