Reading time: 6 – 9 minutes
We’ve discussed smoking and health a number of times recently:
- Smoking Cessation Timeline: What Happens When You Quit
- Irreversible Gene Expression Changes From Smoking
One of our readers asked a question I’m sure many have us have wondered about at one time or another:
Which is worse for the development of lung cancer — smoking heavily over a short period of time or smoking fewer cigarettes over many years?
Here’s what the research has to say:
In 2003, researchers at Memorial Sloan-Kettering Cancer Center created a prediction tool that can assess a long-term smoker’s absolute risk of developing lung cancer within 10 years. How long and how much people have smoked, as well as how long it’s been since their last puff, affect the risk of getting lung cancer.
The formula for the study was published in the Journal of the National Cancer Institute. I’ve linked to the full article since it’s publicly available. The study uses a number of predictors, including age, duration of smoking, average amount smoked per day while smoking and duration of abstinence from smoking (for former smokers) . These predictors are not only identifiable from a clinical history but they are established or strongly suspected risk factors for lung cancer. Additionally, they are also risk factors for all-cause mortality.
Figure 1 models multivariable relations between 1-year lung cancer risk and (A) duration of smoking, (B) average number of cigarettes smoked per day, (C) duration of abstinence and (D) age. In panel A, the relative risk of lung cancer increases exponentially with duration of smoking. In contrast, panel B shows that the relative risk of lung cancer tends to level off between 30 and 60 cigarettes smoked per day.
What does this mean? It means that the relative risk of tobacco-attributable lung cancer sharply increases with increasing duration of smoking, much more so than smoking intensity (i.e. the number of cigarettes smoked per day).
The model for the prediction tool was derived from data collected during CARET, a multicenter, randomized, controlled study that evaluated the impact of beta-carotene and vitamin A supplementation on lung cancer incidence and mortality . Unfortunately, the prediction tool only works for people age 50 and older who smoked at least 10 cigarettes a day for at least 25 years, since those were the people tracked for cancer development in the study.
Further research found that the model described above slightly underestimated the observed risk of lung cancer over 10 years . I choose to write about this particular study because of the accessibility of the online prediction tool. However, other risk models have been developed [4-6].
Additional studies have also suggested that smoking duration has a stronger effect in the prediction of lung cancer risk than number of cigarettes smoked per day [7-10]. These models are consistent with the results from epidemiologic studies, which indicate that risks of lung cancer, as well as bladder cancer, tend to level off with increased smoking intensity .
Smoking cessation at any age is beneficial. Nevertheless, lower lung cancer death risk is observed for people who quit at younger ages . Indeed, cessation of smoking prior to middle age is associated with a more than 90% reduction in cancer risk attributed to tobacco .
This isn’t to say that smoking intensity isn’t a major contributor to tobacco-attributable cancer risk. However, the take-home message is that long-term smoking clearly impacts lung cancer risk to a greater extent. That’s why it’s more important than ever to quit smoking now.
- Bach et al. Variations in lung cancer risk among smokers. J Natl Cancer Inst. 2003 Mar 19;95(6):470-8.
- Omenn et al. The beta-carotene and retinol efficacy trial (CARET) for chemoprevention of lung cancer in high risk populations: smokers and asbestos-exposed workers. Cancer Res. 1994 Apr 1;54(7 Suppl):2038s-2043s.
- Cronin et al. Validation of a model of lung cancer risk prediction among smokers. J Natl Cancer Inst. 2006 May 3;98(9):637-40.
- Peto et al. Smoking, smoking cessation, and lung cancer in the UK since 1950: combination of national statistics with two case-control studies. BMJ. 2000 Aug 5;321(7257):323-9.
- Prindiville et al. Sputum cytological atypia as a predictor of incident lung cancer in a cohort of heavy smokers with airflow obstruction. Cancer Epidemiol Biomarkers Prev. 2003 Oct;12:987-93.
- Cassidy et al. Defining high-risk individuals in a population-based molecular-epidemiological study of lung cancer. Int J Oncol. 2006 May;28(5):1295-301.
- Doll and Peto. Cigarette smoking and bronchial carcinoma: dose and time relationships among regular smokers and lifelong non-smokers. J Epidemiol Community Health. 1978 Dec;32(4):303-13.
- Peto, R Influence of dose and duration of smoking on lung cancer rates. Zaridze, D Peto, R eds. Tobacco: a major international health hazard; proceedings of an international meeting Moscow, USSR, June 4-6, 1985. 1986 World Health Organization, International Agency for Research on Cancer Lyon, France. International Agency for Research on Cancer Science Publication No. 74, 23-33.
- Flanders et al. Lung cancer mortality in relation to age, duration of smoking, and daily cigarette consumption: results from Cancer Prevention Study II. Cancer Res. 2003 Oct 1;63(19):6556-62.
- Lubin and Caporaso. Cigarette smoking and lung cancer: modeling total exposure and intensity. Cancer Epidemiol Biomarkers Prev. 2006 Mar;15(3):517-23.
- Vineis et al. Levelling-off of the risk of lung and bladder cancer in heavy smokers: an analysis based on multicentric case-control studies and a metabolic interpretation. Mutat Res. 2000 Jul;463(1):103-10.
- Halpern et al. Patterns of absolute risk of lung cancer mortality in former smokers. J Natl Cancer Inst. 1993 Mar 17;85(6):457-64.
- Peto et al. Smoking, smoking cessation, and lung cancer in the UK since 1950: combination of national statistics with two case-control studies. BMJ. 2000;321:323-329.