Cardiovascular disease deaths were significantly more common on days of high pollution and for the following 2 days, compared with other days, based on data from nearly 88,000 deaths over a 5-year period.
Previous research has shown the harmful effect of air pollution on human health in highly polluted areas, but Eastern Poland, a region with so-called “Polish smog” has exceptionally high levels of pollution. However, the specific impact of Polish smog, caused primarily by burning coal, on cardiovascular disease (CVD) mortality has not been well studied, said Michal Swieczkowski, MD, of the Medical University of Bialystok (Poland) in a presentation at the annual congress of the European Association of Preventive Cardiology.
Dr. Swieczkowski and colleagues reviewed all-cause deaths from five main cities in Eastern Poland during 2016-2020 for associations with pollution levels and days when deaths occurred. Mortality data were obtained from the Central Statistical Office. Air pollution concentrations for two types of particulate matter (PM2.5, PM10) and nitrogen oxide were collected from the Voivodeship Inspectorate for Environmental Protection. The main sources of the pollutants were road traffic and household heaters using coal or wood.
The final analysis included nearly 6 million person-years of follow-up. The researchers used a time-stratified case-crossover design. For each participant, the researchers compared levels of each pollutant on the day of the week a death occurred (such as a Wednesday) with pollutant levels on the same day of the week without any deaths in the same month (the remaining Wednesdays of that month). This design eliminated the potential confounding effects of participant characteristics, including other cardiovascular risk factors such as smoking and hyperlipidemia, and time trends. Essentially, participants “served as their own controls,” Dr. Swieczkowski said. The researchers conducted similar analyses for pollution levels 1 day and 2 days before a death occurred.
Overall, 87,990 deaths were identified during the study period; of these, 34,907 were from CVD, 9,688 from acute coronary syndromes, and 3,776 from ischemic stroke.
“Exposure to PM2.5 and PM10 was associated with increased mortality on the day of exposure, the next day, and up to 2 days after exposure,” said Dr. Swieczkowski.
Overall, an increase of 10 mcg/m3 in the three pollutants was significantly associated with increase in CVD mortality on the day of exposure to the increased pollution levels, with odds ratios of 1.034, 1.033, and 1.083 for PM2.5, PM10, and NO2, respectively (all P < .001).
The risks of dying from CVD were similar 1 and 2 days after the polluted day.
An increase in PM levels, but not NO2, was significantly associated with acute coronary syndrome (ACS) on the day of exposure to increased pollutants (ORs, 1.029 for PM2.5 [P = .002] and 1.015 [P = .049] for PM10). Both ischemic stroke and ACS mortality were significantly higher at 1 day after exposure, compared with other days. Ischemic stroke was associated with increases in PM2.5 and PM10, while ACS was associated with increases in PM2.5, PM10, and NO2.
When stratified by gender, the effects were more noticeable in women, Dr. Swieczkowski said. “Exposure to both types of particulate caused increased mortality due to acute coronary syndrome as well as ischemic stroke.” Among men, only death from acute coronary syndrome was significantly associated with exposure to increased particulate matter.
In a head-to-head comparison, women were more vulnerable to air pollution by up to 2.5%, he added.
When stratified by age, the effects of all three pollutants were associated with increased risk of death from ischemic stroke and ACS in participants older than 65 years. For those aged 65 years and younger, the only significant association was between ACS-associated mortality and ischemic stroke.
The results suggest “a special need for developing calculators to estimate the risk of CVD incidence depending on the place of residence that could be used for everyday practice,” said Dr. Swieczkowski. “Systemic changes should become a priority for policy makers, and, simultaneously, we as physicians should educate and protect our patients, especially those with high risk of cardiovascular disease,” he said.