Do interventions to help adults stop smoking cigarettes work differently depending on people’s socioeconomic background?

Key messages

• We have little or no confidence in the evidence for all treatments. This means there is no clear evidence to support using different stop-smoking interventions for people from lower versus higher socioeconomic groups, or that any one intervention would have an effect on health inequalities. However, this conclusion may change as more research becomes available.

• More studies that report quit rates by socioeconomic status for each study group are needed.

Quitting smoking and differences in socioeconomic status

Smoking is the leading risk factor for disease and premature death, killing one in two users and eight million people worldwide every year. People who smoke are at increased risk of heart disease, lung disease, and cancer.

Many different types of treatments can help people quit smoking. These treatments include medication or behavioural support, such as counselling, and can be delivered in diverse ways.

People from lower socioeconomic groups (e.g. people living on lower incomes, who are unemployed, or who have lower levels of education) are more likely to smoke but less likely to quit with the help of current treatments compared to people from higher socioeconomic groups.

Potential impact of quitting smoking on health inequalities

Health inequalities are differences in health between groups of people. As smoking is uniquely harmful and deadly, higher numbers of people smoking leads to unequal smoking-related disease and death in disadvantaged groups. This makes smoking a leading driver of health inequalities. Quitting smoking is vital to reduce this risk and also to reduce differences in health between people from different socioeconomic groups.

What did we want to find out?

We wanted to know whether current treatments to help adults quit smoking tobacco cigarettes work better or worse in people from different socioeconomic groups, and their potential impact on health equalities.

What did we do?

We searched for studies that looked at any treatments an adult (aged 18 years or older) might use to help them stop smoking tobacco cigarettes. We looked for randomised controlled trials, where people were randomly assigned to different treatment groups.

We compared and summarised study results on the number of people who quit smoking after at least six months, in lower compared to higher socioeconomic groups. We then categorised the potential impact of the intervention on health equality. We rated our confidence in the evidence based on factors such as study methods and sizes.

What did we find?

We found 77 studies reporting on 127,791 adults who smoke. They investigated a range of medications and behavioural support to help people stop smoking. Seventy-three studies were conducted in high-income countries.

What are the main results of our review?

Nicotine electronic cigarettes and cytisine (a medicine) each had a greater effect on quit rates in lower rather than higher socioeconomic groups. This suggests each of these interventions may have a possibly positive impact on health equality compared to the control intervention. We found that bupropion (an antidepressant) had a greater effect on quit rates in higher rather than lower socioeconomic groups, indicating a possibly negative impact on health equality. The evidence on nicotine replacement therapy was unclear, and no evidence was available for varenicline (a medicine). However, we are very uncertain about these results.

Evidence on print-based self-help materials, text-messaging, and financial incentives to stop smoking suggested lower quit rates in lower socioeconomic groups compared to higher groups. This suggests that these interventions have a possibly negative impact on health equality, compared to control. Evidence on face-to-face counselling suggested no difference between socioeconomic groups, while telephone counselling and internet-based interventions showed a greater effect on quit rates in lower compared to higher socioeconomic groups. Again, we have limited confidence in these results.

What are the limitations of the evidence?

We have little to no confidence in the findings due to: (1) the small numbers of studies; (2) variations in intervention impact on health equality between studies; (3) issues with the design or conduct of studies; and (4) limited data on the number of people who quit smoking by socioeconomic status by study group, which prevented further analyses. More evidence may change or strengthen our findings.

How current is this evidence?

The evidence is current to 1 May 2023.

Authors' conclusions: 

Currently, there is no clear evidence to support the use of differential individual-level smoking cessation interventions for people from lower or higher SES groups, or that any one intervention would have an effect on health inequalities. This conclusion may change as further data become available.

Many studies did not report sufficient data to be included in a meta-analysis, despite having tested the association of interest. Further RCTs should collect, analyse, and report quit rates by measures of SES, to inform intervention development and ensure recommended interventions do not exacerbate but help reduce health inequalities caused by smoking.

Read the full abstract...
Background: 

People from lower socioeconomic groups are more likely to smoke and less likely to succeed in achieving abstinence, making tobacco smoking a leading driver of health inequalities. Contextual factors affecting subpopulations may moderate the efficacy of individual-level smoking cessation interventions. It is not known whether any intervention performs differently across socioeconomically-diverse populations and contexts.

Objectives: 

To assess whether the effects of individual-level smoking cessation interventions on combustible tobacco cigarette use differ by socioeconomic groups, and their potential impact on health equalities.

