WEDNESDAY, Feb. 23 (HealthDay News) -- A major analysis of data on potential triggers for heart attacks finds that many of the substances and activities Americans indulge in every day -- coffee, alcohol, sex, even breathing -- can all help spur an attack.

Because so many people are exposed to dirty air, air pollution while stuck in traffic topped the list of potential heart attack triggers, with the researchers pegging 7.4 percent of heart attacks to roadway smog.

But coffee was also linked to 5 percent of attacks, booze to another 5 percent, and pot smoking to just under 1 percent, the European researchers found.

Among everyday activities, exerting yourself physically was linked to 6.2 percent of heart attacks, indulging in a heavy meal was estimated to trigger 2.7 percent, and sex was linked to 2.2 percent.

The researchers stressed that the risk for heart attack from any one of these factors to a particular person at any given time is extremely small. But spread out over the population, they can add up.

For example, air pollution is a minor trigger for heart attacks, but since so many people are exposed to smog, it triggers many more heart attacks than other more potent triggers, such as alcohol and cocaine.

"Small risks can be highly relevant if they are widely distributed in the population," explained lead researcher Tim S. Nawrot, assistant professor of epidemiology at the Hasselt Centre for Environmental Sciences at Hasselt University in Diepenbeek, Belgium.

Commenting on the study, Dr. Gregg Fonarow, spokesman for the American Heart Association and professor of cardiology at the University of California, Los Angeles, added that "based on these findings, improvement in air quality and reduction in traffic may not just help the environment and increase quality of life, but also substantially decrease the incidence of [heart attack]."

The report is published in the Feb. 24 online edition of The Lancet.

In their research, Nawrot's team looked at 36 studies examining environmental triggers for heart attacks. In their review, known as a meta-analysis, the researchers looked for common threads that could establish how these factors might rank in risk.

In terms of risk, the team found that air pollution increased a person's risk of having a heart attack by just under 5 percent. In contrast, coffee increased the risk by 1.5 times, alcohol tripled the risk, and cocaine use increased the odds for heart attack 23-fold.

However, because only a small number of people in the entire population are exposed to cocaine, while hundreds of millions are exposed to air pollution daily, air pollution was estimated to cause more heart attacks across the population than cocaine.

Even emotional states can sometimes trigger a heart attack, the team found. For example, negative emotions in general were linked to almost 4 percent of heart attacks while anger, specifically, was linked to just over 3 percent. Even "good" emotional states were tied to 2.4 percent of heart attacks, the study authors noted.

Although exposure to secondhand smoke was not included in the analysis, the effects are probably of the same magnitude as air pollution, the authors added. Where bans on smoking in public places exist, the rate of heart attacks has dropped an average of 17 percent, they noted.

Dr. Andrea Baccarelli, the Mark and Catherine Winkler associate professor of environmental epigenetics at the Harvard School of Public Health and coauthor of an accompanying journal editorial, said that "this work stands as a warning against overlooking the effects of moderate risks when they affect the entire population."

At the same time, the researchers show that powerful triggers such as cocaine are very detrimental for those (relatively few) subjects who are exposed to them, he said.

"However, because they are infrequent, they cause a relatively small number of [heart attacks] in the population. At the opposite, ubiquitous triggers such as air pollution affect all the subjects in a city with high air pollution levels. Although the risk due to air pollution on each individual is moderate to small, the number of events triggered by air pollution in that city will be sizable," Baccarelli said.

More information

For more information on heart attack, visit the American Heart Association.