Smoking is the leading cause of disease and death worldwide. Most smokers want to quit, but stopping smoking can be very challenging. Quitting smoking can greatly improve people's health. Rewards, such as money or vouchers, can be used to encourage smokers to quit, and to reward them if they stay stopped. Such schemes can be run in workplaces, in clinics, and sometimes as community programmes.
We conducted our most recent search for studies in July 2018.
General trials: We found 33 trials, covering more than 21,600 people, that tested different rewards schemes to help smokers to quit. Two studies included smokers from mental health clinics, two from primary care clinics, two from head-and-neck cancer treatment clinics, two from colleges or universities, and one in Thai villages. Twenty-four of the trials were run in the USA. All the trials followed up participants for at least six months. Those who had quit were checked by testing their breath or bodily fluids. Rewards were cash payments, vouchers, or the return of money deposited by those taking part.
Pregnancy trials: We looked at studies in pregnant women separately. We found ten trials, nine based in the USA and one in the UK, covering 2571 pregnant women who smoked. Rewards were vouchers that were sometimes increased in value, depending on how long the woman had managed to stay quit.
General trials: Six months or more after the beginning of the trial, people receiving rewards were more likely to have stopped smoking than those in the control groups. Success rates continued beyond when the incentives had ended. Studies varied in the total amounts of rewards that were paid. There was no noticeable difference between trials paying smaller amounts (less than USD 100 (US dollars)) compared to those paying larger amounts (more than USD 700).
Pregnancy trials: Combining data from nine trials showed that women in the rewards groups were more likely to stop smoking than those in the control groups, both at the end of the pregnancy and after the birth of the baby.
Quality of the studies
Some of the studies did not provide enough data for us to fully assess their quality. Taking out the lowest-quality trials from the analysis did not change the results. Our certainty in our main findings is high. Our certainty in our findings in pregnant women is moderate, as some studies were of lower quality.
Overall there is high-certainty evidence that incentives improve smoking cessation rates at long-term follow-up in mixed population studies. The effectiveness of incentives appears to be sustained even when the last follow-up occurs after the withdrawal of incentives. There is also moderate-certainty evidence, limited by some concerns about risks of bias, that incentive schemes conducted among pregnant smokers improve smoking cessation rates, both at the end of pregnancy and post-partum. Current and future research might explore more precisely differences between trials offering low or high cash incentives and self-incentives (deposits), within a variety of smoking populations.
Financial incentives, monetary or vouchers, are widely used in an attempt to precipitate, reinforce and sustain behaviour change, including smoking cessation. They have been used in workplaces, in clinics and hospitals, and within community programmes.
To determine the long-term effect of incentives and contingency management programmes for smoking cessation.
For this update, we searched the Cochrane Tobacco Addiction Group Specialised Register, clinicaltrials.gov, and the International Clinical Trials Registry Platform (ICTRP). The most recent searches were conducted in July 2018.
We considered only randomised controlled trials, allocating individuals, workplaces, groups within workplaces, or communities to smoking cessation incentive schemes or control conditions. We included studies in a mixed-population setting (e.g. community, work-, clinic- or institution-based), and also studies in pregnant smokers.
We used standard Cochrane methods. The primary outcome measure in the mixed-population studies was abstinence from smoking at longest follow-up (at least six months from the start of the intervention). In the trials of pregnant women we used abstinence measured at the longest follow-up, and at least to the end of the pregnancy. Where available, we pooled outcome data using a Mantel-Haenzel random-effects model, with results reported as risk ratios (RRs) and 95% confidence intervals (CIs), using adjusted estimates for cluster-randomised trials. We analysed studies carried out in mixed populations separately from those carried out in pregnant populations.
Thirty-three mixed-population studies met our inclusion criteria, covering more than 21,600 participants; 16 of these are new to this version of the review. Studies were set in varying locations, including community settings, clinics or health centres, workplaces, and outpatient drug clinics. We judged eight studies to be at low risk of bias, and 10 to be at high risk of bias, with the rest at unclear risk. Twenty-four of the trials were run in the USA, two in Thailand and one in the Phillipines. The rest were European. Incentives offered included cash payments or vouchers for goods and groceries, offered directly or collected and redeemable online. The pooled RR for quitting with incentives at longest follow-up (six months or more) compared with controls was 1.49 (95% CI 1.28 to 1.73; 31 RCTs, adjusted N = 20,097; I2 = 33%). Results were not sensitive to the exclusion of six studies where an incentive for cessation was offered at long-term follow up (result excluding those studies: RR 1.40, 95% CI 1.16 to 1.69; 25 RCTs; adjusted N = 17,058; I2 = 36%), suggesting the impact of incentives continues for at least some time after incentives cease.
Although not always clearly reported, the total financial amount of incentives varied considerably between trials, from zero (self-deposits), to a range of between USD 45 and USD 1185. There was no clear direction of effect between trials offering low or high total value of incentives, nor those encouraging redeemable self-deposits.
We included 10 studies of 2571 pregnant women. We judged two studies to be at low risk of bias, one at high risk of bias, and seven at unclear risk. When pooled, the nine trials with usable data (eight conducted in the USA and one in the UK), delivered an RR at longest follow-up (up to 24 weeks post-partum) of 2.38 (95% CI 1.54 to 3.69; N = 2273; I2 = 41%), in favour of incentives.