Highlight HEALTH

Today, the American Cancer Society (ACS) celebrates the Great American Smokeout, an annual event in the U.S. to encourage Americans to quit smoking. According to the U.S. Centers for Disease Control and Prevention (CDC), in 2006 one in five U.S. adults smoked [1]. The Great American Smokeout challenges those people to smoke less or quit smoking for the day. The event also raises awareness of the many effective ways to quit for good.

The ACS has just wrapped up their first ever video contest on YouTube, where they asked people to create videos - one minute or less - to discourage smoking. You can check out the contest winners at the American Cancer Society.

You can also read more about the harmful effects of smoking and tobacco smoke in these articles here at Highlight HEALTH:

• Smoking Duration vs. Intensity and the Impact on Lung Cancer Risk
• Irreversible Gene Expression Changes From Smoking
• Smoking Cessation Timeline: What Happens When You Quit
• Second-hand Smoke Exposure Linked to Psychological Problems in Children

Accept the Great American Smokeout Challenge.
Quit for one day, or quit for good.

References

1. Cigarette smoking among adults–United States, 2006. Centers for Disease Control and Prevention (CDC). MMWR Morb Mortal Wkly Rep. 2007 Nov 9;56(44):1157-61.
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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

Ian Gibson 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?

My answer slowly evolved from a comment to a post of its own. 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) [1]. 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 [2]. 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 [3]. 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 [11].

Smoking cessation at any age is beneficial. Nevertheless, lower lung cancer death risk is observed for people who quit at younger ages [12]. Indeed, cessation of smoking prior to middle age is associated with a more than 90% reduction in cancer risk attributed to tobacco [13].

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.

Did you ever smoke? How long were you a smoker? At what age did you quit?

References

1. Bach et al. Variations in lung cancer risk among smokers. J Natl Cancer Inst. 2003 Mar 19;95(6):470-8.
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2. 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.
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3. 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.
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4. 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.
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5. 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.
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6. 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.
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7. 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.
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8. 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.
9. 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.
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10. Lubin and Caporaso. Cigarette smoking and lung cancer: modeling total exposure and intensity. Cancer Epidemiol Biomarkers Prev. 2006 Mar;15(3):517-23.
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11. 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.
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12. 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.
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13. 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.
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In the U.S., one-quarter of adults 18 years of age and older smoke cigarettes [1]. Smoking is truly a deadly habit. With about 4000 known chemicals in tobacco smoke, more than 50 of them are known to cause cancer. According to the World Health Organization, every six seconds someone in the world dies from tobacco use [2].

How’s this for bad odds: tobacco kills 50% of its regular users. One out of every two regular smokers will die from smoking [2].

In addition, an estimated 200,000 people die every year due to second-hand smoke exposure at work. The United States Environmental Protection Agency estimates that second-hand smoke is responsible for approximately 3000 lung cancer deaths annually among non-smokers [2]. Additionally, new research has linked second-hand smoke exposure to psychological problems in children, including attention deficit disorder (ADHD) and conduct disorder.

The best time to quit smoking is RIGHT NOW. And while quitting is tough, you can start counting the benefits of not smoking in as little as 20 minutes. Here’s what happens to your body when you quit smoking [3-5]:

Why is it so difficult to quit smoking?

In one word … nicotine.

Nicotine is an organic compound known as an alkoloid (meaning a nitrogen-containing ring compound, usually water-insoluble and alcohol soluble) found in the leaves of several species of plants, predominantly tobacco, as well as in lower quantities in several frequently consumed vegetables from the nightshade or Solanaceae family, including tomatoes, potatoes, aubergines (eggplant) and peppers [6]. Nicotine by itself is not carcinogenic [7]. However, it does inhibit UV-induced activation of cell death (a process known as apoptosis) [8], interfering with the body’s ability to destroy potentially cancerous cells.

Nicotine activates a specific type of neurotransmitter receptor - the acetylcholine receptor - an integral membrane protein widely distributed in the brain and neuromuscular junctions that normally responds to the binding of the neurotransmitter acetylcholine. This is nicotine’s addictive property: activation of acetylcholine receptors leads to an increased flow of adrenaline (epinephrine), which increases the heart rate, blood pressure, respiration and glucose levels in the blood.

When smokers try to cut back or quit smoking, they experience nicotine withdrawal. A regular smoker will have nicotine or its by-products present in their body for 3 to 4 days after quitting [9]. Withdrawal symptoms appear within a few hours and peak 24 to 48 hours after quitting [10]. Withdrawal symptoms include tobacco craving, a desire for sweets, increased coughing and impaired performance on tasks that require concentration [10-11]. Most symptoms last an average of one month, but hunger (due to the lack of increased blood glucose) and craving can last 6 months or more [10].

Did you ever smoke? How hard was it for you to quit? How did you do it?

References

1. 2005 National Survey on Drug Use & Health Results. U.S. Department of Health and Human Services. Substance Abuse and Mental Health Services Administration. Office of Applied Studies. 2005.
2. 10 Facts About Tobacco and Second-hand Smoke. World Health Organization.
3. Quitting Smoking: Why To Quit and How To Get Help. National Cancer Institute.
4. Quit Smoking - Smoking Cessation Support - Benefits. American Lung Association.
5. When Smokers Quit - The Health Benefits Over Time. American Cancer Society. Revised 10/25/2006.
6. Siegmund et al. Determination of the nicotine content of various edible nightshades (Solanaceae) and their products and estimation of the associated dietary nicotine intake. J Agric Food Chem. 1999 Aug;47(8):3113-20.
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7. Dasgupta and Chellappan. Nicotine-mediated cell proliferation and angiogenesis: new twists to an old story. Cell Cycle. 2006 Oct;5(20):2324-8. Epub 2006 Oct 16.
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8. Sugano et al. Nicotine inhibits UV-induced activation of the apoptotic pathway. Toxicol Lett. 2001 Dec 15;125(1-3):61-5.
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9. Guide to Quitting Smoking. American Cancer Society. Revised 10/27/2006.
10. Hughes and Hatsumkami. The nicotine withdrawal syndrome: A brief review and update. International Journal of Smoking Cessation. 1992 1:21-26.
11. Hughes, Higgins and Hatsukami. Effects of abstinence from tobacco: a critical review, in Research Advances in Alcohol and Drug Problems, vol 10. Edited by Kozlowski LT, Annis HM, Cappell HD, Glaser FB, Goodstadt MS, Israel Y, Kalant H, Sellers EM, Vingilis ER. New York, Plenum, 1990, pp 317-398.