Joint effects of air pollution and compound dry-hot extremes on cardiovascular disease risk across adults: a cohort study in China

Abstract

Compound dry-hot extremes (CDHEs) and ambient air pollution are growing public health threats under global climate change, yet their joint impacts on cardiovascular disease (CVD) risk remain poorly understood. We conducted a nationwide longitudinal cohort study using data from the China Family Panel Studies (CFPS), including 9,265 Chinese adults aged ≥ 18 years with 69,297 repeated observations between 2010 and 2018. We evaluated the independent, joint and heterogeneous effects of multi-dimensional CDHE metrics (accumulated days, frequency and average severity) and key air pollutants (e.g., PM 2.5 ) on incident CVD. Mixed-effects Cox models, interaction analyses and stratified analyses were performed to examine the study objectives. Per interquartile range (IQR) increment in CDHE cumulative days and PM 2.5 concentration were associated with 30% (HR = 1.30, 95% CI: 1.20–1.41) and 54% (HR = 1.54, 95% CI: 1.42–1.67) higher CVD risk, respectively, with CDHE accumulated days rather than event frequency or intensity driving the long-term cardiovascular damage. Both exposures showed the strongest risk elevations for coronary heart disease, with 72% (HR = 1.72, 95% CI: 1.44–2.07) and 75% (HR = 1.75, 95% CI: 1.46–2.11) risk increments per IQR for CDHE cumulative days and PM 2.5 , respectively. Critically, concurrent high exposure to CDHEs and PM 2.5 induced synergistic elevated CVD risk, with the joint hazard ratio reaching 1.92 (95% CI: 1.67–2.21), and this synergistic pattern was consistent across PM 1 , PM 10 , NO 2 and O 3 . Stratified analyses further revealed that older adults, males, urban residents, smokers, drinkers, physically inactive and overweight individuals were more susceptible to these environmental risks. Compound dry-hot extremes and ambient air pollution are independent risk factors for incident CVD in Chinese adults. Concurrent exposure to these two environmental stressors induces synergistic cardiovascular damage, with CDHE accumulated days being the primary driver. These findings pointing to the necessity for integrated public health strategies that simultaneously target air quality improvement and climate resilience.