Background A persistent socioeconomic gradient in smoking has been observed in a variety of populations. While stress is hypothesised to play a mediating role, the extent of this mediation is unclear. We used marginal structural models (MSMs) to estimate the proportion of the effect of socioeconomic status (SES) on smoking, which can be explained by an indicator of stress related to SES, experiences of chronic financial stress.
Methods Using the Health and Retirement Study (waves 7–12, 2004–2014), a survey of older adults in the USA, we analysed a total sample of 15 260 people. A latent variable corresponding to adult SES was created using several indicators of socioeconomic position (wealth, income, education, occupation and labour force status). The main analysis was adjusted for other factors that influence the pathway from adult SES to stress and smoking, including personal coping resources, health-related factors, early-life SES indicators and other demographic variables to estimate the proportion of the effect explained by these pathways.
Results Compared with those in the top SES quartile, those in the bottom quartile were more than four times as likely to be current smokers (rate ratio 4.37, 95% CI 3.35 to 5.68). The estimate for the MSM attenuated the effect size to 3.34 (95% CI 2.47 to 4.52). Chronic financial stress explained 30.4% of the association between adult SES and current smoking (95% CI 13 to 48).
Conclusion While chronic financial stress accounts for part of the socioeconomic gradient in smoking, much remains unexplained.
- social class
- social inequalities
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Contributors AP conceived and planned the study in discussion with AS. AP conducted the data analysis. AP and AS discussed the analysis and interpreted the findings. AP drafted the manuscript. AS edited the manuscript. AS supervised the project.
Funding This research was supported by Canada Research Chair in Population Health Equity awarded to Dr Siddiqi by the Canadian Institutes of Health Research.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Our study drew on secondary, publicly available data and was thus exempt from ethics approval, as stipulated in Article 2.2 of the Tri-Council Policy Statement: Ethical Conduct of Research Involving Humans - TCPS 2 (2018).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available in a public, open access repository. The data used in this study are available through the Health and Retirement Study website (https://hrs.isr.umich.edu/).
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