The Risk of Getting Lung Cancer Lingers Years After a Smoker Quits

Ex-smokers can breathe easier about heart disease almost as soon as they stop puffing, but they may have to wait 20 years for a reduced risk of lung cancer, researchers have found. "It takes much longer to change the risk for lung cancer than it does for heart disease," said Dr Judith Ockene, director of the division of preventive and behavioral medicine at the University of Massachusetts Medical School. Her research, reported in the American Journal of Public Health, helps explain why death rates from those two diseases have diverged in the United States.

In the past two decades, death rates for coronary heart disease have probably dropped, while lung cancer death rates have continued to rise in certain groups of people, even though fewer are smoking. Dr Ockene and her collaborators studied 12,866 men in the Multiple Risk Factor Intervention Trial, MRFIT for short. MRFIT, sponsored by the National Heart, Lung and Blood Institute, was designed to test whether intervention programs - such as stop smoking classes - could reduce the death rate from coronary heart disease. The trial enrolled relatively healthy men ages 35 to 57 whose smoking, cholesterol level or blood pressure placed them at a high risk for coronary heart disease.

At the beginning of the MRFIT study, smokers were much more likely to die from coronary heart disease than non-smokers were. Just a year after quitting, however, the former smokers had a significantly lower risk of dying from coronary heart disease than the smokers. After not smoking for three years, the ex-smokers were less than half as likely as smokers to die from coronary heart disease. According to Dr. Ockene, within about five years, the heart disease risk for the ex smoker becomes very close to that of the risk of the never-smoker. When it came to lung cancer, however, the news for ex-smokers was not as encouraging. Even after several years of cessation, those men who stopped still did not have a lower risk of lung cancer than those who continued, Dr. Ockene reported.

The 119 men who died of lung cancer during the study's follow-up either were cigarette smokers or ex-smokers. No lung cancer deaths occurred in men who had never smoked cigarettes. Nicotine and carbon monoxide from smoking have an immediate adverse effect on the heart, so people who quit experience an immediate reduction in their risk of coronary heart disease.

The development of lung cancer, on the other hand, is a multi-step process that takes years. Once initiated, it apparently progresses even after a person stops smoking. "Lung cancer continues to be a major public health problem," Dr. Ockene and her colleagues wrote in the public health journal. Prevention of smoking and cessation at the youngest possible age for those individuals already smoking are the most important determinants of the future trends of lung cancer mortality.

Sources:

Fisher, Edwin B. American Lung Association 7 Steps to a Smoke-Free Life 1998

Cabbot, Jasmina B., and Evelyn N. Powers Smoking and Lung Cancer 2008