Spike in Heart Attacks, Stroke After Wildfire Smoke Exposure

Spike in Heart Attacks, Stroke After Wildfire Smoke Exposure

11 April 2018

Published https://www.medpagetoday.com/

USA – Exposure to smoke from wildfires was associated with a large increase in California emergency department (ED) visits for heart disease and stroke during the 2015 wildfire season, a review of more than 1 million ED visits in affected regions found.

During dense smoke days, a 42% increase in ED visits for heart attack and a 22% increase in visits for ischemic heart disease were found among individuals ages 65 and older, reported Ana G. Rappold, PhD, of the Environmental Protection Agency (EPA) in Durham, N.C., and colleagues.

Wildfire smoke exposure is an established risk factor for respiratory illnesses such as chronic obstructive pulmonary disease (COPD) and asthma, but the impact of breathing particulate air pollution from wildfire smoke on the risk for cardiovascular events — such as ischemic stroke, heart failure and myocardial infarction (MI) — is less well characterized.

“It is very common to see people in emergency rooms with COPD exacerbations or other respiratory problems around the time of wildfires, but stroke and MI are relatively uncommon,” co-author Zachary S. Wettstein, BA, of the University of California, San Francisco, told MedPage Today. “You need a very large number of emergency room visits to study this.”

The increase in hospital ED visits for stroke, heart attack and other cardiovascular causes was most pronounced in elderly people.

The population-based epidemiologic analysis, published in the Journal of the American Heart Association, was a joint collaboration between researchers at the University of California, San Francisco, the California Department of Public Health and the EPA.

Researchers reviewed more than 1 million ED visits from May 1 to September 30, 2015, when wildfires in northern and central California burned more than 800,000 acres.

All ED visits from the 8 California air basins (of 15) most exposed to smoke during the 2015 season were included. Of these, the North Coast, Sacramento Valley and San Joaquin Valley air basins had the largest and longest fires occurring during the study period. These were also areas with the largest population centers in the study region.

The main outcomes included ED visits for all-cause cardiovascular diagnoses and for individual cardiovascular diagnoses. Ischemic strike and transient ischemic attack were analyzed individually. Respiratory endpoints were included for external validity, and acute appendicitis and long-bone fracture were included as control endpoints.

The researchers used a quasi‐Poisson regression model for zip code–level counts of ED visits, adjusting for heat index, day of week, seasonality and population.

Satellite‐imaged smoke plumes obtained from the National Oceanic and Atmospheric Administration were classified as light, medium or dense based on model‐estimated concentrations of fine particulate matter. Relative risk was determined for smoky days for lag days 0 to 4.

Rates of ED visits by age‐ and sex‐stratified groups were also examined.

 Among the main findings:
  • Rates of all‐cause cardiovascular ED visits were elevated across all lags, with the greatest increase on dense smoke days and among those ages 65 and older at lag 0 (RR 1.15, 95% CI 1.09-1.22)
  • All‐cause cerebrovascular visits were associated with smoke, especially among those 65 and older (RR 1.22, 95% CI 1.00-1.49; dense smoke, lag 1)
  • Respiratory conditions were increased in those over 65, as anticipated (RR 1.18, 95% CI 1.08-1.28; dense smoke, lag 1)
  • No association was found for the control condition, acute appendicitis
  • Elevated risks for individual diagnoses included MI, ischemic heart disease, heart failure, dysrhythmia, pulmonary embolism, ischemic stroke and transient ischemic attack

Wildfire smoke contains air pollutants previously associated with respiratory and cardiovascular outcomes, including particulate matter, ozone, carbon monoxide, polycyclic aromatic compounds and nitrogen dioxide.

“The message to the public — particularly people with established heart, vascular or respiratory disease — is that they are at higher risk when exposed to poor air quality because of wildfire smoke,” said co-author Wayne Cascio, MD, director of the National Health and Environmental Effects Research Laboratory at the EPA. “They should consider taking action to lower their exposure.”

Cascio told MedPage Today that healthcare providers and public health officials need to make patients and the public aware of this risk.

“At the national level, we have increasing wildfire incidence and a population that is aging,” Cascio said, “and this is occurring at the same time that the interface between human habitation and the forests susceptible to wildfires are increasingly merging,” noting that more people are living in wildland-urban interface areas.

“Baby boomers are going to continue to age, and there is going to be a lot of heart disease and pulmonary disease in this group,” he said. “This is a current challenge to public health officials, but it is going to be with us for a while.”

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