Lung cancer is responsible for more deaths per year than any other type of cancer. According to the American Cancer Society, in 2005, more than 170,000 people will be diagnosed with lung cancer and more than 160,000 people will die from the disease.

An estimated 90% of lung cancer cases are tobacco-related, yet the prevalence of cigarette smoking is still high. Many smokers either cannot or will not quit. But what about cutting down—surely a more realistic and attainable goal for many smokers than quitting completely? Could smoking fewer cigarettes per day reduce a person’s risk for lung cancer?

In an article published in the September 28, 2005 Journal of the American Medical Association , researchers report that heavy smokers (those who smoked 15 or more cigarettes per day) significantly decreased their risk for lung cancer by reducing the number of cigarettes they smoked per day by half. They also found, however, that all smokers, even ex-smokers who had not smoked a cigarette in years, had a significantly higher risk for lung cancer than people who had never smoked.

About the Study

The researchers conducted an observational study of 8,563 women and 11,151 men, aged 20-93, who had participated in the Copenhagen Centre for Prospective Population Studies. All participants underwent two examinations (the second either five or ten years after the first) between 1964 and 1988.

At each examination, the study participants were asked whether they smoked and if so, how much. Based on their responses, the researchers classified the participants into six categories:

Continued heavy smokers (smoked 15 or more cigarettes per day throughout the study)

Reducers (cut down from 15 or more cigarettes per day by at least half, without quitting)

Continued light smokers (smoked 1-14 cigarettes per day throughout the study)

Quitters (quit smoking during the study)

Stable ex-smokers (quit smoking before the study)

Never smokers

The researchers recorded new cases of lung cancer among the study participants for an average follow-up period of 18 years. They then compared new cases of lung cancer among the six categories of smokers.

The Findings

A total of 864 new cases of lung cancer were diagnosed during the course of the study.

Reducers (those who cut down from 15 or more cigarettes per day by at least 50%) had a 27% reduced risk of lung cancer compared to continued heavy smokers. This was a significant difference.

Continued light smokers had a 56% reduced risk of lung cancer compared to continued heavy smokers, and quitters had a 50% reduced risk compared to continued heavy smokers.

The risk of lung cancer for stable ex-smokers was 83% less than the risk among continued heavy smokers. However, stable ex-smokers still had a significantly higher risk for lung cancer compared to study participants who had never smoked.

How Does This Affect You?

This study found that heavy smokers who reduced their cigarette use by at least half significantly decreased their risk of lung cancer. But all risk is relative. Reducers only decreased their risk compared to continued heavy smokers. All smokers, even those who had quit years before, had a significantly higher risk of lung cancer than people who had never smoked.

Even the lightest smokers don’t escape the negative health effects of smoking. A study published this month in the journal Tobacco Control found that people who smoked between one and five cigarettes a day were three times as likely to die of coronary artery disease and one and a half times more likely to die of any cause than people who had never smoked. Men who smoked between one and five cigarettes a day were almost three times as likely to die of lung cancer, while women who were light smokers were almost five times more likely to die of lung cancer than their counterparts who had never smoked.

Taken together, these studies reinforce three clear messages: 1) if you don’t smoke, don’t start; 2) if you can quit, do so; 3) if you are unable to quit, cut down.

If you’d like to quit, the American Cancer Society might be a good place to start. Learn more about the benefits of quitting, strategies to overcome nicotine addiction, and support groups available to help at:

http://www.cancer.org/docroot/PED/ped_10_3.asp?sitearea=PED