Smoking cessation

Smoking cessation (colloquially quitting smoking) is the process of discontinuing the practice of inhaling a smoked substance.^[1] This article focuses exclusively on cessation of tobacco smoking; however, the methods described may apply to cessation of smoking other substances that can be difficult to stop using due to the development of strong physical substance dependence or psychological dependence.

Smoking cessation can occur with or without assistance from health care professionals or the use of medications.^[2] Methods that have been found to be effective include interventions aimed at health care providers and health care systems; medications including nicotine replacement therapy (NRT) and varenicline; individual and group counseling; and Web-based and computer programs. Although stopping smoking can cause side effects such as weight gain, smoking cessation programs are cost-effective because of the positive health benefits.

• There is news about cessation: in a growing number of countries, there are more ex-smokers than smokers.^[2]
• Up to three-quarters of ex-smokers have quit without assistance (“cold turkey” or cut down then quit), and unaided cessation is by far the most common method used by most successful ex-smokers.^[2]
• A serious attempt at stopping need not involve using nicotine replacement therapy (NRT) or other drugs or getting professional support.^[2]
• Early “failure” is a normal part of trying to stop. Many initial efforts are not serious attempts.^[2]
• NRT, other prescribed pharmaceuticals, and professional counselling or support also help many smokers, but are certainly not necessary for quitting.^[2]

Nicotine addiction

Tobacco contains the chemical nicotine. Smoking cigarettes can lead to nicotine addiction.^{[3]:2300–2301} The addiction begins when nicotine acts on nicotinic acetylcholine receptors to release neurotransmitters such as dopamine, glutamate, and gamma-aminobutyric acid.^[3]:2296 Cessation of smoking leads to symptoms of nicotine withdrawal such as anxiety and irritability.^[3]:2298 Methods of smoking cessation must address nicotine addiction and nicotine withdrawal symptoms.

Methods of smoking cessation

Major reviews of the scientific literature on smoking cessation include:

• Systematic reviews of the Cochrane Tobacco Addiction Group of the Cochrane Collaboration.^[4] As of 2011, this independent, international, not-for-profit organization has published over 60 systematic reviews "on interventions to prevent and treat tobacco addiction"^[4] which will be referred to as "Cochrane reviews."
• Clinical Practice Guideline: Treating Tobacco Use and Dependence: 2008 Update of the United States Department of Health and Human Services, which will be referred to as the "2008 Guideline."^[5] The Guideline was originally published in 1996^[6] and revised in 2000.^[7] For the 2008 Guideline, experts screened over 8700 research articles published between 1975 and 2007.^[5]:13–14 More than 300 studies were used in meta-analyses of relevant treatments; an additional 600 reports were not included in meta-analyses, but helped formulate the recommendations.^[5]:22 Limitations of the 2008 Guideline include its not evaluating studies of "cold turkey" methods ("unaided quit attempts") and its focus on studies that followed up subjects only to about 6 months after the "quit date" (even though almost one-third of former smokers who relapse before one year will do so 7–12 months after the "quit date").^{[5]:19,23[8][9]}

Unassisted methods

Analyzing a 1986 U.S. survey, Fiore et al. (1990) found that 95% of former smokers who had been abstinent for 1–10 years had made an unassisted last quit attempt.^[10] The most frequent unassisted methods were "cold turkey" and "gradually decreased number" of cigarettes.^[10] A 1995 meta-analysis estimated that the quit rate from unaided methods was 7.3% after an average of 10 months of follow-up.^[11] Another estimate is that "only about 4% to 7% of people are able to quit smoking on any given attempt without medicines or other help."^[12]

Cold turkey

"Cold turkey" is abrupt cessation of all nicotine use. In three studies, it was the quitting method used by 76%,^[13] 85%,^[10] or 88%^[14] of long-term successful quitters. In a large British study of ex-smokers in the 1980s, before the advent of pharmacotherapy, 53% of the ex-smokers said that it was “not at all difficult” to stop, 27% said it was “fairly difficult”, and the remainder found it very difficult.^[2] Cold turkey methods have been advanced by J. Wayne McFarland and Elman J. Folkenburg;^[15][16] Joel Spitzer and John R. Polito;^[17] and Allen Carr.^[18]

Health care provider and system interventions

Interventions related to health care providers and health care systems have been shown to improve smoking cessation among people who visit those providers.

