Abstract: We include 57 studies (61 comparisons) in this updated review. We found 31 studies of workplace interventions aimed at individual workers, covering group therapy, individual counselling, self-help materials, nicotine replacement therapy, and social support, and 30 studies testing interventions applied to the workplace as a whole, i.e. environmental cues, incentives, and comprehensive programmes. The trials were generally of moderate to high quality, with results that were consistent with those found in other settings. Group therapy programmes (odds ratio (OR) for cessation 1.71, 95% confidence interval (CI) 1.05 to 2.80; eight trials, 1309 participants), individual counselling (OR 1.96, 95% CI 1.51 to 2.54; eight trials, 3516 participants), pharmacotherapies (OR 1.98, 95% CI 1.26 to 3.11; five trials, 1092 participants), and multiple intervention programmes aimed mainly or solely at smoking cessation (OR 1.55, 95% CI 1.13 to 2.13; six trials, 5018 participants) all increased cessation rates in comparison to no treatment or minimal intervention controls. Self-help materials were less effective (OR 1.16, 95% CI 0.74 to 1.82; six trials, 1906 participants), and two relapse prevention programmes (484 participants) did not help to sustain long-term abstinence. Incentives did not appear to improve the odds of quitting, apart from one study which found a sustained positive benefit. There was a lack of evidence that comprehensive programmes targeting multiple risk factors reduced the prevalence of smoking. 1. We found strong evidence that some interventions directed towards individual smokers increase the likelihood of quitting smoking. These include individual and group counselling, pharmacological treatment to overcome nicotine addiction, and multiple interventions targeting smoking cessation as the primary or only outcome. All these interventions show similar effects whether offered in the workplace or elsewhere. Self-help interventions and social support are less effective. Although people taking up these interventions are more likely to stop, the absolute numbers who quit are low. 2. We failed to detect an effect of comprehensive programmes targeting multiple risk factors in reducing the prevalence of smoking, although this finding was not based on meta-analysed data.  3. There was limited evidence that participation in programmes can be increased by competitions and incentives organized by the employer, although one trial demonstrated a sustained effect of financial rewards for attending a smoking cessation course and for long-term quitting. Further research is needed to establish which components of this trial contributed to the improvement in success rates. 4. Further research would be valuable in low-income and developing countries, where high rates of smoking prevail and smoke-free legislation is not widely accepted or enforced.

Plain-language summary: For this updated review (first published in 2003), we searched for randomized and quasi-randomized controlled trials, comparing the success rates of those in a work-based stop-smoking programme with those not involved in a work-based stop-smoking programme. The comparison could be between people within a single worksite, or between one or more worksites randomized to a stop-smoking programme or to no programme (cluster-randomized). The study had to include adults (over 18), and could be in any language and reported in any format, published or not. It had to report the numbers stopping smoking for at least six months. We searched for studies in July 2013, and identified ten new trials that fitted our criteria, making a total for this update of 61 comparisons across 57 included studies. We grouped them into two broad categories: those aimed at helping individual smokers, and those that targeted the workplace environment as a whole. The first group includes such methods as individual or group counselling, self help, nicotine replacement therapy (NRT) and other medications, help from workmates or other staff, and helping quitters to stay smoke-free. The second group includes environmental cues (posters, reminders), financial or material incentives, and comprehensive smoking cessation or health promotion programmes. The review found that programmes based on group behaviour therapy (eight trials; 1309 participants), on individual counselling (eight trials; 3516 participants), on medications (five trials; 1092 participants), and on several interventions combined (six trials; 5018 participants) helped people to stop smoking. The chances of stopping smoking using these methods are about the same in the workplace as they are in other settings. This review found that the following do not help people to stop smoking when delivered in the workplace: self-help methods, support from friends, family and workmates, relapse prevention programmes, environmental cues, or comprehensive programmes aimed at changing several high-risk behaviours. Results were mixed for incentives, with one high-quality trial finding a clear benefit for incentives while the remaining five did not. Earlier studies tended to be less well-conducted and reported than recent ones. Fewer than one in five studies randomized their study population by an acceptable method. Two-thirds of the studies checked the accuracy of those who said they had quit by testing their breath, blood or urine. The results were generally in line with findings from other reviews of those ways of quitting in any setting. The 'Summary of findings' table shows that the trials were generally rated as being of moderate to high quality, further confirming the strength of our findings. Future research might examine what features of the large incentives trial made it more successful than other trials in that group. It would also be helpful to have more trials from developing and low-income countries, where smoking rates remain high and anti-smoking laws are not widely enforced.