Association between long-term exposure to ambient air pollution and clinical outcomes among patients with heart failure: Findings from the China PEACE Prospective Heart Failure Study

Abstract

Background: The health effects of air pollution on heart failure (HF) patients have not been adequately studied.

Objectives: We assessed the associations between long-term air pollution exposure and prognosis in HF patients.

Methods: HF patients were prospectively recruited from 52 hospitals throughout China between August 2016 and May 2018. The participants were followed up for 12 months after discharge from index hospitalization. Long-term air pollution was calculated as annual average level of air pollution before the date of the index hospitalization. Outcomes were defined as HF readmission, cardiovascular death, and composite events. Cox proportional hazards model was applied to quantify the associations between air pollution exposure and clinical outcomes.

Results: Of 4866 patients included in the analysis, mean age was 65.2 ± 13.5 years, and 62.5% were male. During 1-year follow-up, 1577 (32.4%) participants were readmitted for HF and 550 (11.3%) died from cardiovascular disease. Though no associations between long-term air pollution and HF readmission in the overall participants, geographic and age heterogeneity in the long-term effects of air pollutants on HF readmission was observed. Air pollutants included PM_2.5 [HR (hazard ratio) = 1.146, 95% CI (confidence interval): 1.044, 1.259], PM₁₀ (HR = 1.120, 95% CI: 1.043, 1.203), SO₂ (HR = 1.808, 95% CI: 1.190, 2.747), and CO (HR = 3.596, 95% CI: 1.792, 7.218) were associated with higher risk of HF readmission in South China, but not in North China, where people spend less time outdoors and have limited indoor-outdoor ventilation. PM_2.5, PM_10, O₃, and CO among patients ≥ 65 years were found to be associated with higher risk of HF readmission. The effects on composite outcomes were broadly consistent with that of HF readmission. Cardiovascular death was not significantly associated with air pollution in the overall or subgroups.

Discussion: Among HF patients who were older, living in South China, more HF readmissions occurred with higher long-term air pollution exposure. The findings suggest that the elderly patients and those living in South China should particularly enhance their personal protection against air pollution.

Keywords: Air pollution; Cardiovascular death; Heart failure; Long-term; Readmission.