Quitting smoking
Everything in the library studied for it, medical and holistic together. Within each kind, what was shown to help comes first, strongest evidence first. What was tested and not shown to help stays on the list.
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Medication
Quitting smoking
Shown to raise smoking quit rates about 1.6 times over placebo, roughly 3 extra quitters per 100, and less than varenicline did.
The numbers and sources
- How common
- Common: between 1 in 100 and 1 in 10 people.
- Effect
- Bupropion raised quit rates against placebo or no drug (RR 1.60, 95% CI 1.49 to 1.72, 50 studies) [4]. In a network meta-analysis the odds ratio against control was 1.43 (95% CrI 1.26 to 1.62), which the authors put at 3 additional quitters per 100 (95% CrI 2 to 4) [5]. In a trial of 8,144 smokers, abstinence was more likely on bupropion than placebo (OR 2.07, 95% CI 1.75 to 2.45) and more likely on varenicline than bupropion (OR 1.75, 95% CI 1.52 to 2.01) [6]. Quit rates on bupropion were lower than on varenicline (RR 0.73, 95% CI 0.67 to 0.80) and similar to single-form nicotine replacement (RR 1.03, 95% CI 0.93 to 1.13) [4].
- Population
- 18,577 participants in 50 studies, mostly adults from the community or cessation clinics [4]; 14,759 participants in 71 RCTs of bupropion within a 319-trial network [5]; 8,144 smokers with and without psychiatric disorders [6].
- Sources
- [4], [5], [6]
- Caveats
- Both reviews rated the bupropion evidence high certainty. 118 of the trials in the network reported drug or tobacco industry funding [5].
Nortriptyline for quitting smoking
Shown to about double quit rates against placebo with nortriptyline in a Cochrane review of six trials.
Compared with placebo [14]; bupropion [14]
The numbers and sources
- Effect
- Nortriptyline raised smoking cessation against placebo (RR 2.03, 95% CI 1.48 to 2.78, I² 16%). Against bupropion, quit rates did not clearly differ (RR 1.30 favoring bupropion, 95% CI 0.93 to 1.82) [14].
- Population
- 975 smokers in six nortriptyline trials, within a review of 124 studies [14].
- Sources
- [14]
- Caveats
- The evidence is for nortriptyline, not amitriptyline. Nortriptyline is not approved for quitting smoking.
Quitting smoking
Shown to raise quit rates against placebo, with about 1.9 times the odds, in a Cochrane review of six small trials, with frequent dry mouth and sedation.
Compared with placebo [8]
The numbers and sources
- Effect
- The pooled odds ratio for quitting with clonidine against placebo was 1.89 (95% CI 1.30 to 2.74). Only one of the six trials was significant on its own. Dose-dependent side effects, particularly dry mouth and sedation, were frequent [8].
- Population
- Smokers in six trials, three of oral and three of patch clonidine, most with counseling [8].
- Sources
- [8]
- Caveats
- Few trials, with potential sources of bias [8]. Clonidine is not approved for quitting smoking.
Quitting smoking
Mixed results: topiramate raised quit rates at 4 to 12 weeks against placebo, but prolonged abstinence did not differ in a meta-analysis of five trials.
Compared with placebo [11]
The numbers and sources
- Effect
- Prolonged abstinence did not differ from placebo (OR 1.19, 95% CI 0.57 to 2.5). Abstinence at single time points was higher at weeks 4, 6, 8 and 12, with an OR of 2.45 (95% CI 1.37 to 4.39) at week 12 [11].
- Population
- Smokers in 5 trials [11].
- Sources
- [11]
- Caveats
- Few trials, and publication bias could not be excluded [11].
Therapies
Quitting smoking
Not shown to raise long-term quitting. Quit rates were slightly higher than with sham acupuncture in the short term, and lower than with nicotine replacement.
