Ambient air pollution and emergency department visits and hospitalisation for cardiac arrest: a population-based case-crossover study in Reykjavik, Iceland

Abstract

Objectives: To assess the association between traffic-related ambient air pollution and emergency hospital visits for cardiac arrest.

Design: Case-crossover design was used with a lag time to 4 days.

Setting: The Reykjavik capital area and the study population was the inhabitants 18 years and older identified by encrypted personal identification numbers and zip codes.

Participants and exposure: Cases were those with emergency visits to Landspitali University Hospital during the period 2006-2017 and who were given the primary discharge diagnosis of cardiac arrest according to the International Classification of Diseases 10th edition (ICD-10) code I46. The pollutants were nitrogen dioxide (NO₂), particulate matter with aerodynamic diameter less than 10 µm (PM₁₀), particulate matter with aerodynamic diameter less than 2.5 µm (PM_2.5) and sulfur dioxide (SO₂) with adjustment for hydrogen sulfide (H₂S), temperature and relative humidity.

Main outcome measure: OR and 95% CIs per 10 µg/m³ increase in concentration of pollutants.

Results: The 24-hour mean NO₂ was 20.7 µg/m³, mean PM₁₀ was 20.5 µg/m³, mean PM_2.5 was 12.5 µg/m³ and mean SO₂ was 2.5 µg/m³. PM₁₀ level was positively associated with the number of emergency hospital visits (n=453) for cardiac arrest. Each 10 µg/m³ increase in PM₁₀ was associated with increased risk of cardiac arrest (ICD-10: I46), OR 1.096 (95% CI 1.033 to 1.162) on lag 2, OR 1.118 (95% CI 1.031 to 1.212) on lag 0-2, OR 1.150 (95% CI 1.050 to 1.261) on lag 0-3 and OR 1.168 (95% CI 1.054 to 1.295) on lag 0-4. Significant associations were shown between exposure to PM₁₀ on lag 2 and lag 0-2 and increased risk of cardiac arrest in the age, gender and season strata.

Conclusions: A new endpoint was used for the first time in this study: cardiac arrest (ICD-10 code: I46) according to hospital discharge registry. Short-term increase in PM₁₀ concentrations was associated with cardiac arrest. Future ecological studies of this type and their related discussions should perhaps concentrate more on precisely defined endpoints.

Keywords: adult cardiology; epidemiology; registries.