• A clinic screening system (e.g., computer prompts) to identify whether or not a person smokes doubled abstinence rates, from 3.1% to 6.4%.^[5]:78–79 Similarly, the Task Force on Community Preventive Services determined that provider reminders alone or with provider education are effective in promoting smoking cessation.^[19]:33–38
• A 2008 Guideline meta-analysis estimated that physician advice to quit smoking led to a quit rate of 10.2%, as opposed to a quit rate of 7.9% among patients who did not receive physician advice to quit smoking.^[5]:82–83 A Cochrane review found that even brief advice from physicians had "a small effect on cessation rates."^[20] However, one study from Ireland involving vignettes found that physicians' probability of giving smoking cessation advice declines with the patient's age,^[21] and another study from the U.S. found that only 81% of smokers age 50 or greater received advice on quitting from their physicians in the preceding year.^[22]
• For person-to-person counseling sessions, the duration of each session, the total amount of contact time, and the number of sessions all correlated with the effectiveness of smoking cessation. For example, "Higher intensity counseling (>10 minutes)" produced a quit rate of 22.1% as opposed to 10.9% for "no contact"; over 300 minutes of contact time produced a quit rate of 25.5% as opposed to 11.0% for "no minutes"; and more than 8 sessions produced a quit rate of 24.7% as opposed to 12.4% for 0–1 sessions.^[5]:83–86
• Both physicians and nonphysicians increased abstinence rates compared with self-help or no clinicians.^[5]:87–88 For example, a Cochrane review of 31 studies found that nursing interventions increased the likelihood of quitting by 28%.^[23]
• According to the 2008 Guideline, based on two studies the training of clinicians in smoking cessation methods may increase abstinence rates^[5]:130; however, a Cochrane review found "no strong evidence" that such training decreased smoking in patients.^[24]
• Reducing or eliminating the costs of cessation therapies for smokers increased quit rates in three meta-analyses.^{[5]:139–140[19]:38–40[25]}
• In one systematic review and meta-analysis, multi-component interventions increased quit rates in primary care settings.^[26] "Multi-component" interventions were defined as those that combined two or more of the following strategies known as the "5 A's"^[5]:38–43:
  • Ask — Systematically identify all tobacco users at every visit
  • Advise — Strongly urge all tobacco users to quit
  • Assess — Determine willingness to make a quit attempt
  • Assist — Aid the patient in quitting (provide counseling and medication)
  • Arrange — Ensure followup contact

Biochemical feedback

Various methods exist that allow a smoker to see the impact of their tobacco use, and the immediate effects of quitting. Using biochemical feedback methods can allow tobacco-users to be identified and assessed, and the use of monitoring throughout an effort to quit can increase motivation to quit.^[27][28]

• Breath carbon monoxide (CO) monitoring: Because carbon monoxide is a significant component of cigarette smoke, a breath carbon monoxide monitor can be used to detect recent cigarette use. Carbon monoxide concentration in breath has been shown to be directly correlated with the CO concentration in blood, known as percent carboxyhemoglobin. The value of demonstrating blood CO concentration to a smoker through a non-invasive breath sample is that it links the smoking habit with the physiological harm associated with smoking. ^[29] Within hours of quitting, CO concentrations show a noticeable decrease, and this can be encouraging for someone working to quit. Breath CO monitoring has been utilized in smoking cessation as a tool to provide patients with biomarker feedback, similar to the way in which other diagnostic tools such as the stethoscope, the blood pressure cuff, and the cholesterol test have been used by treatment professionals in medicine. ^[27]
• Cotinine: A metabolite of nicotine, cotinine is present in smokers. Like carbon monoxide, a cotinine test can serve as a reliable biomarker to determine smoking status.^[30] Cotinine levels can be tested through urine, saliva, blood, or hair samples, with one of the main concerns of cotinine testing being the invasiveness of typical sampling methods.