Compared with sham acupuncture [12]; waiting list [12]; nicotine replacement therapy [12]; psychological interventions [12]
The numbers and sources
- Effect
- Against sham, acupuncture raised short-term abstinence (RR 1.22, 95% CI 1.08 to 1.38) and not long-term abstinence (RR 1.10, 95% CI 0.86 to 1.40). Against a waiting list, long-term abstinence did not differ significantly (RR 1.79, 95% CI 0.98 to 3.28, 3 trials). Abstinence was lower with acupuncture than with nicotine replacement, and did not differ from psychological interventions. Electrostimulation did not differ from sham electrostimulation [12].
- Population
- 38 studies of adult smokers [12].
- Sources
- [12]
- Caveats
- Funnel plot asymmetry suggested that larger studies found smaller effects [12].
Quitting smoking
Not shown to raise quit rates at 6 months or more compared with other behavioral support or medication. Group hypnotherapy and group CBT gave similar quit rates.
Compared with attention-matched behavioral treatments, intensive behavioral programs, brief behavioral advice, rapid smoking, quit-smoking medication and no intervention [11]; group cognitive behavioral therapy [12]
The numbers and sources
- Effect
- Against attention-matched behavioral treatment, quit rates did not differ (RR 1.21, 95% CI 0.91 to 1.61, 6 trials, 957 people). Nor did they differ against intensive behavioral programs (RR 0.93), brief behavioral advice (RR 0.98), rapid smoking (RR 1.00) or medication (RR 1.68, 95% CI 0.88 to 3.20). One trial of 40 people favored hypnotherapy over no intervention (RR 19.00) at very low certainty. Added to other treatment, hypnotherapy raised quitting (RR 2.10, 95% CI 1.31 to 3.35, 5 trials) in studies mostly at high risk of bias [11]. In 360 smokers, continuous abstinence over 12 months was 15.0% with group hypnotherapy and 15.6% with group CBT [12].
- Population
- 1,926 smokers in 14 trials [11]. 360 smokers at two study sites [12].
- Sources
- [11], [12]
- Caveats
- Only one trial in the Cochrane review was at low risk of bias. The reviewers write that any benefit is small at most [11].
Daily life
Death from any cause after quitting
Linked to fewer deaths after quitting at every age in large cohorts, with about 90% of the excess avoided by quitting before 40. A quit-program trial lowered deaths.
Compared with people who continued to smoke [1][2]; never-smokers, with ex-smokers' excess set against continuing smokers' excess [3]; people who continued to smoke, and never smokers [4]; never smokers, by years since quitting [5]; usual care, in a randomized trial of a quit program [6]
The numbers and sources
- Effect
- Adults who quit at ages 25 to 34, 35 to 44 or 45 to 54 gained about 10, 9 and 6 years of life against those who continued to smoke. Quitting before 40 lowered the death risk of continued smoking by about 90% [1]. In British doctors, stopping at 60, 50, 40 or 30 gained about 3, 6, 9 or 10 years [2]. Women who stopped at 25 to 34 or 35 to 44 had death rates 1.05 and 1.20 times those of never-smokers, 3% and 10% of the excess in continuing smokers [3]. Across four national cohorts, former smokers had a hazard ratio of 1.3 against never smokers. Quitting for under 3 years was linked to 90% to 95% less excess risk in people under 40, and quitting for 10 years or more to survival similar to never smokers [4]. In people 60 and older, former smokers' excess mortality (RM 1.34, 95% CI 1.28 to 1.40) fell with years since quitting, and gains were seen in people 80 and older [5]. In a randomized trial, a quit program raised 5-year quitting to 21.7% against 5.4% with usual care. Deaths were 8.83 against 10.38 per 1,000 person-years (HR for usual care 1.18, 95% CI 1.02 to 1.37) [6].
- Population
- 202,248 US adults with 15,715 deaths [1]. 34,439 male British doctors followed 50 years [2]. 1.2 million UK women followed about 12 years [3]. 1.48 million adults in the US, UK, Norway and Canada with 122,697 deaths over 15 years [4]. 17 cohorts of people 60 and older in 7 countries [5]. 5,887 middle-aged smokers with mild airway obstruction, followed 14.5 years [6].
