News & Views
Quitting Still Best Strategy for Reducing Risks of Smoking
Article first published online: 31 DEC 2008
Copyright © 2006 American Cancer Society
CA: A Cancer Journal for Clinicians
Volume 56, Issue 1, pages 3–5, January/February 2006
How to Cite
(2006), Quitting Still Best Strategy for Reducing Risks of Smoking. CA: A Cancer Journal for Clinicians, 56: 3–5. doi: 10.3322/canjclin.56.1.3
- Issue published online: 31 DEC 2008
- Article first published online: 31 DEC 2008
Smokers who are serious about reducing the health risks from their habit are better off quitting than just cutting back, two recent studies suggest. One paper, published in Tobacco Control (2005;14:315–320), finds that smoking as few as one to four cigarettes daily can significantly raise the risk of dying compared with a nonsmoker. The other report, from JAMA (2005;294:1505–1510), shows that although heavy smokers can reduce their lung cancer risk by reducing the number of cigarettes they smoke, their risk is still significantly higher than that of nonsmokers or former smokers.
The findings suggest that “harm reduction” from tobacco use remains an elusive goal.
The paper from Tobacco Control refutes the tobacco industry claim that there is no evidence that smoking only a few cigarettes per day is a significant health hazard. The study was conducted by Kjell Bjartveit, MD, PhD, MPH, Director Emeritus of Norway's National Health Screening Service, and Aage Tverdal, PhD, Professor, Senior Researcher, Norwegian Institute of Public Health. Bjartveit is a noted tobacco researcher and recipient of the American Cancer Society (ACS)'s Luther L. Terry award, which recognizes excellence in tobacco control efforts. Their study included 43,000 women and men, aged 35 to 49 years, who were followed for more than 25 years. The authors found increasing health risks with increasing numbers of daily cigarettes. But even a few cigarettes per day significantly raised the risk of dying from all causes. For ischemic heart disease, the steepest risk increase was in both sexes between zero and one to four cigarettes per day. Above this level, the slope was less pronounced. Light smoking women and men had close to three times higher risk of dying from ischemic heart disease, compared with never smokers.
The risk of dying from lung cancer was also elevated, although the level reached significance only in women. That may be due to the small number of lung cancer cases among the light smokers in the cohort. Of more than 23,000 men in the study, just 627 said they smoked one to four cigarettes daily, and of this group, only four died of lung cancer. Nevertheless, the risk of dying of lung cancer was nearly three times higher for light-smoking men than for nonsmoking men. For women, the risk was five times greater.
“This study demonstrates once again that, despite what we would wish, there is no such thing as a safe level of smoking,” said Thomas Glynn, PhD, Director of Cancer Science and Trends at the ACS.
The authors of the JAMA paper, who were led by Nina S. Godtfredsen, MD, PhD, of Copenhagen University Hospital and Hvidovre Hospital in Denmark, also say it's too soon to adopt a strategy of harm reduction through smoking less.
“More data from long-term studies of smoking reduction are warranted, but for the present, smoking cessation and not smoking reduction should still be advocated as the ultimate method of reducing harm from smoking,” they write.
Godtfredsen and her colleagues studied nearly 20,000 men and women aged 20 to 93 years who completed a physical examination and questionnaires about lifestyle, including smoking habits. The participants were followed for as many as 31 years (mean 18 years); lung cancer incidence was confirmed through the Danish National Cancer Registry.
Smoking categories included heavy smokers (15 or more grams of tobacco per day, with 1 g being equal to one cigarette), light smokers (1 to 14 g of tobacco per day), former smokers, and nonsmokers. “Reducers” were defined as heavy smokers who cut back by 50% or more over the course of the study. “Quitters” were those smokers (heavy and light) who stopped smoking during the study.
Compared with continued heavy smokers, the “reducers” did see their lung cancer risk drop. But this drop was not proportionate to their smoking reduction: a mean decrease of 62% in tobacco consumption led to only a 27% reduction in lung cancer risk (hazard ratio [HR] 0.73). Light smokers had a 56% lower risk of lung cancer than heavy smokers (HR 0.44), and the quitters (heavy and light smokers who quit during the study) had a 50% lower risk (HR 0.50).
Former smokers had an 83% reduction in lung cancer risk (HR 0.17) compared with the heavy smokers. But even that figure was significantly higher than the risk for nonsmokers (HR 0.09).
Furthermore, the risks of heart disease and lung diseases other than cancer were not reduced by smoking less.
Those findings are important, said Glynn, because new restrictions on public smoking have led many smokers to cut back on how much they smoke.
“By doing so, they often feel that they are sharply reducing or eliminating the health dangers from smoking, but this study shows that this is not the case,” he said.
“Reducing smoking can reduce lung cancer risk somewhat, but that risk remains high. And even with reduced cigarette consumption, the risk of heart disease and [other] lung disease remains the same.”
“Compensatory” smoking is likely the reason why cutting back on cigarettes doesn't have a more positive effect on health, Glynn said. Even when they smoke less, smokers may unconsciously inhale more deeply or smoke the cigarette closer to the filter—and that keeps the level of carcinogens they ingest high.
“Fortunately, smokers now have a variety of medications and programs they can use to help them stop smoking, including the ACS's telephone Quitline, which is available at 1-877-YES-QUIT (1-877-937-7848),” Glynn noted.