Socioeconomic status and smoking : exploring the behavioural determinants of health inequalities

It is well documented that there is a substantial social gradient in smoking behaviour. Smoking is more prevalent among lower socioeconomic groups and, furthermore, among smokers, those with lower socioeconomic status (SES) smoke more heavily and suffer worse health implications as a result. In addition, the knowledge of, access to, and use of healthcare resources vary widely across population subgroups. The concentration of smoking among low SES groups is based on complex individual and social processes and are fundamental to understanding the persistent unequal distribution of smoking. However, to date, little is known about the processes through which socioeconomic status translates into smoking, and even less about the relationship between SES and e-cigarette use. A better understanding of the complex relationship between SES and both smoking and vaping is warranted to further reduce the burden of tobacco related health disparities. In this thesis a socioecological model of behaviour was applied to examine mechanisms on multiple levels that may help explain the link between individual-level socioeconomic status and smoking. Potential mediating variables were tested on two levels ‚Äö- (1) via the exposure to daily stress in the immediate environment in Chapter 3 and (2) via the exposure to physical environments differing in the permission of smoking in Chapter 4. As research on smoking in recent years has shifted towards ecigarettes as a harm reduction tool in smoking cessation, this thesis also investigated whether a social gradient in the use and discontinuation in e-cigarette use is present (Chapter 5). Three complementary studies were conducted to build an evidence base to meet these aims. Specifically, the study in Chapter 3 involved the examination of the mediating role of daily stress experience on the relationship between individual- level SES indicators and smoking. EMA methods were applied examine time-varying links between socioeconomic status, the experience of daily stress, and smoking behaviour in the real world. The findings of the Study in Chapter 3 suggest that the experience of daily stress might function as one possible factor linking social disadvantage and smoking. In addition, the association between socioeconomic disadvantage and the experience of daily stress differed according to the indicators of social disadvantage used in this study. This suggests that the mechanisms of how social disadvantage translates into daily stress experience differ, depending on which facet for social disadvantage is used. Similarly, the study in Chapter 4 also applied EMA methods in order to examine temporally variable contexts and their legal implications on smoking, and whether these contexts vary as a function of SES. The findings from this suggest that SES is associated with smoking at least partially via differential exposure to smoking friendly environments, with smokers from lower SES backgrounds accessing more places where smoking is allowed. Together the first two studies were aimed to provide evidence for multilevel and momentary influences on the social gradient in smoking. Finally, the study in Chapter 5 explored whether a similar social gradient in the use and discontinuation of e-cigarettes could be observed. It was the first study to explicitly explore the associations between motivation to stop e-cigarette use and socioeconomic characteristics and the associations between socioeconomic and smoking characteristics and e-cigarette discontinuation. The results showed initial evidence for a social patterning in the discontinuation of e-cigarettes with users from low SES groups showing less motivation and fewer attempts to discontinue the use of e-cigarettes compared to users from high SES groups. The discontinuation from ecigarettes is not a positive or negative behaviour per se, it rather depends on whether continued e-cigarette use has a protective effect against relapse to smoking. More importantly, the relationship between SES and e-cigarettes use and the subsequent implications on health inequalities are not well understood. For example, a social gradient in switching to e-cigarettes may result in unequally distributed health benefits with the potential to either reduce or increase health inequalities. Similarly, socioeconomic differences in the discontinuation of e-cigarettes after successful smoking cessation may have disproportionate net health benefits. This would also have the potential to both, reduce or increase existing health inequalities. Across the research in this thesis social patterning in smoking and e-cigarette use were demonstrated, highlighting the need for further research into the underlying processes involved in smoking related health disparities. Specifically, the first two studies in this thesis expand our knowledge on the social gradient in smoking by providing initial empirical evidence for the validity of the proposed socioecological model on smoking behaviour. Additionally, the investigation of the use and discontinuation of e-cigarettes of the study in Chapter 5 further contributes to a better understanding of the determinants of health inequalities. Overall, the proposed studies serve to identify potentially modifiable factors for SES specific subgroups of the population who need most attention in policies aiming to reduce the burden of smoking and minimizing persistent health inequalities.