- Sources
- [1], [2], [3], [4], [5], [6]
- Caveats
- The cohorts are observational, and people who quit may differ in other ways from those who do not. Some people quit because they are already ill, which hides part of the gain in the first years. The trial's effect comes from a program that only a minority of its group used to quit, and it enrolled only people with airway obstruction [6].
Heart disease and stroke after quitting
Linked to lower heart disease and stroke risk within 5 years of quitting, with the excess falling steadily with time but staying above never smokers for 10 to 15 years.
Compared with never smokers, with former and current smokers each set against them [7]; patients with heart disease who continued to smoke [8]; people who continued to smoke, and never smokers [9]; people who continued to smoke [10]
The numbers and sources
- Effect
- In adults 60 and older, cardiovascular death had a hazard ratio of 2.07 (95% CI 1.82 to 2.36) in current smokers and 1.37 (95% CI 1.25 to 1.49) in former smokers against never smokers. The excess fell continuously with time since quitting. Heart attack and stroke followed the same pattern [7]. In people with coronary heart disease, quitting was linked to 36% lower death from any cause than continuing to smoke (RR 0.64, 95% CI 0.58 to 0.71) [8]. In heavy smokers, quitting within 5 years was linked to lower cardiovascular disease (HR 0.61, 95% CI 0.49 to 0.76) than continuing. Against never smokers, the excess stopped being significant 10 to 15 years after quitting (HR 1.25, 95% CI 0.98 to 1.60) [9]. In adults without diabetes, recent quitters (HR 0.47) and long-term quitters (HR 0.46, 95% CI 0.34 to 0.63) had fewer cardiovascular events than smokers [10].
- Population
- 503,905 adults 60 and older in 25 cohorts, with 37,952 cardiovascular deaths [7]. 20 cohorts of patients with coronary heart disease [8]. 8,770 Framingham participants followed a median 26.4 years, 2,371 of them heavy smokers [9]. 3,251 Framingham Offspring participants followed a mean 25 years [10].
- Sources
- [7], [8], [9], [10]
- Caveats
- Observational. Many cohorts did not fully control confounding or check smoking status, though restricting to higher-quality studies changed little [8]. In people with diabetes, the estimates were similar but not significant [10].
Lung cancer after quitting
Linked to steadily lower lung cancer risk with each year after quitting in pooled cohorts, with about a fifth of the excess remaining 20 years on.
Compared with current smokers, as each review defined its reference [11][12]; people who continued to smoke, and never smokers [13]; never-smokers [3]; continuing smokers, by age at stopping [14]
The numbers and sources
- Effect
- The share of the reducible excess risk remaining was 81.4% 1 year after quitting, 57.2% at 5 years, 36.9% at 10, 26.7% at 15 and 19.7% at 20 [11]. Lung cancer death had an RR of 0.64 (95% CI 0.55 to 0.76) in people who had quit for under 10 years, 0.33 for 10 to 20 years and 0.16 for over 20 years, against 0.11 in never smokers [12]. Heavy former smokers had 39.1% lower lung cancer risk than continuing smokers within 5 years, yet a hazard ratio of 3.85 (95% CI 1.80 to 8.26) against never smokers after 25 years [13]. Women who stopped at 25 to 34 had a lung cancer death rate 1.84 times that of never-smokers [3]. For UK men who stopped at 60, 50, 40 or 30, the risk of dying of lung cancer by 75 was 10%, 6%, 3% and 2%, against 16% in continuing smokers [14].
- Population
- 49 prospective cohorts in 20 countries [11]. 969,560 people in 24 studies [12]. 8,907 Framingham participants with 284 lung cancers over a median 28.7 years [13]. 1.2 million UK women [3]. 982 lung cancer cases and 3,185 controls in 1990, with UK national rates [14].
