Long-term exposure to low-level ozone and the risk of hypertension: A prospective cohort study conducted in a low-pollution region of southwestern China.

Background: The current evidence regarding the association between long-term exposure to ozone (O ₃ ) and hypertension incidence is limited and inconclusive, particularly at low O ₃ concentrations. Therefore, our research aims to investigate the potential link between long-term O ₃ exposure and hypertension in a region with low pollution levels.
Methods: From 2010 to 2012, we conducted a cohort prospective study by recruiting nearly 10,000 attendees through multistage cluster random sampling in Guizhou Province, China. These individuals were followed up from 2016 to 2020, and 5563 cases were finally included in the analysis. We employed a high-resolution model with both temporal and spatial accuracy to estimate the maximum daily 8-h average O ₃ and utilized annual average O ₃ concentrations for three exposure periods (2009_10, 2007_10, 2005_10) as the exposure indicator. Time-dependent covariates Cox regression model was exerted to estimate the hazard ratios (HRs) of hypertension incidence. Generalized linear model was employed to assess the association between O ₃ and systolic, diastolic, pulse, and mean arterial pressure. The dose-response curve was explored using a restricted cubic spline function.
Results: 1213 hypertension incidents occurred during 39,001.80 person-years, with an incidence density of 31.10/1000 Person Years (PYs). The average O ₃ concentrations during the three exposure periods were 66.76 μg/m ³ , 67.85 μg/m ³ , and 67.21 μg/m ³ , respectively. Per 1 μg/m ³ increase in O ₃ exposure was associated with 11 % increase in the incidence of hypertension in the single-pollution model, and the association was more pronounced in Han, urban, and higher altitude areas. SBP, PP, and MAP were increased by 0.619 (95 % CI, 0.361-0.877) mm Hg, 0.477 (95 % CI, 0.275-0.679) mm Hg, 0.301 (95 % CI, 0.127-0.475) mm Hg, respectively. Furthermore, we observed a nonlinear exposure-response relationship between O ₃ and hypertension incidence.
Conclusions: Long-term exposure to low-level O ₃ exposure is associated with an increased risk of hypertension.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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