Short-term air pollution acts as an acute stressor in individuals with hypertension and amplifies mortality risk based on existing conditions, according to a nationwide study of 2.1 million hypertension-related deaths in China published Feb. 25 in JACC.

This individual-level, time-stratified, case-crossover study included more than 2.1 million hypertension-related deaths across mainland China from 2013 to 2019. Data were collected from the National Death Registration Information System. Daily concentrations of fine particulate matter (PM_2.5), inhalable particulate (PM₁₀), nitrogen dioxide (NO₂) and ozone (O₃) were calculated using high-resolution spatiotemporal models (1 × 1 km), and conditional logistic regression was used to quantify associations.

Results showed a clear, stepwise risk gradient. For PM_2.5, the per-interquartile mortality risk rose from 1.4% in uncomplicated primary hypertension to 2.6% in hypertensive heart disease, and 3% in hypertensive kidney disease, reaching 5% hypertensive heart and kidney disease with concurrent cardiorenal failure at lag 02 days (average of lag 0-2 days). This high‑risk group also had the largest share of deaths attributed to PM_2.5 at 4%.

Of note, patients who were female, age 65 or older, lived in northern regions, had lower education levels, lacked spousal support or were exposed during cold season were more vulnerable.

Among the four air pollutants studied, NO₂ showed the strongest consistent association with mortality. For all pollutants, the exposure‑response curves were roughly linear with no clear threshold.

These findings highlight the need for targeted risk stratification. Patients with concurrent cardiorenal failure should be identified as a priority group for targeted clinical management and precision-based environmental health advisories.

Xiaowei Xue, et al., note that their findings "...confirm and extend previous research linking air pollution to hypertension mortality." In addition to confirming previous research, their study results "...suggest that the severity of comorbidity is a key determinant of vulnerability to environmental stress in hypertensive patients."