Ambient temperature variation (DTR, TCN, and TV0-t), air pollution, and hospitalization for pulmonary hypertension in a warm and humid city in China: A single-center time-stratified case-cross study

Background Despite robust evidence linking temperature variation and ambient air pollution to cardiopulmonary mortality, quantitative evidence regarding their effects on pulmonary hypertension (pH) hospitalizations is still scarce. Methods In this single-center, time-stratified case-crossover study of 15,956 pH patients in Shanghai, China (2014–2023), we employed conditional Poisson regression combined with distributed lag nonlinear models to evaluate the relationship between temperature variation (DTR, TCN, and TV 0-t ) and six critical air pollutants with PH hospitalizations. We further performed stratified analyses to identify vulnerable subgroups. Results Both temperature variation and air pollution were significantly associated with PH hospitalizations across multiple lag periods. The highest relative risks (RR) were observed at a cumulative lag of 7 days for DTR (RR = 1.102, 95% CI: 1.074–1.130), at a single-day lag of 5 days for TCN (1.012, 1.002–1.021), and at a cumulative lag of 0–10 days for TV 0-t (1.612, 1.384–1.878). Three distinct lag-response patterns emerged for air pollutants: PM 2.5 , NO₂, and CO exhibited acute effects peaking on the exposure day; O₃ exhibited a cumulative effect with a peak at lag 4 days; and PM₁₀ and SO₂ displayed a delayed effect, with the highest risk at lag 7 days. Subgroup analyses revealed that temperature variation predominantly affected females, seniors (≥65 years), and the uninsured patients during cold seasons, whereas air pollution disproportionately impacted females, younger individuals, and the uninsured during warm seasons. Conclusions In this 10-year analysis, short-term temperature variation and air pollution were significantly associated with higher PH hospitalization risk, particularly in females and the uninsured, highlighting the need for targeted protective measures against climate change and air pollution.