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Cigarette Smoking: Health Risks and How to Quit (PDQ®)

  • Last Modified: 04/04/2014

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Summary of Evidence

Effects of Smoking Cessation
Counseling and Smoking Cessation
Physician Advice and Smoking Cessation
Drug Treatment and Smoking Cessation

Note: A separate PDQ summary on Levels of Evidence for Cancer Screening and Prevention Studies is also available.

The cancer prevention summaries in PDQ refer to cancer prevention, defined as a reduction in the incidence of cancer. The PDQ includes summaries generally classified by histological type of cancer, especially when there are known risk factors for the specific types of cancer. This summary addresses a specific risk factor, tobacco use, which is associated with a large number of different cancers (and other chronic diseases) and unequivocally contains human carcinogens.[1] The focus of this summary is on clinical interventions by health professionals that decrease the use of tobacco.

Effects of Smoking Cessation

Based on solid evidence, cigarette smoking causes cancers of the lung, oral cavity and pharynx, larynx, esophagus, bladder, kidney, pancreas, stomach, uterine cervix, and acute myeloid leukemia.[2] Smoking avoidance and smoking cessation result in decreased incidence and mortality from cancer.

Description of the Evidence

  • Study Design: Evidence obtained from a randomized controlled trial.
  • Internal Validity: Good.
  • Consistency: Good.
  • Magnitude of Effects on Health Outcomes: The relative risk (RR) of several cancers is much greater in cigarette smokers compared with nonsmokers (depending on the anatomical site of the cancer and the intensity and duration of smoking, the RR can range from twofold to tenfold or greater in smoking populations). A reduction of 15% is seen in the RR of all-cause mortality in heavy smokers subjected to intensive clinical cessation interventions.
  • External Validity: Good.
Counseling and Smoking Cessation

Based on solid evidence, counseling by a health professional improves smoking cessation rates.

Description of the Evidence

  • Study Design: Evidence obtained from randomized controlled trials.
  • Internal Validity: Good.
  • Consistency: Good.
  • Magnitude of Effects on Health Outcomes: Counseling improves cessation rates (odds ratio [OR], 1.56; 95% confidence interval [CI], 1.32–1.84).[3,4]
  • External Validity: Good.
Physician Advice and Smoking Cessation

Based on solid evidence, simple advice from a physician to stop smoking improves smoking cessation rates.

  • Study Design: Evidence obtained from randomized controlled trials.
  • Internal Validity: Good.
  • Consistency: Good.
  • Magnitude of Effects on Health Outcomes: Physician advice improves cessation rates (relative risk [RR], 1.66; 95% CI, 1.42–1.94).[3]
  • External Validity: Good.
Drug Treatment and Smoking Cessation

Based on solid evidence, drug treatments, including nicotine replacement therapies (gum, patch, spray, lozenge, and inhaler), selected antidepressant therapies (e.g., bupropion), and nicotinic receptor agonist therapy (varenicline), result in better smoking cessation rates than placebo.

Description of the Evidence

  • Study Design: Evidence obtained from randomized controlled trials.
  • Internal Validity: Good.
  • Consistency: Good.
  • Magnitude of Effects on Health Outcomes: Nicotine replacement therapy treatments, alone or in combination, improve cessation rates over placebo after 6 months (RR, 1.58; 95% CI, 1.50–1.66).[5] Treatment with bupropion improves cessation rates over placebo after 6 months (OR, 1.94; 95% CI, 1.72–2.19).[6] Varenicline therapy treatment improves cessation rates over placebo after 6 months (RR, 2.33; 95% CI, 1.95–2.80).[7]
  • External Validity: Good.
References
  1. IARC Working Group on the Evaluation of Carcinogenic Risks to Humans: Tobacco smoke and involuntary smoking. IARC Monogr Eval Carcinog Risks Hum 83: 1-1438, 2004.  [PUBMED Abstract]

  2. U.S. Department of Health and Human Services: The Health Consequences of Smoking: A Report of the Surgeon General. Atlanta, Ga: U.S. Department of Health and Human Services, CDC, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2004. Available online. Last accessed May 21, 2014. 

  3. Lancaster T, Stead L: Physician advice for smoking cessation. Cochrane Database Syst Rev (4): CD000165, 2004.  [PUBMED Abstract]

  4. Lemmens V, Oenema A, Knut IK, et al.: Effectiveness of smoking cessation interventions among adults: a systematic review of reviews. Eur J Cancer Prev 17 (6): 535-44, 2008.  [PUBMED Abstract]

  5. Silagy C, Lancaster T, Stead L, et al.: Nicotine replacement therapy for smoking cessation. Cochrane Database Syst Rev (3): CD000146, 2004.  [PUBMED Abstract]

  6. Hughes JR, Stead LF, Lancaster T: Antidepressants for smoking cessation. Cochrane Database Syst Rev (1): CD000031, 2007.  [PUBMED Abstract]

  7. Cahill K, Stead LF, Lancaster T: Nicotine receptor partial agonists for smoking cessation. Cochrane Database Syst Rev (3): CD006103, 2008.  [PUBMED Abstract]