Background
It is well documented that there is a substantial social gradient in smoking behavior: among smokers, those who are more socially disadvantaged also smoke more heavily [
1‐
3] and suffer worse health implications as a result [
4,
5]. In addition, the knowledge of, access to, and use of healthcare resources vary widely across population subgroups [
6]. The concentration of smoking among socially disadvantaged groups is based on complex individual and social processes and are fundamental to understanding the persistent unequal distribution of smoking [
7]. However, to date, little is known about the processes through which social disadvantage translates into smoking behavior.
Harwood and colleagues [
8] posited that psychosocial factors, such as perceived stress mediate the relationship between socioeconomic status (SES) and smoking. The unequal distribution of socioeconomic resources and the resulting socioeconomic disadvantages imply greater stress experience for those with less access to resources [
9,
10]. In addition, people who experience socioeconomic disadvantage also experience more stressful events and have fewer resources to successfully cope with this stress [
10‐
13]. This, in turn, might lead to increased smoking as a maladaptive way of coping with the stress [
14]; essentially, that some people may engage in smoking as a means of coping with stress [
15,
16].
Providing enhanced cessation support to smokers experiencing stress [
17,
18] could therefore help to reduce smoking prevalence, particularly among socially disadvantaged smokers [
10]. This idea implies a mediational relationship: Smoking is linked indirectly (mediation) to socioeconomic disadvantage through the experience of everyday stress, i.e., people would be assumed to smoke more as a response to experiencing higher levels of stress in their everyday lives through socioeconomic disadvantage. While this assumption is both plausible and supported by research on either ends (disadvantage leads to higher levels of daily stress [
19]; and higher levels of daily stress are associated with higher levels of smoking [
20], relatively few studies have investigated the role of daily stress in the social gradient in smoking.
Most previous studies examining the role of stress on the social gradient in smoking have operationalized stress as major live events or chronic stress [
12,
21]. For example, Mulder and colleagues reported that multiple chronic stressors (e.g., financial problems, low perceived life control and lack social support) were found to be directly related to smoking and partially mediated the relationship between educational level and smoking behavior [
10]. In essence: Socially disadvantaged individuals experience more stressful situations which is associated with higher smoking rates, compared to less disadvantaged individuals [
10,
13].
This view, however, is based on the idea that there are differences between individuals in how much chronic or acute stress they experience, and that these differences translate into stable differences in smoking rates between individuals (between-subject levels of analysis [
22,
23];). Such analyses cannot explore whether smokers smoke more cigarettes in situations or on days when they are more stressed (within-subject level of analysis [
24];). Where studies using between-subject level of analysis aim to compare groups of people, ascertaining whether situations in which individuals are stressed cues smoking calls for within-subject level of analysis. A previous study examining the link between the experience of daily stress and smoking for example showed that individuals reported smoking significantly more in situations when they experienced more stress [
20]. In addition, daily stress captures day-to-day experiences that potentially offer insight into the circumstances that may facilitate or preserve social inequalities in health [
19] and therefore might capture some of the variance in the association between aspects of social disadvantage and smoking. Grzywacz et al. [
19], for example, found that exposure to daily stress was status related: severity of stressful situations for lower SES individuals was higher than for individuals with higher SES. However, the potential of daily stress experience as a factor linking socioeconomic disadvantage and smoking has not been formally tested yet.
Examining the role of daily stress on the social gradient in smoking has both theoretical implications and may guide and inform the design of interventions targeted in particular at smokers with low socioeconomic status through reducing individual stress experience. The goals of these secondary analyses are to investigate whether social disadvantage, assessed through the unequal distribution of socioeconomic indicators, induces different levels of daily stress smokers experience and whether this is associated with smoking. It is hypothesized that perceived daily stress indirectly links indicators of social disadvantage and smoking in a way that more socially disadvantaged smokers perceive more daily stress, and that greater stress perception is in turn associated with more cigarettes smoked.
Results
Information on participant characteristics in regards to educational attainment, income and race are shown in Table
1. Lower educated participants were significantly older compared to higher educated participants but did not differ in regards to gender or baseline CPD. Participants who reported higher income did not differ in regards to demographic characteristics when compared with participants with lower income. African American smokers were significantly older and reported smoking fewer cigarettes at baseline compared to smokers with different ethnic background.
