Continued Cigarette Smoking and the Risk for a Second Heart Attack

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The summary below is from the full report titled "Smoking Status and Risk for Recurrent Coronary Events after Myocardial Infarction." It is in the 17 September 2002 issue of Annals of Internal Medicine (volume 137, pages 494-500). The authors are TD Rea, SR Heckbert, RC Kaplan, NL Smith, RN Lemaitre, and BM Psaty.

What is the problem and what is known about it so far?

People who smoke cigarettes are more likely than nonsmokers to develop blocked blood vessels to the heart and to suffer heart attacks, but these risks decrease to the level of nonsmokers within 2 to 3 years of quitting smoking. Some studies suggest that after a heart attack, persistent smoking does not continue to elevate risk. It is not known whether this impression is correct or, if not, how fast the potential benefits of quitting occur.

Who was studied?

2619 members of a large health maintenance organization (HMO). All had been discharged from the hospital after having a heart attack, were 30 to 79 years of age, had belonged to the HMO for at least 1 year, had attended at least four outpatient visits, and had information recorded about smoking habits.

How was the study done?

The researchers evaluated medical records to classify participants as nonsmokers (who had never smoked at any time), former smokers (who had quit before their heart attack), quitters (who had quit after their heart attack), or active smokers (who smoked before and after their heart attack). Information on subsequent nonfatal or fatal heart attacks or other bad cardiac outcomes was also recorded. The researchers calculated how often these events occurred in each smoking category. The risk for recurrent heart problems in each group of smokers was compared to that in the nonsmokers. The timing of these events was classified as 0 to 6 months, 6 to 18 months, 18 to 36 months, or more than 36 months after quitting cigarette smoking.

What did the researchers find?

At the time of hospitalization for a heart attack, about one third of the patients were nonsmokers, one third were former smokers, and one third were active smokers. Of the active smokers, 39% had quit during hospitalization and 61% continued to smoke. After hospitalization, 272 nonfatal heart attacks, 94 fatal heart attacks, and 67 other heart-related deaths occurred. Compared to nonsmokers, the risk for a bad cardiac outcome was 1.43 times as high among quitters and 1.51 times as high among active smokers. Former smokers had the same risk as nonsmokers. Among those who quit smoking after their heart attack, the risk gradually fell to about the level of the nonsmoker after 36 months.

What were the limitations of the study?

Information on smoking habits was determined from medical records and may not have been accurate. The researchers could not be certain that doctors who convinced their patients to quit smoking also provided better care; this would make it appear that risk improved because of smoking cessation when another factor may actually have been more important.

What are the implications of the study?

Since continued smoking after a heart attack increases the risk for further cardiac problems and this risk can be decreased by quitting, doctors should make every effort to help their patients quit smoking.