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The long reach of cigarette smoke

(This article was first printed in the September 2004 issue of the Harvard Heart Letter. For more information or to order, please go to www.health.harvard.edu/heart.)

New research extends the case against secondhand smoke by linking it to heart disease.

Smoking, first fingered as a prime cause of lung cancer, also contributes to heart disease. Compared with nonsmokers, smokers have double the chances of having a heart attack or stroke, developing other forms of heart disease, or dying from heart disease. Several 2004 studies indicate that smokers also harm the hearts of nonsmokers around them.

The health effects of secondhand smoke are at the center of an acrimonious and politically charged debate. Studies linking secondhand smoke to disease are routinely used to support local or statewide bans on smoking in public places. Inconclusive or negative studies are cited to challenge such laws. The studies aren’t the final nails in the coffin for secondhand smoke. But they do nudge the debate forward.

Smoking ban and heart attacks

In the city of Helena, Montana, a law that banned smoking in restaurants, bars, offices, and other public venues was in place for six months before a judge overturned it. During the ban, the number of people seen for heart attacks at the only cardiac care hospital for miles was only half of what it had been before the law was enacted and after it had been struck down.

Writing in the April 24, 2004British Medical Journal, the local cardiologists who carried out the widely publicized study acknowledged its limitations. These include Helena’s small size and lack of knowledge about heart attack victims’ exposure to secondhand smoke. That said, they conclude that the establishment of smoke-free public places could have a quick and beneficial effect on heart disease.

Living with a smoker

New Zealand researchers tried to gauge the effects of secondhand smoke a different way. Using data from a nationwide census in 1981 and another in 1996, they compared death rates among two groups of people who said they had never smoked — those who lived with smokers and those who lived with nonsmokers. Death rates were 15% higher among those who breathed secondhand smoke at home. This report, which also appeared in the April 24, 2004 British Medical Journal, may underestimate the impact of secondhand smoke because it didn’t take into account nonsmokers’ exposure at work or elsewhere outside the home.

Evidence in the blood

Blood levels of cotinine (KOE-tin-een), a substance formed when the body breaks down nicotine, are one way to measure exposure to smoke. A team of British researchers looked at cotinine levels in more than 2,000 men who said they didn’t smoke to gauge the impact of secondhand smoke.

Cotinine levels were closely linked with exposure to secondhand smoke and to heart disease. After 20 years of follow-up, 18% of the men with the highest cotinine levels had developed heart disease — the same percentage as light smokers — compared to 10% of those with the lowest levels. The British Medical Journal published this work online on June 30, 2004.

Impact of secondhand smoke

Cigarette smoke contains more than 4,000 substances. Nicotine, one of the best known, is the prime addictive element. A host of others either generate free radicals or get the body to do so. These highly reactive chemicals are thought to set off early steps of atherosclerosis. Cigarette smoke also revs up inflammation, another process at the root of heart disease.

One of the mysteries of secondhand smoke is how it can cause nearly the same level of damage as smoking. A leading idea is that even a brief exposure to secondhand smoke can suddenly limit the flexibility of arteries.

Several studies support this line of thinking. One of the most telling looked at how the heart’s arteries respond to stress before and after brief exposures to secondhand smoke. Smokers weren’t affected — blood flow through their coronary arteries didn’t change after sitting for half an hour in a smoke-filled room. In nonsmokers, though, breathing cigarette smoke restricted the ability of coronary arteries to widen and carry more blood when stressed.

Secondhand smoke also makes blood more likely to clot. The combination of less flexible arteries and an increased tendency to form blood clots creates a double whammy that could trigger a heart attack, especially in nonsmokers who already have heart disease.

The Centers for Disease Control and Prevention (CDC) estimates that secondhand smoke is responsible for 35,000 deaths a year. It’s a special risk for people who work in smoke-filled rooms, like waitresses and bartenders. In fact, the CDC now urges people with heart disease or at high risk for it to stay away from indoor settings where smoking is allowed.

This work on secondhand smoke won’t end the debate on who can smoke where. But it does add to the evidence that tobacco smoke affects more than just smokers.

If you smoke, you need to know that your habit directly affects the health of others. If you don’t smoke, don’t hesitate to ask a smoker to “take it outside,” especially if you have heart disease. The evidence is in your corner that secondhand smoke is more than just a nuisance — it’s also bad for you.

(This article was first printed in the September 2004 issue of the Harvard Heart Letter. For more information or to order, please go to www.health.harvard.edu/heart.)

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