Study results released today by the American Heart Association suggest that exposure to even a small amount of smoke - whether it's from your own cigarette or someone else's - greatly increases your risk of dying from cardiovascular disease. The same goes for breathing in air polluted with carbon monoxide emissions.
"It doesn't require extreme exposure to have significant cardiovascular effects. Even passive exposures to ambient air pollution and secondhand smoke contribute to significant increases in cardiovascular mortality," study author C. Arden Pope III, PhD, says in a statement.
Researchers from Brigham Young University analyzed data from more than 1 million adults, noting their smoking habits and exposure to tiny, toxic particles (fine particulate matter) from secondhand smoke and air pollution.
They determined the relative risks of cardiovascular-related death from different amounts of cigarette smoking and compared them to the dangers of inhaling various levels of secondhand smoke and polluted air. They also took into consideration other known heart disease risk factors, such as diet and body mass index .
Previous studies have shown that cigarette smoking is a leading contributor to cardiovascular disease and related events, such as heart attacks and strokes. Active smoking fills the lungs with large amounts of fine particulate matter. These particles can go deep within the lungs, causing respiratory problems. They can also lead to the development of clogged arteries (atherosclerosis ).
Secondhand Smoke Raises Risk By 20 percent
The new study provides further evidence that just being near someone who smokes (secondhand smoke) significantly increases your risk for heart attacks and strokes. Breathing in levels of smoke far less than what equals one cigarette a day increases your risk of cardiovascular disease by about 20 percent to 30 percent, compared to people who are not exposed, the researchers found. They say that even low levels of smoke can prompt dangerous biological changes - such as inflammation and increased platelet activity - which make heart attacks more likely.
Researchers noted the steepest increase in risk in those who had relatively low levels of smoke exposure. In other words, breathing in even small amounts of smoke can have profoundly deleterious effects on health. But those exposed to low levels are not the only ones that should worry - the risk increases further the more smoke one inhales.
The findings, which appear in the journal Circulation, underscore the importance of avoiding secondhand smoke, and could have big implications for public policies on air quality. Study authors say the findings also deliver an important message for smokers:
"A critical finding of our study is that smoking is unhealthy even at small amounts," Pope said. "Reducing the amount one smokes does some good, but the biggest benefits come from stopping completely."
Among smokers, the increases in heart disease-related death risk were as follows:
• Three or less cigarettes a day: 64 percent increased risk
• Half pack (about 8-12 cigarettes daily): 79 percent increased risk
• Full pack (about 18-22 cigarettes daily): nearly 100 percent increased risk
In an accompanying editorial, Annette Peters, PhD, from the German Research Center for Environmental Health, Institute of Epidemiology, writes that the findings from this study and another on carbon monoxide exposure "highlight the consistently emerging evidence that both indoor and outdoor air quality is a modifiable risk factor for cardiovascular disease." She believes that many worldwide policy makers still underestimate the health risks associated with low-dose smoking, secondhand smoke, and air pollution.
Carbon monoxide emissions from traffic create dirty, smoggy air pollution. Researchers have also found that breathing in such air for even short periods of time - at levels deemed safe by current outdoor air quality standards - increases an older adult's chances of being admitted to the hospital for heart problems.
By Kelli Stacy
Reviewed by Elizabeth Klodas
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