Search strategy: 

We searched the Cochrane Database of Systematic Reviews from inception to 1 May 2023 for Cochrane reviews investigating individual-level smoking cessation interventions. We selected studies included in these reviews that met our criteria. We contacted study authors to identify further eligible studies.

Selection criteria: 

We included parallel, cluster or factorial randomised controlled trials (RCTs) investigating any individual-level smoking cessation intervention which encouraged complete cessation of combustible tobacco cigarette use compared to no intervention, placebo, or another intervention in adults. Studies must have assessed or reported smoking quit rates, split by any measure of socioeconomic status (SES) at longest follow-up (≥ six months), and been published in 2000 or later.

Data collection and analysis: 

We followed standard Cochrane methods for screening, data extraction, and risk of bias assessment. We assessed the availability of smoking abstinence data by SES in lieu of selective reporting.

The primary outcome was smoking cessation quit rates, split by lower and higher SES, at the longest follow-up (≥ six months). Where possible, we calculated ratios of odds ratios (ROR) with 95% confidence intervals (CIs) for each study, comparing lower to higher SES. We pooled RORs by intervention type in random-effects meta-analyses, using the generic inverse-variance method. We subgrouped by type of SES indicator and economic classification of the study country. We summarised all evidence in effect direction plots and categorised the intervention impact on health equality as: positive (evidence that the relative effect of the intervention on quit rates was greater in lower rather than higher SES groups), possibly positive, neutral, possibly neutral, possibly negative, negative, no reported statistically significant difference, or unclear. We evaluated certainty using GRADE.

Main results: 

We included 77 studies (73 from high-income countries), representing 127,791 participants. We deemed 12 studies at low overall risk of bias, 13 at unclear risk, and the remaining 52 at high risk. Included studies investigated a range of pharmacological interventions, behavioural support, or combinations of these.

Pharmacological interventions

We found very low-certainty evidence for all the main pharmacological interventions compared to control. Evidence on cytisine (ROR 1.13, 95% CI 0.73 to 1.74; 1 study, 2472 participants) and nicotine electronic cigarettes (ROR 4.57, 95% CI 0.88 to 23.72; 1 study, 989 participants) compared to control indicated a greater relative effect of these interventions on quit rates in lower compared to higher SES groups, suggesting a possibly positive impact on health equality. CIs for both estimates included the possibility of no clinically important difference and of favouring higher SES groups. There was a lower relative effect of bupropion versus placebo on quit rates in lower compared to higher SES groups, indicating a possibly negative impact on health equality (ROR 0.05, 95% CI 0.00 to 1.00; from 1 of 2 studies, 354 participants; 1 study reported no difference); however, the CI included the possibility of no clinically important difference. We could not determine the intervention impact of combination or single-form nicotine replacement therapy on relative quit rates by SES. No studies on varenicline versus control were included.

Behavioural interventions

We found low-certainty evidence of lower quit rates in lower compared to higher SES groups for print-based self-help (ROR 0.85, 95% CI 0.52 to 1.38; 3 studies, 4440 participants) and text-messaging (ROR 0.76, 95% CI 0.47 to 1.23; from 3 of 4 studies, 5339 participants; 1 study reported no difference) versus control, indicating a possibly negative impact on health equality. CIs for both estimates included the possibility of no clinically important difference and of favouring lower SES groups.

There was very low-certainty evidence of quit rates favouring higher SES groups for financial incentives compared to balanced intervention components. However, the CI included the possibility of no clinically important difference and of favouring lower SES groups (ROR 0.91, 95% CI 0.45 to 1.85; from 5 of 6 studies, 3018 participants; 1 study reported no difference). This indicates a possibly negative impact on health equality. There was very low-certainty evidence of no difference in quit rates by SES for face-to-face counselling compared to less intensive counselling, balanced components, or usual care. However, the CI included the possibility of favouring lower and higher SES groups (ROR 1.26, 95% CI 0.18 to 8.93; from 1 of 6 studies, 294 participants; 5 studies reported no difference), indicating a possibly neutral impact.

We found very low-certainty evidence of a greater relative effect of telephone counselling (ROR 4.31, 95% CI 1.28 to 14.51; from 1 of 7 studies, 903 participants; 5 studies reported no difference, 1 unclear) and internet interventions (ROR 1.49, 95% CI 0.99 to 2.25; from 1 of 5 studies, 4613 participants; 4 studies reported no difference) versus control on quit rates in lower versus higher SES groups, suggesting a possibly positive impact on health equality. The CI for the internet intervention estimate included the possibility of no difference. Although the CI for the telephone counselling estimate only favoured lower SES groups, most studies narratively reported no clear evidence of interaction effects.