Analysis of the relationship between ambient air pollution and the severity of heart failure decompensations in two Spanish metropolises (Barcelona and Madrid).

Objectives: To analyze whether the high levels of air pollutants are related to a greater severity of decompensated heart failure (HF).

Method: Patients diagnosed with decompensated HF in the emergency department of 4 hospitals in Barcelona and 3 in Madrid were included. Clinical data (age, sex, comorbidities, baseline functional status), atmospheric (temperature, atmospheric pressure) and pollutant data (SO, NO, CO, O, PM, PM) were collected in the city on the day of emergency care. The severity of decompensation was estimated using 7-day mortality (primary indicator) and the need for hospitalization, in-hospital mortality, and prolonged hospitalization (secondary indicators). The association adjusted for clinical, atmospheric and city data between pollutant concentration and severity was investigated using linear regression (linearity assumption) and restricted cubic spline curves (no linearity assumption).

Results: A total of 5292 decompensations were included, with a median age of 83 years (IQR=76-88) and 56% women. The medians (IQR) of the daily pollutant averages were: SO=2.5μg/m (1.4-7.0), NO=43μg/m (34-57), CO=0.48mg/m (0.35-0.63), O=35μg/m (25-48), PM=22μg/m (15-31) and PM=12μg/m (8-17). Mortality at 7 days was 3.9%, and hospitalization, in-hospital mortality, and prolonged hospitalization were 78.9, 6.9, and 47.5%, respectively. SO was the only pollutant that showed a linear association with the severity of decompensation, since each unit of increase implied an OR for the need for hospitalization of 1.04 (95% CI 1.01-1.08). The restricted cubic spline curves study also did not show clear associations between pollutants and severity, except for SO and hospitalization, with OR of 1.55 (95% CI 1.01-2.36) and 2.71 (95% CI 1.13-6.49) for concentrations of 15 and 24μg/m, respectively, in relation to a reference concentration of 5μg/m.

Conclusion: Exposure to ambient air pollutants, in a medium to low concentration range, is generally not related to the severity of HF decompensations, and only SO may be associated with an increased need for hospitalization.