Short-Term Exposure to Air Pollution Increases Mortality From Hypertension and its Multiorgan Complications: A Case Crossover Study of 2.1 Million Deaths in China.

Abstract (English)

BACKGROUND: Short-term air pollution exposure is a known trigger for cardiovascular events, yet how this risk varies across different progression stages of hypertensive patients remains unclear. OBJECTIVES: This study sought to quantify the mortality risk and burden due to hypertensive diseases of different progression stages in association with air pollution. METHODS: We conducted a nationwide, individual-level, time-stratified, case-crossover study including >2.1 million hypertension-related deaths across mainland China (2013-2019). Daily concentrations of fine particulate matter (PM_2.5), inhalable particulate (PM₁₀), NO₂, and O₃ were estimated using high-resolution spatiotemporal models (1 × 1 km). Conditional logistic regression was used to quantify the associations. RESULTS: We observed a clear, stepwise risk gradient. For PM_2.5, the mortality risk per interquartile range increase rose from 1.39% (95% CI: 0.55%-2.24%) in uncomplicated primary hypertension to 2.62% (95% CI: 2.20%-3.05%) in hypertensive heart disease and 3.03% (95% CI: 1.53%-4.56%) in hypertensive kidney disease, reaching 5.01% (95% CI: 1.96%-8.16%) in hypertensive heart and kidney disease with concurrent cardiorenal failure at lag 02 days (average of lag 0-2 days). This high-risk phenotype also had the highest attributable fraction, with 4.20% (95% CI: 3.55%-4.85%) of deaths attributable to PM_2.5. Furthermore, NO₂ consistently showed the strongest associations among 4 air pollutants. We observed that the exposure-response curves for all 4 pollutants demonstrated approximately linear relationships with hypertension mortality, with no apparent evidence of a threshold. Hypertensive patients of female sex, age ≥65 years, northern residence, lower educational attainment, and no spousal support, and patients during the cold season were more vulnerable. CONCLUSIONS: Air pollution acts as an acute stressor superimposed on hypertensive patients, creating a mortality risk gradient determined by the severity of comorbidity. These findings highlight the need for targeted risk stratification, identifying patients with concurrent cardiorenal failure as a priority group for precision-based environmental health advisories and targeted clinical management.