While both measures offer high sensitivity and specificity, they differ in usage method and cost. As an example, breath CO monitoring is non-invasive, while cotinine testing relies on a bodily fluid. These two methods can be used either alone or together, for example, in a situation where abstinence verification needs additional confirmation.^[31]

Single medications

The American Cancer Society estimates that "between about 25% and 33% of smokers who use medicines can stay smoke-free for over 6 months."^[12] Single medications include:

• Nicotine replacement therapy (NRT): Five medications approved by the U.S. Food and Drug Administration (FDA) deliver nicotine in a form that does not involve the risks of smoking. The five NRT medications, which in a Cochrane review increased the chances of stopping smoking by 50 to 70% compared to placebo or to no treatment,^[32] are:
  1. transdermal nicotine patches deliver doses of the addictive chemical nicotine, thus reducing the unpleasant effects of nicotine withdrawal. These patches can give smaller and smaller doses of nicotine, slowly reducing dependence upon nicotine and thus tobacco. A Cochrane review found further increased chance of success in a combination of the nicotine patch and a faster acting form.^[32] Also, this method becomes most effective when combined with other medication and psychological support.^[33]
  2. gum
  3. lozenges
  4. sprays
  5. inhalers.

A study found that 93 percent of over-the-counter NRT users relapse and return to smoking within six months.^[34]

• Antidepressant: Bupropion is FDA-approved and is marketed under the brand name Zyban. Bupropion is contraindicated in epilepsy, seizure disorder; anorexia/bulimia (eating disorders), patients' use of antidepressant drugs (MAO inhibitors) within 14 days, patients undergoing abrupt discontinuation of ethanol or sedatives (including benzodiazepines such as Valium).^[35][36]
• Nicotinic receptor partial agonists:
  • Cytisine (Tabex) is a plant extract that has been in use since the 1960s in former Soviet-bloc countries.^[37] It was the first medication approved as an aid to smoking cessation, and has very few side effects in small doses.^[38][39]:70
  • Varenicline tartrate is a prescription drug marketed by Pfizer as Chantix in the U.S. (under FDA approval) and as Champix outside the U.S.^[40] Synthesized as an improvement upon cytisine,^[41] varenicline decreases the urge to smoke and reduces withdrawal symptoms.^[42] Two systematic reviews and meta-analyses supported by unrestricted funding from Pfizer, one in 2006^[43] and one in 2009,^[44] found varenicline more effective than NRT or bupropion. A table in the 2008 Guideline indicates that 2 mg/day of varenicline leads to the highest abstinence rate (33.2%) of any single therapy, while 1 mg/day leads to an abstinence rate of 25.4%.^[5]:109 A 2011 Cochrane review of 15 studies (13 of which had been sponsored by Pfizer) found that varenicline was significantly superior to bupropion at one year but that varenicline and nicotine patches produced the same level of abstinence at 24 weeks.^[45] A 2011 review of double-blind studies found that varenicline has increased risk of serious adverse cardiovascular events compared with placebo.^[46] Varenicline may cause neuropsychiatric side effects; for example, in 2008 the U.K. Medicines and Healthcare products Regulatory Agency issued a warning about possible suicidal thoughts and suicidal behavior associated with varenicline.^[47]

• Moclobemide has been tested in heavy dependent smokers against placebo based on the theory that tobacco smoking could be a form of self medicating of major depression,^[48] and moclobemide could therefore help increase abstinence rates due to moclobemide mimicking the MAO-A inhibiting effects of tobacco smoke. Moclobemide was administered for 3 months and then stopped; at 6 months follow-up it was found those who had taken moclobemide for 3 months had a much higher successful quit rate than those in the placebo group. However, at 12 month follow-up the difference between the placebo group and the moclobemide group was no longer significant.^[49]

Two other medications have been used in trials for smoking cessation, although they are not approved by the FDA for this purpose. They may be used under careful physician supervision if the first line medications are contraindicated for the patient.

1. Clonidine may reduce withdrawal symptoms and "approximately doubles abstinence rates when compared to a placebo," but its side effects include dry mouth and sedation, and abruptly stopping the drug can cause high blood pressure and other side effects.^{[5]:55,116–117[50]}
2. Nortriptyline, another antidepressant, has similar success rates to bupropion but has side effects including dry mouth and sedation.^{[5]:56,117–118[36]}

Combinations of medications

The 2008 Guideline specifies that three combinations of medications are effective^{[5]:118–120}:

• Long-term nicotine patch and ad libitum NRT gum or spray
• Nicotine patch and nicotine inhaler
• Nicotine patch and bupropion (the only combination that the FDA has approved for smoking cessation)

