The purpose of this study was to investigate mediators of educational disparities in adiposity in the Czech middle-aged population. The mediating pathways were assessed separately for men and women, which allowed for evaluating possible sex differences. Men presented worse quality of lifestyle but reported higher income and lower burden of mental health difficulties, as compared to women. In both sexes, education was associated with almost all potential mediators except for alcohol consumption and mental health in men; however, not all these mediators were significantly associated with adiposity; thus, the observed indirect effects considerably differed between sexes.
In women, increased adiposity in those with lower educational levels seems to be the consequence of a mixture of inappropriate diet and suffering from economic disadvantage. Among the identified mediators, dietary risk and income had the largest mediation ratio of 16% and 15%, respectively. On the contrary, in men, none of the assessed mediators could partially explain the reversed gradient between education and adiposity. Only pathway via sedentary behavior had a significant indirect effect but showed the association in the opposite direction than for the direct effect. In other words, sedentary behavior in men did not partially explain why men with lower education presented increased adiposity despite the considerable strength of the mediation ratio (24%). The opposite mediation effect of sedentary behavior was also observed in women, but with a lower magnitude (8%).
The opposite indirect effect found in sedentary behaviors suggests that in both sexes, the protective potential of higher education in adiposity risk is decreased by the influence of a sedentary lifestyle, which is more prevalent in higher educational groups. Based on the previous studies, increased sedentary behaviors are generally more prevalent in men [25] than women [25] and in higher socioeconomic positions, which may be explained by higher demands for sitting-based tasks in higher-status occupations [26]. Sedentary behavior is an important risk factor in modern society. An increasing trend in sedentary behaviors observed in the last 20 years in European countries [25] could extend the burden of increased adiposity into higher socioeconomic strata and thereby suppress the protective potential of higher education. Lifestyle interventions should therefore emphasize strategies for reducing sitting time in the population, with a special emphasis on higher socioeconomic groups.
It is noteworthy that mediators investigated in the current study explained only one-third of the total association between education and adiposity in women and one-fifth in men. It seems that there are other factors not included in our analysis whose mediating potential exceeds the investigated variables. Lower education may be reflected in reduced knowledge about health and limited health literacy [27], which is the individual ability to obtain, understand, evaluate, and apply health information [28]. One previous study, including 88,384 participants of Lifelines Cohort Study [29] assessed the mediation potential of health literacy in the educational disparities in metabolic syndrome. The study found that health literacy mediated 7.1% of the association in men and 5.9% in women. Besides the mediating role of health literacy, the study also found that self-management, defined as the individual ability to realize and sustain well-being, contributed to educational differences in metabolic syndrome in both sexes [29].
Moreover, although our study investigated a wide spectrum of health behavior factors, we did not consider all individual aspects. For example, our study investigated dietary risk as the frequency of consumption of specific food groups, which as a mediator explained 16% of the total effect in women but did not emerge as a significant mediator in men. This does not mean that an individual diet does not contribute to obesity development, but individual diet results from a variety of factors, including daily eating behavior, cooking habits, or portion size. One case-control study from France [30] including 318 obese and 371 non-obese participants, assessed the mediation potential of eating attitudes, circumstances, and behaviors in the association between socioeconomic status and obesity. Among 10 factors tested, the results showed a significant mediation effect of eating off a large plate, eating at night, and uncontrolled eating [30].
Educational disparities are not reflected only in individual habits and abilities but are also closely related to the disadvantaged life environment. The availability of healthy options is often higher in affluent neighborhoods compared to socially disadvantaged areas [31]. Besides that, the external environment influences adiposity both at the level of the social environment as well as the physical environment. The social environment can work as an obesogenic environment that pushes persons to make choices and decisions culturally perceived as normal and accepted even though they might not be healthy [32]. On the contrary, the physical environment does not modify individual habits but can directly affect adiposity risk as a biological response to exposure to chronic stress [33], endocrine-disrupting chemicals [34], or air pollution [35].
The findings of our study suggest that future research should focus on an even broader investigation of external as well as internal factors, which may have the potential to complement the mediators investigated in the current study to better explain why increased adiposity is more prevalent in groups with lower education. The identification of various pathways will help focus prevention activities on specific behaviors or characteristics and improve cardiometabolic health in the disadvantaged groups of the population.
The major strength of the present study is the complex approach to adiposity assessment, including several anthropometric and bioimpedance measures, and the investigation of a wide spectrum of potential individual mediators. Moreover, by analyzing and reporting results separately for men and women, the study acknowledges and accounts for potential gender variations in the observed relationships. However, there are some limitations of this study that should be mentioned. First, the study’s cross-sectional design does not allow causality evaluation; thus, the direction of the associations set in the multiple mediation model was constructed based on previous research evidence, and a reverse causation bias might occur. Second, the study sample only included a city-based population; thus, the study findings should not be generalized beyond the urban population. Third, investigated mediators were mostly self-reported; therefore, reporting bias, including underestimation, might occur. However, objectively measured data on these factors were not available, and questionnaire based for behaviors such as smoking, or alcohol consumption are widely accepted. Additionally, the version of FFQ used in the current study has not been previously validated in different study; however, the content has been developed in accordance with previous literature recommendations for FFQ development and utilization [16, 36].
Based on our findings, we conclude that educational disparities in adiposity and related mediators might differ by sex. The increased adiposity in women with lower educational levels is likely driven by dietary risky behaviors and lower income, but we did not observe a mediator which contributes to the inverse gradient between education and adiposity in men. However, our study identified sedentary behaviors as a risk factor possibly reducing the protective potential of higher educational levels in both sexes, with a higher magnitude in men. This finding suggests that reducing sedentary time should be sufficiently targeted in public health strategies to reduce the burden of increased adiposity in the population. Future studies should investigate a broader spectrum of potential mediators, including knowledge-related individual factors as well as components of the external social and physical environment.
