Background Tobacco smoking is a major cause of chronic disease and premature mortality. Its effects are socially patterned. Observational studies show that low socioeconomic status [SES] is associated with higher smoking prevalence and lower cessation rates. Interventions in primary care may improve or exacerbate health inequalities depending on socioeconomic patterning of access and uptake. Data on the impact of trials of smoking cessation interventions delivered in primary care on health inequalities by SES have not been synthesised. We examined the impact of smoking cessation interventions delivered in primary care on inequalities in health by socioeconomic status.

Methods We searched the Cochrane database of systematic reviews from inception until June 2019. We included reviews of trials of smoking cessation interventions delivered in primary care and published in English.

Results We identified eight Cochrane reviews (413 studies). Eighty five studies included an intervention delivered in primary care. Interventions were: behavioural, (very) brief advice, and pharmacological (including nicotine replacement therapy). Full texts were accessed for 70 studies; 17 reported an SES measure. Two studies targeted low-SES groups. There was heterogeneity in SES measures used across the studies, which included household income, occupational level and social class. Three studies analysed SES as a predictor of effectiveness of the smoking cessation intervention; none found that effectiveness differed by SES.

Discussion This summary and critique of Cochrane reviews demonstrates that trials of smoking cessation interventions delivered in primary care are not designed to allow analysis of effects by measures of SES. Studies rarely reported SES of participants at baseline and hardly ever as a predictor of smoking cessation. Our work highlights the need for routine reporting of SES amongst trials and greater consensus in included measures. Consistent reporting of a core set of SES indicators will enable testing of similarities between trial groups and differential effects by SES.