The association between ozone exposure and blood pressure in a general Chinese middle-aged and older population: a large-scale repeated-measurement study.

Background: The relationship between ozone (O₃) exposure and blood pressure (BP) remains inconclusive. Given the scarcity of Chinese epidemiological data, more research on this association is of paramount importance, particularly among middle-aged and older Chinese populations.

Methods: This study involved 10,875 participants (median age: 60.0 years) in Xiamen, China, from 2013 to 2019, with 34,939 repeated BP measurements. Air pollutant exposure data, including O₃, particulate matter, nitrogen dioxide, sulfur dioxide, and carbon monoxide were derived from China High Air Pollutants and High-resolution Air Quality Reanalysis datasets using a k-nearest neighbor algorithm. The relationship between mixed air pollutant exposure and BP was evaluated using Bayesian kernel machine regression model. The effects of daily-specific O₃ exposure on BP were assessed by distributed lag models integrated into a linear mixed-effects framework. The mediating role of total cholesterol (TC), serum total bilirubin (STB), triglyceride (TG), and low-density lipoprotein (LDL) were examined using multilevel mediation analysis with a fully adjusted model.

Results: Mixed air pollutant exposure was positively correlated with BP, with O₃ being a predominant contributor exhibiting an inverse effect. O₃ exposure had immediate effects on pulse pressure (PP), while systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) showed delayed responses, with 3-, 14-, and 8-day lags, respectively. During the study period of up to 30 days, each 10 μg/m³ increase in maximum daily 8-h average O₃ concentration was associated with reductions in SBP (β =  - 1.176 mm Hg), DBP (- 0.237 mm Hg), PP (β =  - 0.973 mm Hg), and MAP (β =  - 0.544 mm Hg). Stronger correlations were observed in the older participants (aged ≥ 65 years), overweight/obese individuals, smokers and alcohol consumers, and those with hypertension or type 2 diabetes mellitus. STB and LDL mediated these effects, while TC and TG played mitigating roles.

Conclusions: Short-term O₃ exposure is negatively associated with BP in middle-aged and older Chinese individuals. The findings provide preliminary evidence for the impact of O₃ exposure on BP regulation and underscore the urgent need to reassess public health policies in response to O₃ pollution.