Association between air pollution and case-specific mortality in north-eastern part of Poland. Case crossover study with 4,500,000 person-years of follow-up

Abstract Background Recent studies have reported associations between air pollution and daily mortality. The majority of them are conducted in highly polluted areas. Taking into consideration the scarce number of surveys from cities with moderate air quality we decided to conduct a study in this type of region. Purpose To assess the short-term impact of air pollution on cardiovascular (CVD), coronary artery-related (CAD), and cerebrovascular-related (CbVD) mortality. Methods The analysis with almost 4,500,000 person-years of follow-up with a time-stratified case-crossover design was performed. Results are reported as odds ratio (OR) associated with an increase in interquartile range (IQR). Results The analysed region was inhabited by almost 500,000 residents. From 2008 to 2017 in Bialystok, Lomza, and Suwalki we recorded 49,573 deaths – 34,005, 8,082, 7,486, respectively. The median daily concentrations of PM10 (23.8 μg/m3, IQR=16.9) was the highest in Lomza, Median daily concentration of PM2.5 was the highest in Bialystok (16.2 μg/m3, IQR=15.9). In the case of Suwalki, daily median PM2.5 concentration was 9.8 μg/m3 (IQR=8.7), and PM10 – 18.0 μg/m3 (IQR=14.3). The IQR increase in PM2.5 (OR 1.036, 95% CI 1.016–1.056, P<0.001) and PM10 concentration (OR 1.034, 95% CI 1.015–1.053, P<0.001) was associated with increased CVD mortality on lag 0 and this effect persisted on following days. The effects of PMs were more expressed in association with CAD-related mortality (OR for PM2.5 = 1.045, 95% CI 1.012–1.080, P=0.008), (OR for PM10 = 1.044, 95% CI 1.010–1.078, P=0.011) and CbVD mortality (OR for PM2.5 = 1.046, 95% CI 1.013–1.080, P=0.006), (OR=1.041 for PM10, 95% CI 1.002–1.082, P=0.038). Additionally, IQR increase in NO2 concentration was associated with increased CAD-related mortality at lag 0–1 (OR=1.055, 95% CI 1.004–1.108, P=0.032). The highest OR for PMs was noted in Suwalki compared to Bialystok and Lomza. The trend was noted regardless of the cause of death from lag 0 to lag 0–3. In a comparison of seasons, we noted higher CVD mortality OR in the cold season for PM10 in Suwalki (P=0.047) and Bialystok (p=0.001). However, the impact of NO2 (P=0.02) and PM10 (P=0.03) on CAD related mortality was higher in the warm season. Conclusions The impact of air pollution on CVD mortality is also observed in moderately polluted areas. PMs and NO2 had the greatest impact on CAD-related mortality. Differences in effect size and seasonality may depend on the source of air pollution. Funding Acknowledgement Type of funding sources: None.