Background
We reviewed the evidence about whether exercise helps people who want to quit smoking, or have recently stopped smoking, to stop smoking for at least six months. Taking regular exercise may help people give up smoking by helping with cigarette withdrawal and cravings, and by helping them to manage weight gain, which can be a concern among people trying to quit.
Study characteristics
We found 24 studies with a total of 7279 people. Two studies focused on helping those who had recently stopped smoking and the rest of the studies included current smokers who wished to quit. All the studies were conducted with adults. Eleven studies were with women only and one with men only. Most studies recruited fairly inactive people. Most studies offered supervised and group-based, aerobic-type exercise. The evidence is up-to-date to May 2019.
Key results
When we combined the results of 21 studies (6607 participants) which compared exercise and smoking-cessation programmes to smoking cessation programmes alone, there was no evidence that exercise increased quit rates at six months or longer. There was no evidence that the effect was different for different types of exercise. When we combined results from two studies (453 participants), there was no evidence that exercise helped people who had recently quit to stay quit.
Quality of evidence
We judged the quality of evidence for whether exercise programmes help people quit smoking as low certainty, suggesting that future research could change these results. The low certainty is because we cannot rule out chance as an explanation for the suggested slight benefit. It could be that exercise may not help at all, or it could be that supporting people to do exercise modestly increases quit rates. We do not know which of these is true. We also consider that a good number of the trials may be biased. We have concerns that small studies which found smaller effects were less likely to be published than small studies which found bigger effects, making the average result misleading. We judged the evidence from two studies examining whether exercise helps people to avoid relapse to smoking to be of very low certainty, again suggesting that more research is needed. This is due to imprecision of the estimated effects and a high risk of bias in the methods used by one of the studies.
There is no evidence that adding exercise to smoking cessation support improves abstinence compared with support alone, but the evidence is insufficient to assess whether there is a modest benefit. Estimates of treatment effect were of low or very low certainty, because of concerns about bias in the trials, imprecision and publication bias. Consequently, future trials may change these conclusions.
Taking regular exercise, whether cardiovascular-type exercise or resistance exercise, may help people to give up smoking, particularly by reducing cigarette withdrawal symptoms and cravings, and by helping to manage weight gain.
To determine the effectiveness of exercise-based interventions alone, or combined with a smoking cessation programme, for achieving long-term smoking cessation, compared with a smoking cessation intervention alone or other non-exercise intervention.
We searched the Cochrane Tobacco Addiction Group Specialised Register for studies, using the term 'exercise' or 'physical activity' in the title, abstract or keywords. The date of the most recent search was May 2019.
We included randomised controlled trials that compared an exercise programme alone, or an exercise programme as an adjunct to a cessation programme, with a cessation programme alone or another non-exercise control group. Trials were required to recruit smokers wishing to quit or recent quitters, to assess abstinence as an outcome and have follow-up of at least six months.
We followed standard Cochrane methods. Smoking cessation was measured after at least six months, using the most rigorous definition available, on an intention-to-treat basis. We calculated risk ratios (RRs) and 95% confidence intervals (CIs) for smoking cessation for each study, where possible. We grouped eligible studies according to the type of comparison, as either smoking cessation or relapse prevention. We carried out meta-analyses where appropriate, using Mantel-Haenszel random-effects models.
We identified 24 eligible trials with a total of 7279 adult participants randomised. Two studies focused on relapse prevention among smokers who had recently stopped smoking, and the remaining 22 studies were concerned with smoking cessation for smokers who wished to quit. Eleven studies were with women only and one with men only. Most studies recruited fairly inactive people. Most of the trials employed supervised, group-based cardiovascular-type exercise supplemented by a home-based exercise programme and combined with a multi-session cognitive behavioural smoking cessation programme. The comparator in most cases was a multi-session cognitive behavioural smoking cessation programme alone. Overall, we judged two studies to be at low risk of bias, 11 at high risk of bias, and 11 at unclear risk of bias.
Among the 21 studies analysed, we found low-certainty evidence, limited by potential publication bias and by imprecision, comparing the effect of exercise plus smoking cessation support with smoking cessation support alone on smoking cessation outcomes (RR 1.08, 95% CI 0.96 to 1.22; I2 = 0%; 6607 participants). We excluded one study from this analysis as smoking abstinence rates for the study groups were not reported. There was no evidence of subgroup differences according to the type of exercise promoted; the subgroups considered were: cardiovascular-type exercise alone (17 studies), resistance training alone (one study), combined cardiovascular-type and resistance exercise (one study) and type of exercise not specified (two studies). The results were not significantly altered when we excluded trials with high risk of bias, or those with special populations, or those where smoking cessation intervention support was not matched between the intervention and control arms. Among the two relapse prevention studies, we found very low-certainty evidence, limited by risk of bias and imprecision, that adding exercise to relapse prevention did not improve long-term abstinence compared with relapse prevention alone (RR 0.98, 95% CI 0.65 to 1.47; I2 = 0%; 453 participants).