For heart health: avoid tobacco smoke, pollution

If you want to dramatically lower the odds that you'll die of heart disease, go live someplace where public smoking is banned.

In a study of more than a million people, researchers found that even low levels of smoke from co-workers' cigarettes can substantially raise your risk of death from heart disease.

While you're packing to move, look for a place without much pollution, because a second study involving more than 9 million people in 126 counties across the U.S. has shown a direct correlation between the amount of carbon monoxide in the air and daily admissions to emergency rooms for heart problems.

Both studies are reported Monday in the American Heart Association's medical journal, Circulation.

In the first study, Dr. C. Arden Pope III from Brigham Young University in Arden, Utah and colleagues analyzed data on roughly 1.2 million adults that had been collected over 25 years as part of a study by the American Cancer Society.

"We've known for a long time that smoking exposes your lungs to massive amounts" of fine particulates and increases your risk of dying from heart disease, Pope told Reuters Health. Compared to active smoking, the dose of particulates to the lungs with passive smoking is "much, much smaller," he added.

Even so, earlier studies have suggested surprisingly high rates of heart disease deaths from passive smoking, out of line with the much smaller dose of particulates. So, Pope said, he and his colleagues decided, "We're going to take the largest data set available" - from the American Cancer Society's Cancer Prevention Study II - "and look at the effects of different increments of exposure" to smoke and other pollutants on risk.

They discovered, Pope said, that "the biggest increases in risk occur at lighter levels of exposure."

For example, compared to people who have never smoked, people who smoke up to 3 cigarettes per day increase their risk of dying from heart disease by 65 percent. Doubling or tripling the amount of cigarettes per day doesn't double or triple the risk, however; instead, for people smoking 8 to 12 cigarettes per day, the risk for heart disease death is increased to "only" 79 percent compared to never-smokers.

People smoking 18 to 22 cigarettes per day - about a pack - have double the risk compared to never smokers.

"Even more amazing," said Pope, was that compared to people who had never smoked and had no heavy exposure to smokers, passive smokers had a 20 to 30 percent higher risk of heart disease-related deaths. The strongest effect is seen in spouses of smokers.

The research team points out that the relationship between dose of tobacco particulates and the response in terms of increased risk is very steep. "With light exposure, the result is substantial," Pope said, but with incremental increases in exposure, the increases in risk, while already high, start to rise more gradually.