Cut down to quit

Gradual reduction involves slowly reducing one's daily intake of nicotine. This can be done in four ways: (a) by repeated changes to cigarettes with lower levels of nicotine, (b) by gradually reducing the number of cigarettes smoked each day, (c) by smoking only a fraction of a cigarette each time lighting up, or (d) applying NicoBloc drops on the cigarette filter which absorbs up to 99% of tar and nicotine. A 2009 systematic review by researchers at the University of Birmingham found that gradual nicotine replacement therapy was effective in smoking cessation.^[51][52] A 2010 Cochrane review found that abrupt cessation and gradual reduction with pre-quit NRT produced similar quit rates whether or not pharmacotherapy or counseling was used. ^[53][54]

Community interventions

A Cochrane review concluded that there was "limited evidence" that community interventions using "multiple channels to provide reinforcement, support and norms for not smoking" had an effect on smoking cessation among adults.^[55] Specific methods used in the community to encourage smoking cessation among adults include:

• Policies making workplaces^[13] and public places smoke-free. It is estimated that "comprehensive clean indoor laws" can increase smoking cessation rates by 12%–38%.^[56]
• Voluntary rules making homes smoke-free, which are thought to promote smoking cessation.^[13][57]
• Initiatives to educate the public regarding the health effects of secondhand smoke
• Increasing the price of tobacco products, for example by taxation. The Task Force on Community Preventive Services found "strong scientific evidence" that this is effective in increasing tobacco use cessation.^[19]:28–30 It is estimated that an increase in price of 10% will increase smoking cessation rates by 3–5%.^[56]
• Mass media campaigns. The Task Force on Community Preventive Services declared that "strong scientific evidence" existed for these when "combined with other interventions"^[19]:30–32, but a Cochrane review concluded that it was "difficult to establish their independent role and value".^[58]

Competitions and incentives

One 2008 Cochrane review concluded that "incentives and competitions have not been shown to enhance long-term cessation rates."^[59] However, a randomized trial published in 2009 found that financial incentives for smoking cessation led to significantly higher rates of smoking cessation 15–18 months after enrollment.^[60] Furthermore, a different 2008 Cochrane review found that one type of competition, "Quit and Win," did increase quit rates among participants.^[61]

Psychosocial approaches

• Great American Smokeout is an annual event that invites smokers to quit for one day, hoping they will be able to extend this forever.
• The World Health Organization's World No Tobacco Day is held on May 31 each year.
• Smoking-cessation support and counseling is often offered over the internet, over phone quitlines^[62][63] (e.g., the US toll-free number 1-800-QUIT-NOW), or in person. Three meta-analyses have concluded that telephone cessation counseling is effective when compared with minimal or no counseling or self-help, and that telephone cessation counseling with medication is more effective than medication alone.^{[5]:91–92[19]:40–42[64]}
• Group or individual counseling can help people who want to quit. Counseling is effective alone; counseling and medication is more effective than medication alone (and conversely, medication and counseling is more effective than counseling alone); and the number of sessions of counseling with medication correlates with effectiveness.^{[5]:89–90,101–103[65][66]} The types of counseling that have been effective in smoking cessation programs include motivational interviewing^[67][68][69] and cognitive behavioral therapy.^[70]
• Multiple formats of psychosocial interventions increase quit rates: 10.8% for no intervention, 15.1% for one format, 18.5% for 2 formats, and 23.2% for three or four formats.^[5]:91
• The Transtheoretical Model including "stages of change" has been used in tailoring smoking cessation methods to individuals.^{[71][72][73][74]} However, a 2010 Cochrane review concluded that "stage-based self-help interventions (expert systems and/or tailored materials) and individual counselling were neither more nor less effective than their non-stage-based equivalents."^[75]

Self-help

A 2005 Cochrane review found that self-help materials may produce only a small increase in quit rates.^[76] In the 2008 Guideline, "the effect of self-help was weak," and the number of types of self-help did not produce higher abstinence rates.^[5]:89–91 Nevertheless, self-help modalities for smoking cessation include:

• In-person self-help groups such as Nicotine Anonymous^[77][78] or electronic self-help groups such as Stomp It Out.^[79]
• Newsgroups: The Usenet group alt.support.stop-smoking has been used by people quitting smoking as a place to go to for support from others.^[80] It is accessible through Google Groups.^[81]
• Interactive web- and computer-based programs that assist participants in quitting. For example, "quit meters" keep track of statistics such as how long a person has remained abstinent.^[82] In the 2008 Guideline, there was no meta-analysis of computerized interventions, but they were described as "highly promising."^[5]:93–94 A meta-analysis published in 2009,^[83] a Cochrane review published in 2010,^[84] and a 2011 systematic review^[85] found the evidence base for such interventions weak.
• Mobile phone-based interventions: A 2009 Cochrane review stated that "more evidence is needed" to determine the effectiveness of such interventions.^[86] As of 2009, a randomized trial of mobile phone-based smoking cessation support was underway in the U.K.^[87]
• Self-help books such as Allen Carr's Easy Way to Stop Smoking.^[18]
• Spirituality: In one survey of adult smokers, 88% reported a history of spiritual practice or belief, and of those more than three-quarters were of the opinion that using spiritual resources may help them quit smoking.^[88]

Substitutes for cigarettes

• Electronic cigarette: Shaped like a cigar or cigarette to satisfy habitual tactile cravings, this device contains a rechargeable battery and a heating element that vaporizes liquid nicotine (and other flavorings) from an insertable cartridge, at lower initial cost than a vaporizer but with similar advantages including significantly reducing tar and carbon monoxide. In September 2008, the World Health Organization issued a release proclaiming that it does not consider the electronic cigarette to be a legitimate smoking cessation aid, stating that to its knowledge, "no rigorous, peer-reviewed studies have been conducted showing that the electronic cigarette is a safe and effective nicotine replacement therapy."^[89]
• The National Institute of Health recommends chewing cinnamon sticks when trying to quit the use of tobacco. In addition to raw cinnamon sticks, cinnamon flavored toothpicks are used to help curb the urge for tobacco.^[90][91]
• Plastic cigarette substitute: In one 2006 study, giving people a free "Better Quit" hollow tube resembling a cigarette did not improve quit rates.^[92]

Alternative approaches

• Acupuncture. A Cochrane review concludes that acupuncture "do[es] not appear to help smokers who are trying to quit",^[93] a meta-analysis from the 2008 Guideline showed no difference between acupuncture and placebo^[5]:99–100, and the 2008 Guideline found no scientific studies supporting laser therapy based on acupuncture principles but without the needles.^[5]:99. Nevertheless, acupuncture has been called a "reasonable option" for smoking cessation because of its low risk.^[94]
• Aromatherapy. A 2006 book reviewing the scientific literature on aromatherapy^[95] identified only one study on smoking cessation and aromatherapy; the study concerned black pepper oil.^[96]
• Hypnosis. Clinical trials studying hypnosis and hypnotherapy as a method for smoking cessation have been inconclusive^[5]:100;^[97] however, a randomized trial published in 2008 found that hypnosis and nicotine patches "compares favorably" with standard behavioral counseling and nicotine patches in 12-month quit rates.^[98]
• Herbs. Many herbs have been studied as a method for smoking cessation including lobelia and St John's wort^[99][100]. St. John's Wort is effective at treating mild to moderate depression and shares biosimilar properties to the FDA approved drug bupropion, sold under the brand name Zyban, approved for smoking cessation. The results of the study were inconclusive but St. Johns Wort showed few adverse events. Lobelia has been used to treat respiratory diseases like asthma and bronchitis, and has been used for smoking cessation because of chemical similarities to tobacco, but lobelia is now listed in the FDA's Poisonous Plant Database^[101][102]. Lobelia can still be found in many products sold for smoking cessation and should be used with caution, although there are effective herbal smoking cessation aids that do not contain lobelia.

Smoking cessation in special populations

Children and adolescents

Methods used with children and adolescents include:

• Motivational enhancement^[103]
• Psychological support^[103]
• Youth anti-tobacco activities, such as sport involvement
• School-based curricula, such as life-skills training
• Access reduction to tobacco
• Anti-tobacco media
• Family communication

A Cochrane review, mainly of studies combining motivational enhancement and psychological support, concluded that "complex approaches" for smoking cessation among young people show promise.^[103] The 2008 Guideline recommends counseling for adolescent smokers on the basis of a meta-analysis of seven studies.^{[5]:159–161} Neither the Cochrane review nor the 2008 Guideline recommends medications for adolescents who smoke.