- Sources
- [11], [12], [13], [3], [14]
- Caveats
- Observational. People who quit after symptoms begin can make early quitters look worse, which is reverse causation. In heavy smokers, 4 in 10 lung cancers occurred more than 15 years after quitting [13].
Quitting smoking, against nicotine replacement
Shown to help more people stop smoking for at least 6 months than nicotine replacement therapy, about 4 more quitters per 100, in high-certainty pooled trials.
Compared with nicotine replacement therapy [1]; conventional quit treatments, nicotine replacement or behavioral [2]; nicotine replacement therapy, across 14 reviews [3]; nicotine replacement therapy, in the largest single trial [4]
The numbers and sources
- Effect
- Nicotine e-cigarettes raised quit rates against nicotine replacement therapy (RR 1.61, 95% CI 1.23 to 2.12, 11 studies, high-certainty evidence), about 4 more quitters per 100 (95% CI 1 to 7) [1]. A second meta-analysis found more biochemically confirmed abstinence than with conventional quit treatments (RR 1.77, 95% CI 1.29 to 2.44) [2]. Across 14 reviews, every pooled estimate favored nicotine e-cigarettes, with ratios typically 1.17 to 1.67 against nicotine replacement [3]. In the largest single trial, 1-year abstinence was 18.0% with e-cigarettes and 9.9% with nicotine replacement (RR 1.83, 95% CI 1.30 to 2.58), both with weekly behavioral support [4].
- Population
- 4,114 adults who smoked in 11 randomized trials, from 80 trials with 29,861 participants in all [1]. 3,253 adults in 5 trials of at least 6 months [2]. 14 reviews [3]. 886 adults at UK stop-smoking services [4].
- Sources
- [1], [2], [3], [4]
- Caveats
- The trials tested regulated nicotine e-cigarettes. Illicit products or products with other substances such as THC may differ [1]. Heterogeneity was moderate (I² 55%) [1]. Most trials were in high-income countries [3].
Quitting smoking, against e-cigarettes without nicotine
Shown to help more people stop smoking than e-cigarettes without nicotine, about 2 more quitters per 100, in two meta-analyses of randomized trials.
Compared with e-cigarettes without nicotine [1][2]; non-nicotine e-cigarettes or placebo, across 14 reviews [3]
The numbers and sources
- Effect
- Nicotine e-cigarettes probably raised quit rates against e-cigarettes without nicotine (RR 1.34, 95% CI 1.05 to 1.69, 7 studies, moderate-certainty evidence), about 2 more quitters per 100 [1]. A second review found an RR of 1.56 (95% CI 1.13 to 2.15) [2]. Across 14 reviews, ratios against non-nicotine e-cigarettes typically ran 1.46 to 2.09 [3].
- Population
- 1,918 adults in 7 trials [1]. Adults in 5 trials of at least 6 months [2]. 14 reviews [3].
- Sources
- [1], [2], [3]
- Caveats
- Evidence was downgraded for imprecision [1]. The two meta-analyses draw on overlapping trials, so their agreement is not fully independent.
Lung function and COPD after quitting
Shown to slow the yearly loss of lung function to about half the rate of continued smoking, in a large trial of smokers with early airway obstruction.
Compared with people who continued to smoke [15][16]; usual care, in the randomized comparison [16]; never smokers, with current and former smokers each set against them [17]
The numbers and sources
- Effect
- People who quit gained an average 47 mL (2%) of FEV1 in the year after quitting. Their later decline was 31 mL a year against 62 mL in continuing smokers [15]. At 11 years, men who quit lost 30.2 mL a year and women 21.5 mL, against 66.1 mL and 54.2 mL in continuing smokers. FEV1 was under 60% of predicted in 38% of continuing smokers and 10% of sustained quitters. The intervention group as randomized lost less lung function than usual care [16]. In pooled studies, COPD risk against never smokers was 3.51 (95% CI 3.08 to 3.99) in current smokers and 2.35 (95% CI 2.11 to 2.63) in ex-smokers, and limited data showed it falling with longer quitting [17].