Table 1
Participant Characteristics
Age | 41.2 (11.2) | 42.6 (10.6)** | 40.0 (11.5) | 40.9 (11.2) | 41.5 (11.2) | 43.6* (9.8) | 39.7 (11.7) |
Gender (Male) | 55.2% (n = 107) | 56.8% (n = 46) | 54.0% (n = 61) | 54.9% (n = 50) | 55.3 (n = 57) | 46.6% (n = 34) | 60.3% (n = 73) |
CPD | 16.1 (6.5)*** | 16.5 (6.4) | 15.7 (6.6) | 15.9 (7.0) | 16.2 (6.0) | 14.2** (6.0) | 17.2 (6.6) |
The results for the multilevel mediation analysis are shown in Table
2. Participants with lower educational attainment perceived significantly more daily stress than participants with higher education. On days during which participants perceived more daily stress a higher number of cigarettes were smoked. This resulted in a small significant indirect effect of education via perceived daily stress on CPD while controlling for the direct effect of education on CPD, baseline CPD and gender. The findings show that perceived daily stress partially mediates the effect of education on CPD.
Table 2
Coefficient Estimates for parameters in 2–1-1 mediation model predicting CPD with education, income and race as indicators for social disadvantage
Fixed Effects (Measurement occasion level) |
Intercept CPD | 1.99 (1.13) | 2.20 (1.10)* | 1.74 (1.13) |
Intercept Daily Stress (DS) | 71.52 (2.56)*** | 76.00 (1.41)*** | 78.98 (1.45)*** |
Social Disadvantage (D) → DS | 8.42 (2.81)** | 6.95 (2.10)*** | −0.82 (2.18) |
DS → CPD | 0.01 (0.01)** | 0.01 (0.01)** | 0.01 (0.01)** |
Direct Effect SD → CPD | −0.53 (0.66) | −1.39 (0.55)* | −0.35 (0.61) |
Indirect Effect | 0.12 (0.04)* | 0.10 (0.05)* | −0.01 (0.03) |
Total Effect | −0.42 (0.65) | −1.29 (0.54)* | −0.37 (0.61) |
Random Effects (Participant level) |
Residual Variance Intercept DS | 203.07 (19.18)*** | 202.08 (18.92)*** | 212.89 (19.21)*** |
Residual Variance Intercept CPD | 16.16 (1.97)*** | 15.79 (1.91)*** | 16.17 (1.96)*** |
Covariance CPD DS | 12.61 (0.81)*** | 12.61 (0.81)*** | 12.61 (0.81)*** |
When using race as indicator for social disadvantage, the results show that AA smokers reported smoking fewer cigarettes than non-African American smokers
. However, AA smokers perceived significantly greater daily stress averaged across days of the monitoring period compared to non-AA individuals. Higher levels of average perceived stress within individuals in turn was related to greater increases in CPD when controlling for baseline CPD. This resulted in a significant indirect effect of racial background via perceived daily stress on CPD while controlling for the between-person direct effect of racial background on CPD. This indirect effect is the result of higher intercepts of daily stress and less CPD for AA smokers compared to non-AA smokers (Table
3). When separating the sample by race, the results show a non-significant negative effect of daily stress on CPD among AA smokers and a non-significant positive effect of daily stress on CPD among non-AA smokers. No indirect or direct effects were found for income as indicator of social disadvantage.
Table 3
Estimates for daily stress and CPD for AA and non-AA smokers
Intercept CPD (SD) | 9.952 (1.630) | 10.263 (1.213) |
Intercept Daily Stress (SD) | 82.542 (1.633) | 76.00 (1.41) |
Daily stress → CPD B (SD) | −0.013 (0.018) | 0.012 (0.015) |
Discussion
Using a within-subjects design, the aim of this project was to examine the role of the experience of daily stress as an intermediary process linking social disadvantage to cigarette consumption in an US sample of smokers. The results suggest that those individuals who are socially disadvantaged in terms of education and racial background experienced more daily stress. Those who experienced more daily stress in turn smoked more cigarettes, resulting in significant indirect effects of education and racial background on smoking, mediated by stress. Although the within-person positive indirect effect indicates that AA smokers are more affected by daily stress experience, the direct effect showed that AA participants smoked less overall compared to smokers from other racial backgrounds. This is in line with previous research suggesting that differences in CPD for AA and non-AA smokers may be explained through biological markers as AA smokers have a slower rate of nicotine metabolism [
37] and that smokers who have a faster rate of nicotine metabolism smoke more cigarettes per day [
38].
