Population tobacco control interventions and their effects on social inequalities in smoking: placing an equity lens on existing systematic reviews

BACKGROUND: With smoking increasingly confined to lower socio-economic groups, the tobacco control community has been urged to identify which population-level tobacco control interventions work in order to help tackle smoking-related health inequalities. Systematic reviews have a crucial role to play in this task. This overview was therefore carried out in order to (i) summarise the evidence from existing systematic reviews of population-level tobacco control interventions, and (ii) assess the need for a new systematic review of primary studies, with the aim of assessing the differential effects of such interventions. METHODS: Systematic review methods were used to evaluate existing systematic reviews that assessed a population-level tobacco control intervention and which reported characteristics of included participants in terms of at least one socio-demographic or socio-economic factor. RESULTS: Nineteen systematic reviews were included. Four reviews assessed interventions aimed at the population level alone, whilst fifteen included at least one primary study that examined this type of intervention. Four reviews assessed youth access restrictions, one assessed the effects of increasing the unit price of tobacco, and six assessed smoking bans or restrictions. Of the eight remaining reviews, six assessed multi-component community based interventions, in which the population-level interventions were part of a wider tobacco control programme, and two assessed the impact of smoking bans or restrictions in reducing exposure to environmental tobacco smoke. We found tentative evidence that the effect of increasing the unit price of tobacco products may vary between ethnic and socio-economic groups, and between males and females. However, differences in the context and the results of different reviews made it difficult to draw any firm conclusions. Few identified reviews explicitly attempted to examine differences in intervention effects between socio-demographic groups. Therefore on the basis of these reviews the potential for smoking bans, and youth access restrictions to decrease social inequalities in smoking remains unknown. CONCLUSION: There is preliminary evidence that increases in the unit price of tobacco may have the potential to reduce smoking related health inequalities. There is a need for equity effects to be explicitly evaluated in future systematic reviews and in primary research assessing the effects of population tobacco control interventions.