Why you are likely to have heart attack if exposed to air pollution over time
Increased exposure to air pollution has been linked to the more rapid onset of atherosclerosis, more commonly known as hardening of the arteries, according to a new study published April 26 in PLOS Medicine.
Hardening of the arteries is a leading cause of heart attacks and strokes, and the study also found that its progression can be slowed by decreasing exposure to air pollution, says lead author Sara Adar, the John Searle Assistant Professor of Epidemiology at the University of Michigan (U-M) School of Public Health in Ann Arbor.
"Our findings help us to understand how it is that exposures to air pollution may cause the increases in heart attacks and strokes observed by other studies."
Cardiovascular disease (CVD) – disease of the heart and/or the blood vessels – is a major cause of illness and death worldwide. For example, the leading cause of death among adults in the U.S. is coronary artery disease, a CVD involving narrowing of the arteries due to fatty deposits that build up inside them; thus, slowing blood supply to the heart, which can eventually cause a heart attack.
The fourth leading cause of death in the US is stroke, a CVD in which fatty deposits build up inside the arteries, resulting in an interruption of the brain's blood supply. Factors that increase risk of stroke include smoking, high blood pressure, high blood cholesterol levels, having diabetes, being overweight and physically inactive.
There are ways to treat CVD, which include lifestyle changes and taking medications to reduce blood pressure and/or cholesterol.
For this study, researchers followed 5,362 participants between the ages of 45 and 84 from six US metropolitan areas, assessing them over time to see if exposure to certain risk factors affected their risk of developing a particular disease.
After adjusting for possible influencers (e.g. smoking, sex, age, socioeconomic status, etc.), the results of the study found that exposure to air pollution by participants resulted in faster hardening of their arteries each year.
Even for participants living in the same metropolitan area, it was those living in the more polluted parts who experienced a quicker thickening of their arteries over time.
For those with reduced exposure to air pollution, the progression of atherosclerosis was also reduced.
"Linking these findings with other results from the same population suggests that persons living in a more polluted part of town may have a 2% higher risk of stroke as compared to people in a less polluted part of the same metropolitan area," Adar explained.
The researchers concluded that if these findings are confirmed with a longer, 10-year follow up in this group of participants, they may explain why long-term exposure to air pollutions is linked to cardiovascular events like heart attacks and strokes, conclude the researchers.
"Fine Particulate Air Pollution and the Progression of Carotid Intima-Medial Thickness: A Prospective Cohort Study from the Multi-Ethnic Study of Atherosclerosis and Air Pollution"; Sara D. Adar, et al, PLOS Medicine 10(4): e1001430, published online 23 April 2013; DOI: 10.1371/journal.pmed.1001430; Link to Article.