Can incentives help smokers to quit in the medium to long term?

Background:

Incentives, usually as cash or as vouchers, are widely used to encourage smokers to try to quit, and to reward them if they succeed. Such schemes can be run in workplaces, in clinics, and sometimes as community programmes. For this third update of our review we now include studies in pregnant women. Another change is that we have separated out trials which use incentives from those which use competitions; we will now cover the competition trials in a separate update.

Study characteristics:

Mixed-population trials: We found 21 trials, covering more than 8400 people, which looked at different incentive schemes to help smokers to try and quit. Our most recent search was in December 2014, although we also include two trials published after this date. Ten of the studies were set in clinics or health centres, one in villages in Thailand served by community health workers, two in research centres, and the rest in worksites. All but six of the trials were run in the USA. All the trials followed up their participants for at least six months, and checked whether or not the quitters had succeeded by testing their breath or bodily fluids. The incentives included lottery tickets, prize draws, cash payments, vouchers for goods and groceries, and in six trials the return of money deposited by those taking part.

Pregnancy trials: We found nine trials, eight based in the USA and one in the UK, covering almost 1600 women trying to quit smoking while pregnant. Rewards were vouchers for goods or groceries, and were sometimes increased in value depending on how long the woman had managed to stay quit.

Key results:
Mixed-population trials: Six months or more after the beginning of the trial, people receiving incentives were more likely to have quit than those in the control groups. Only three trials reported prolonged success beyond the close of the programme. One USA trial, paying quitters up to USD 750, found that nearly three times as many people stopped smoking in the experimental group compared to the controls. Another USA trial paying out up to USD 800 per quitter found that nearly twice as many people receiving payments stopped smoking compared to the control group. This trial also compared paying out rewards to returning the participant's own money to them if they managed to quit. Although more people in this trial took part in the rewards programmes than in the deposit programmes, the proportion of quitters in each group favoured the deposit-refund programme. The third trial was based in Thailand and rewarded quitters by returning their own money to them with bonuses. Although medium-term quit rates were encouraging, the deposit-return programmes generally struggled to match the rewards programmes for numbers willing to take part.

Pregnancy trials: Eight of the nine trials with usable data showed that women in the incentive groups were more likely to quit than those in the control groups, both at the end of the pregnancy and at the longest follow-up (up to 24 weeks after the birth). Four of the trials confirmed that payments made to reward a successful quit attempt ('contingent' payments), compared to fixed payments for attending the antenatal appointment ('non-contingent'), produced higher quit rates. The largest trial, based in the UK, used the NHS stop-smoking service to deliver support in quitting, and achieved a quit rate in the incentives group almost four times as high as in the control group. One trial which weighted the payments to meet the challenge of greater withdrawal symptoms in the first two weeks of quitting found that this made little difference to the women's chances of success.

Quality of the evidence:
We rated the overall quality of the older mixed-population studies as low, but with later trials (2000 onwards) more likely to be well conducted and fully reported. Removing the early trials from the calculations made very little difference to the results at six-month follow-up, but did increase the advantage for incentives at 12 month-follow-up. The pregnancy trials were all published within the last 15 years, and were generally of moderate quality.

Authors' conclusions: 

Incentives appear to boost cessation rates while they are in place. The two trials recruiting from work sites that achieved sustained success rates beyond the reward schedule concentrated their resources into substantial cash payments for abstinence. Such an approach may only be feasible where independently-funded smoking cessation programmes are already available, and within a relatively affluent and educated population. Deposit-refund trials can suffer from relatively low rates of uptake, but those who do sign up and contribute their own money may achieve higher quit rates than reward-only participants. Incentive schemes conducted among pregnant smokers improved the cessation rates, both at the end-of-pregnancy and post-partum assessments. Current and future research might continue to explore the scale, loading and longevity of possible cash or voucher reward schedules, within a variety of smoking populations.

Read the full abstract...
Background: 

Material or financial incentives are widely used in an attempt to precipitate or reinforce behaviour change, including smoking cessation. They operate in workplaces, in clinics and hospitals, and to a lesser extent within community programmes. In this third update of our review we now include trials conducted in pregnant women, to reflect the increasing activity and resources now targeting this high-risk group of smokers.

