A case-crossover study on the effect of short-term exposure to moderate levels of air pollution on the risk of heart failure

Aims: Exposure to high levels of air pollution in industrialized urban areas is associated with an increased risk of heart failure (HF). On most days, the majority of European cities are only moderately affected by air pollution. The aim of this study was to evaluate the association between short-term exposure to moderate levels of air pollution with the risk of HF in a city with good air quality.

Methods and results: We recruited 576 patients (median age 82 years; 58.2% men) admitted to a large university hospital in Central Germany for HF to participate in a hospital-based, bidirectional, case-crossover study. Diagnosis of HF and symptom onset were verified individually. The effect of short-term exposure to nitrogen dioxide (NO₂ ), particulate matter (PM₁₀ ), and ozone (O₃ ) on the risk of HF was estimated using linear and non-linear (categorized) multivariate analyses for three different lag times (1, 2, and 3 days before HF onset). Air pollution variables were adjusted to the date of HF symptom onset. During the study period, the average daily concentration of air pollutants was only moderate and reflects the average European background air pollution. In particular, the concentration of air pollutants ranged from 2 to 63.39 μg/m³ (median = 17.46 μg/m³ ) for NO₂ , from 2 to 125.88 μg/m³ (median = 44.61 μg/m³ ) for O₃ , and from 2.21 to 166.79 μg/m³ (median = 18.67 μg/m³ ) for PM₁₀ . We did not find a linear or non-linear association between short-term exposure to NO₂ , O₃ , or PM₁₀ and risk for HF at all lag times in the overall population and subgroups.

Conclusions: In an area with only moderate air pollution, short-term exposure to major air pollutants does not increase the risk for HF. Future studies should focus on a potential threshold effect of air pollution on HF risk as a basis for evidence-based development of statutory limits in highly polluted areas.