The findings suggest that the experience of daily stress might function as one possible factor linking social disadvantage and smoking [
14,
21]. Further, the results support previous findings that social disadvantage is associated with perceived stress [
39]. In addition, it could be shown that the association between social 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 indicator for social disadvantage is used. Each indicator of social disadvantage highlights important differences in terms of scope and implications on smoking, and although they overlap in how they affect smoking behavior, they should not be used interchangeably. We can only speculate, but for example, individuals with lower educational attainment may be more vulnerable to daily stress because their stressors are more severe and are experienced as more disruptive to their daily lives through a lack of material and psychological coping skills [
40]. Individuals with lower income may experience rather long-term stress in the form of financial strain, which may not necessarily translate into daily stress experience, but rather chronic stress.
Some limitations need to be noted when interpreting the findings. Firstly, we used a crude single-item measure of daily stress experience which may not adequately reflect how much stress participants experienced on a day-to-day basis. However, other studies have found that single-item stress measures are both reliable and valid, perform comparably to longer stress scales [
41] and have been successfully tested in real-world studies [
42]. Future research on the association between daily stress and smoking may consider collecting data on stress experience not just at the end of each day, but at multiple time points per day in order to get a more accurate measure of the intensity of daily stress. Assessing the different types of stressors linked to the stress experience may also yield deeper inside into the effects of stress on smoking. In addition, for social disadvantage, we used proxy measures such as education, income and racial background. Other indicators such as occupation, that tap explicitly into a person’s standing within a society may yield further inside into the effects of social disadvantage and smoking. Nevertheless, the indicators used in this study have been widely used in health research [
43]. Future studies might consider more comprehensive measures of social disadvantage in order to better capture differences in stress and smoking related to socioeconomic status. In order to gain sufficient and comparable sample sizes we dichotomized the indicators which may have minimized their effects on daily stress experience and smoking. Larger samples would yield the opportunity to explore effects of social disadvantage on daily stress experience and smoking more decidedly. For an EMA study however, the sample size was relatively large considering the vast amount of data collected for each individual participant.
Additionally, we have explored the effects of social disadvantage and daily stress experience on CPD, as the most important driver of nicotine intake. Other factors, such as puffing topography, or nicotine extraction per cigarette might also be important indicators of smoking as a means to relieving stress. In the context of an EMA study however, these factors would be difficult to measure and potentially add substantial participant burden. However, further research may explore ways to passively detect smoking instances, including puffing topography and how they relate to social disadvantage and daily stress experience.
Further, EMA data is correlational in nature which make causal interpretations difficult. Thus, reverse causation explanations (i.e. smoking causing stress) are also plausible. Some models such as the stress induction model posits that smoking induces stress [
44]. It has also been suggested that smoking may induce (financial) stress and that stress may lead to smoking induced deprivation [
45]. However, the findings of Study 1 are supported by experimental studies, showing that the experience of stress reduces the ability to resist smoking and increases both smoking intensity and reward [
46,
47]. Further, self-reports and situational characteristics have the potential to induce reactivity, which means that the monitoring itself might change participant’s behavior. To date, research on the potential that EMA methods might have on reactivity are mixed [
48,
49]. Nevertheless, EMA methods represent a substantial improvement over more common retrospective methods, as they maximize ecological validity, while avoiding recall bias [
50].
It must also be noted that the significant effects we found were only small (see Table
2). Hence, perceived stress does not offer a comprehensive explanation of how educational attainment and racial background might translate into smoking behavior. Other variables, such as the environment, social norms and networks may represent other processes linking SES and smoking [
51]. However, as we conducted secondary analysis for this study, socioeconomic variables were not the main focus when data was originally collected.
Lastly, the data collection ended about 9 years ago. A substantial amount of time has passed, in which smoking related public health interventions, changes in the costs of living etc. may have had significant effects on the relationship between social disadvantage and smoking. With rising inequalities however, we would expect the effects of social disadvantage on daily stress experience and smoking to be even stronger today. Replication of this study with more recent data is needed to confirm the results from our study.
In summary, the findings highlight the need for more focused research, with more diverse samples and better developed theory, in order to better understand the role of daily stress on social inequalities in smoking behavior. From an intervention perspective, examining the link between stress and smoking is important as smoking is suggested to be a maladaptive coping response to stress [
16]. Some social support interventions target stress management and coping skills [
52,
53]. As noted, the limited number of studies conducted to date broadly supports the premise that social support interventions targeting better management of daily stress may improve cessation outcomes, especially when focusing on socially disadvantaged smokers. The findings from this work, however, suggest that the direct effect of stress on day-to-day smoking is likely minimal, suggesting that additional work is required to understand how such interventions should be utilized.
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