Pregnant women

Smoking during pregnancy can cause adverse health effects in both the woman and the foetus. The 2008 Guideline determined that "person-to-person psychosocial interventions" (typically including "intensive counseling") increased abstinence rates in pregnant women who smoke to 13.3%, compared with 7.6% in usual care.^{[5]:165–167}

Workers

A 2008 Cochrane review of smoking cessation programs in workplaces concluded that "interventions directed towards individual smokers increase the likelihood of quitting smoking."^[104] A 2010 systematic review determined that worksite incentives and competitions needed to be combined with additional interventions to produce significant increases in smoking cessation rates.^[105]

Hospitalized smokers

People who smoke who are hospitalized may be particularly motivated to quit.^{[5]:149–150} A 2007 Cochrane review found that interventions beginning during a hospital stay and continuing for one month or more after discharge were effective in producing abstinence.^[106]

Comparison of success rates

Comparison of success rates across interventions can be difficult because of different definitions of "success" across studies.^[12] Robert West and Saul Shiffman have authored works on smoking cessation. They believe that, used together, "behavioral support" and "medication" can quadruple the chances that a quit attempt will be successful. Both, however, disclosed that they are paid researchers or consultants to pharmaceutical companies or manufacturers of smoking cessation medications.^{[39]:73,76,80}

In 2010 the National Tobacco Cessation Collaborative (NTCC) created "What Works to Quit: A Guide to Quit Smoking Methods" which compares the efficacy and cost of 17 smoking cessation methods.^[107] The guide, based on the 2008 Guideline, reports that smokers using a combination method of pharmacological and psychosocial approaches have the most success compared to those who use pharmaceutical or psychosocial approaches in isolation.^[107]

A 2008 systematic review in the European Journal of Cancer Prevention found that group behavioral therapy was the most effective intervention strategy for smoking cessation, followed by bupropion, intensive physician advice, nicotine replacement therapy, individual counseling, telephone counseling, nursing interventions, and tailored self-help interventions; the study did not discuss varenicline.^[56]

Factors affecting success

Quitting can be harder for individuals with dark pigmented skin compared to individuals with pale skin since nicotine has an affinity for melanin-containing tissues. Studies suggest this can cause the phenomenon of increased nicotine dependence and lower smoking cessation rate in darker pigmented individuals.^[109]

There is an important social component to smoking. A 2008 study analyzing a densely interconnected network of over 12,000 individuals found that smoking cessation by any given individual reduced the chances of others around them lighting up by the following amounts: a spouse by 67%, a sibling by 25%, a friend by 36%, and a coworker by 34%.^[110] Nevertheless, a Cochrane review determined that interventions to increase social support for a smoker's cessation program did not increase long-term quit rates.^[111]

Smokers with major depressive disorder are less successful at quitting smoking than non-depressed smokers.^[5]:81[112]

Relapse (resuming smoking after quitting) has been related to psychological issues such as low self-efficacy^[113] or non-optimal coping responses;^[114] however, psychological approaches to prevent relapse have not been proven to be successful.^[115] In contrast, varenicline may help some relapsed smokers.^[115]

Side effects

Symptoms

In a 2007 review of the effects of abstinence from tobacco, Hughes concluded that "anger, anxiety, depression, difficulty concentrating, impatience, insomnia, and restlessness are valid withdrawal symptoms that peak within the first week and last 2–4 weeks."^[36] In contrast, "constipation, cough, dizziness, increased dreaming, and mouth ulcers" may or may not be symptoms of withdrawal, while drowsiness, fatigue, and certain physical symptoms ("dry mouth, flu symptoms, headaches, heart racing, skin rash, sweating, tremor") were not symptoms of withdrawal.^[36]

Weight gain

People who successfully quit smoking may gain weight. In a 1991 study that found that the mean weight gain due to smoking cessation was 2.8 kg (6.2 lb) for men and 3.8 kg (8.4 lb) for women, the researchers concluded "weight gain is not likely to negate the health benefits of smoking cessation, but its cosmetic effects may interfere with attempts to quit."^[117]

The causes of the weight gain are unclear, but hypotheses include:

• Smoking over expresses the gene AZGP1 which stimulates lipolysis, so smoking cessation may decrease lipolysis.^[118]
• Smoking suppresses appetite, which may be caused by nicotine's effect on central autonomic neurons (e.g., via regulation of melanin concentrating hormone neurons in the hypothalamus).^[119]
• Heavy smokers are reported to burn 200 calories per day more than non-smokers eating the same diet.^[120] Possible reasons for this phenomenon include nicotine's ability to increase energy metabolism or nicotine's effect on peripheral neurons.^[119]

The 2008 Guideline suggests that sustained-release bupropion, nicotine gum, and nicotine lozenge be used "to delay weight gain after quitting."^{[5]:173–176} However, a 2009 Cochrane review concluded that "The data are not sufficient to make strong clinical recommendations for effective programmes" for preventing weight gain.^[121]

Depression

When people with a history of depression stop smoking, depressive symptoms or actual depression may result.^[112][122] This side effect of smoking cessation may be particularly common in women, as depression is more common among women than among men.^[123]

Health benefits

Many of tobacco's health effects can be minimized through smoking cessation. The health benefits over time of stopping smoking include^[124]:

• Within 20 minutes after quitting, blood pressure and heart rate decrease
• Within 12 hours, carbon monoxide levels in the blood decrease to normal
• Within 48 hours, nerve endings and sense of smell and taste both start recovering
• Within 3 months, circulation and lung function improve
• Within 9 months, there are decreases in cough and shortness of breath
• Within 1 year, the risk of coronary heart disease is cut in half
• Within 5 years, the risk of stroke falls to the same as a non-smoker, and the risks of many cancers (mouth, throat, esophagus, bladder, cervix) decrease significantly
• Within 10 years, the risk of dying from lung cancer is cut in half,^[125] and the risks of larynx and pancreas cancers decrease
• Within 15 years, the risk of coronary heart disease drops to the level of a non-smoker

The British doctors study showed that those who stopped smoking before they reached 30 years of age lived almost as long as those who never smoked.^[126] Stopping in one's sixties can still add three years of healthy life.^[126] A randomized trial from the U.S. and Canada showed that a smoking cessation program lasting 10 weeks decreased mortality from all causes over 14 years later.^[127]

Another published study, “Smoking Cessation Reduces Postoperative Complications: A Systematic Review and Meta-analysis,” examined six randomized trials and 15 observational studies to look at the effects of preoperative smoking cessation on postoperative complications. The findings were: 1) taken together, the studies demonstrated decreased likelihood of postoperative complications in patients who ceased smoking prior to surgery; 2) overall, each week of cessation prior to surgery increased the magnitude of the effect by 19%. A significant positive effect was noted in trials where smoking cessation occurred at least four weeks prior to surgery; 3) For the six randomized trials, they demonstrated on average a relative risk reduction of 41% for postoperative complications.^[128]

Cost-effectiveness

Cost-effectiveness analyses of smoking cessation programs have shown that they increase quality-adjusted life years (QALYs) at costs comparable with other types of interventions to treat and prevent disease.^{[5]:134–137} Studies of the cost-effectiveness of smoking cessation include:

• In a 1997 U.S. analysis, the estimated cost per QALY varied by the type of program, ranging from group intensive counseling without nicotine replacement at $1108 per QALY to minimal counseling with nicotine gum at $4542 per QALY.^[129]
• A study from Erasmus University Rotterdam limited to people with chronic obstructive pulmonary disease found that the cost-effectiveness of minimal counseling, intensive counseling, and drug therapy were €16,900, €8,200, and €2,400 per QALY gained respectively.^[130]
• Among National Health Service smoking cessation clients in Glasgow, pharmacy one-to-one counseling cost £2,600 per QALY gained and group support cost £4,800 per QALY gained.^[131]

Statistical trends

The frequency of smoking cessation among smokers varies across countries. Smoking cessation increased in Spain between 1965 and 2000,^[132] in Scotland between 1998 and 2007,^[133] and in Italy after 2000.^[134] In contrast, in the U.S. the cessation rate was "stable (or varied little)" between 1998 and 2008,^[135] and in China smoking cessation rates declined between 1998 and 2003.^[136]

Nevertheless, in a growing number of countries there are now more ex-smokers than smokers.^[2] For example, in the U.S. as of 2010, there were 47 million ex-smokers and 46 million smokers.^[137]

See also