Objectives: 

To determine whether incentives and contingency management programmes lead to higher long-term quit rates.

Search strategy: 

We searched the Cochrane Tobacco Addiction Group Specialised Register, with additional searches of MEDLINE, EMBASE, CINAHL and PsycINFO. The most recent searches were in December 2014, although we also include two trials published in 2015.

Selection criteria: 

We considered randomised controlled trials, allocating individuals, workplaces, groups within workplaces, or communities to experimental or control conditions. We also considered controlled studies with baseline and post-intervention measures. We include studies in a mixed-population setting (e.g. community-, work-, institution-based), and also, for this update, trials in pregnant smokers.

Data collection and analysis: 

One author (KC) extracted data and a second (JH-B) checked them. We contacted study authors for additional data where necessary. The main outcome measure in the mixed-population studies was abstinence from smoking at longest follow-up, and at least six months from the start of the intervention. In the trials of pregnant smokers abstinence was measured at the longest follow-up, and at least to the end of the pregnancy.

Main results: 

Twenty-one mixed-population studies met our inclusion criteria, covering more than 8400 participants. Ten studies were set in clinics or health centres, one in Thai villages served by community health workers, two in academic institutions, and the rest in worksites. All but six of the trials were run in the USA. The incentives included lottery tickets or prize draws, cash payments, vouchers for goods and groceries, and in six trials the recovery of money deposited by those taking part. The odds ratio (OR) for quitting with incentives at longest follow-up (six months or more) compared with controls was 1.42 (95% confidence interval (CI) 1.19 to 1.69; 17 trials, [20 comparisons], 7715 participants). Only three studies demonstrated significantly higher quit rates for the incentives group than for the control group at or beyond the six-month assessment: One five-arm USA trial compared rewards- and deposit-based interventions at individual and group level, with incentives available up to USD 800 per quitter, and demonstrated a quit rate in the rewards groups of 8.1% at 12 months, compared with 4.7% in the deposits groups. A direct comparison between the rewards-based and the deposit-based groups found a benefit for the rewards arms, with an OR at 12 months of 1.76 (95% CI 1.22 to 2.53; 2070 participants). Although more people in this trial accepted the rewards programmes than the deposit programmes, the proportion of quitters in each group favoured the deposit-refund programme. Another USA study rewarded both participation and quitting up to USD 750, and achieved sustained quit rates of 9.4% in the incentives group compared with 3.6% for the controls. A deposit-refund trial in Thailand also achieved significantly higher quit rates in the intervention group (44.2%) compared with the control group (18.8%), but uptake was relatively low, at 10.5%. In the remaining trials, there was no clear evidence that participants who committed their own money to the programme did better than those who did not, or that contingent rewards enhanced success rates over fixed payment schedules. We rated the overall quality of the older studies as low, but with later trials (post-2000) more likely to meet current standards of methodology and reporting.

Eight of nine trials with usable data in pregnant smokers (seven conducted in the USA and one in the UK) delivered an adjusted OR at longest follow-up (up to 24 weeks post-partum) of 3.60 (95% CI 2.39 to 5.43; 1295 participants, moderate-quality studies) in favour of incentives. Three of the trials demonstrated a clear benefit for contingent rewards; one delivered monthly vouchers to confirmed quitters and to their designated 'significant other supporter', achieving a quit rate in the intervention group of 21.4% at two months post-partum, compared with 5.9% among the controls. Another trial offered a scaled programme of rewards for the percentage of smoking reduction achieved over the course of the 12-week intervention, and achieved an intervention quit rate of 31% at six weeks post-partum, compared with no quitters in the control group. The largest (UK-based) trial provided intervention quitters with up to GBP 400-worth of vouchers, and achieved a quit rate of 15.4% at longest follow-up, compared to the control quit rate of 4%. Four trials confirmed that payments made to reward a successful quit attempt (i.e. contingent), compared to fixed payments for attending the antenatal appointment (non-contingent), resulted in higher quit rates. Front-loading of rewards to counteract early withdrawal symptoms made little difference to quit rates.