- Population
- 3,926 smokers, mean age 48.5, with mild to moderate airway obstruction in 10 centers [15]. 77.4% of surviving participants at 11 years [16]. 133 studies of COPD [17].
- Sources
- [15], [16], [17]
- Caveats
- The comparison of quitters with continuing smokers is not randomized, since people chose whether to quit [15][16]. The pooled COPD estimates were markedly heterogeneous [17].
Mood after quitting
Linked to small improvements in depression, anxiety and stress after quitting, in a Cochrane review of mostly cohort data rated very low to moderate in certainty.
Compared with people who continued to smoke [19]
The numbers and sources
- Effect
- Against continuing to smoke, quitting was linked to lower anxiety (SMD -0.28, 95% CI -0.43 to -0.13), depression (SMD -0.30, 95% CI -0.39 to -0.21), mixed anxiety and depression (SMD -0.31) and stress (SMD -0.19), and more positive affect (SMD 0.22). New mixed anxiety and depression was less common in quitters (OR 0.76, 95% CI 0.66 to 0.86). Results were similar in people with mental illness [19].
- Population
- 102 studies with over 169,500 adults who smoked, followed at least 6 weeks [19].
- Sources
- [19]
- Caveats
- All studies were judged at serious risk of bias from confounding that changes over time, and there was some sign of publication bias [19]. People whose mood improves may find it easier to quit, which is reverse causation.
Quitting smoking, against behavioral support or no support
Shown to help more people stop smoking than behavioral support alone or no support, in pooled trials rated low in certainty because of risk of bias.
Compared with behavioral support only or no support [1]
The numbers and sources
- Effect
- Quit rates were higher with nicotine e-cigarettes than with behavioral support only or no support (RR 1.75, 95% CI 1.39 to 2.20, 11 studies, low-certainty evidence) [1].
- Population
- 7,214 adults who smoked in 11 trials [1].
- Sources
- [1]
- Caveats
- People in these trials knew whether they were given a device, and the review rated the evidence low in certainty for that reason [1].
Exposure markers after switching from cigarettes
Shown to lower exhaled carbon monoxide and most measured markers of potential harm in people who switched fully from cigarettes to e-cigarettes in quit trials.
Compared with people who kept smoking cigarettes [5]; dual users of e-cigarettes and cigarettes [5]
The numbers and sources
- Effect
- Exhaled carbon monoxide was 9.57 ppm lower in people using only e-cigarettes than in people who kept smoking (95% CI -17.30 to -1.83, 3 studies). Against continued smoking, 12 of 13 markers of potential harm were significantly lower in e-cigarette users, with no difference in the 13th. Against dual users, 12 of 25 markers were lower in e-cigarette users and 5 were lower in dual users [5].
- Population
- 1,299 adults who smoked and were given e-cigarettes in 9 studies in Greece, Italy, Poland, the UK and the US [5].
- Sources
- [5]
- Caveats
- People chose whether to switch fully, so the groups were not randomized against each other. Only one study had data on people who used neither product [5]. Lower exposure markers do not show lower disease.
Type 2 diabetes after quitting
Mixed results: in pooled cohorts, diabetes risk was higher in the first 5 years after quitting than in current or never smokers, then fell with time.
Compared with never smokers [18]
The numbers and sources
- Effect
- Against never smokers, the RR of type 2 diabetes was 1.54 (95% CI 1.36 to 1.74) in people who had quit under 5 years before, 1.18 at 5 to 9 years and 1.11 (95% CI 1.02 to 1.20) at 10 years or more. Current smokers had an RR of 1.37 (95% CI 1.33 to 1.42) [18].
- Population
- 88 prospective studies with 5,898,795 participants and 295,446 cases. 10 studies with 1,086,608 participants for time since quitting [18].
- Sources
- [18]
- Caveats
- Observational. Weight gain after quitting may explain the early rise. The review gives no direct comparison of recent quitters with people who kept smoking.