Cold Waves and Elevation Strengthen the Association of Particulate Matter Exposure With Hypertension Prevalence: A Large Multiregional Study in China

Background Hypertension is a major global health burden. While air pollution is a known risk factor, the interactive effects of co‐occurring stressors like cold weather and geographic elevation are poorly understood. This study investigated the independent and joint effects of long‐term particulate matter (PM) exposure, cold waves, and elevation on hypertension. Methods We conducted a cross‐sectional study of 27 602 adults across multiple regions in China. Long‐term exposures to PM and its chemical components were estimated using 3 independent, high‐resolution data sets, alongside cumulative cold‐wave days and residential elevation. Generalized linear models and principal component analysis were used to estimate associations with hypertension prevalence and blood pressure, assessing both multiplicative and additive interactions. Results Long‐term exposure to PM with a diameter of ≤2.5 μm was significantly associated with higher odds of hypertension (odds ratio per 10 μg/m 3 increase, 1.100 [95% CI, 1.079–1.123]; P <0.001). Cold waves and elevation significantly modified this effect. The adverse association of PM with hypertension was synergistically amplified in regions with frequent cold waves ( P for interaction<0.05). Conversely, while higher elevation was independently associated with lower hypertension odds (odds ratio per 100 m increase, 0.995; P <0.001), it significantly potentiated the adverse association between PM and hypertension. Conclusions The association between air pollution and hypertension is significantly modified by local climatic and geographic conditions. The synergistic effect of PM and cold waves suggests current assessments may underestimate the burden in susceptible regions, necessitating integrated, climate‐informed public health strategies.