Decomposing the educational gradient in allostatic load across European populations. What matters the most: differentials in exposure or in susceptibility?

Abstract

BackgroundWe investigate whether socially disadvantaged individuals are more susceptible to the detrimental effects of smoking and alcohol intake on allostatic load (AL), a marker of physiological ‘wear and tear’, resulting from adaptation to chronic stress.MethodsIn a cross-sectional analysis, 27 019 men and 26 738 women aged 35–74 years were identified from 21 European cohorts in the BiomarCaRE consortium. We defined three educational classes (EDs) according to years of schooling and an AL score as the sum of z-scores of eight selected biomarkers from the cardiovascular, metabolic and inflammatory systems. We used the Oaxaca-Blinder decomposition to disentangle the ED gradient in AL score into the differential exposure (DE, attributable to different distribution of smoking and alcohol intake across EDs) and the differential susceptibility (DS, attributable to a different effect of risk factors on AL across EDs) components.ResultsLess-educated men (mean AL difference: 0.68, 95% CI 0.57 to 0.79) and women (1.52, 95% CI 1.40 to 1.64) had higher AL scores. DE accounted for 7% and 6% of the gradient in men and women, respectively. In men, combining smoking and alcohol intake, DS accounted for 42% of the gradient (smoking DS coefficient=0.177, 26% of the gradient; alcohol DS coefficient=0.109; 16%, not statistically significant). DS contribution increased to 69% in metabolic markers. DS estimates were consistent across age groups, irrespective of comorbidities and robust to unmeasured confounding. No DS was observed in women.ConclusionsIn men, a DS mechanism substantially contributes to the educational class gradient in allostatic load.

Understanding health inequalities in Wales using the Blinder-Oaxaca decomposition method

“…Our findings therefore align with long established linkages between income and health and well-being (27)(28)(29)(30), and also with continued contemporary trends in self-reported health across Europe surrounding income (18,19) and in North America surrounding education (16,31). In addition, our findings support empirically derived evidence indicating the significant impact education (32) and income (17, 33) have on general health. However, the work of Sinha et al (34) indicates that there are potentially better indicators of poor health than income, and that tackling persistent deprivation in dimensions such as housing conditions and social isolation may be more fruitful.…”

Roles of allostatic load, lifestyle and clinical risk factors in mediating the association between education and coronary heart disease risk in Europe

“…In this prospective cohort study, we found evidence for the effect of differential exposure to AL on CHD incidence. As differential susceptibility in men was found in our companion paper to have a predominant role in the accumulation of AL in low educational classes, 14 further investigation of AL-related risk factors is needed. Meanwhile, any preventive action aiming to control factors linked to the disproportionate exposure to excess AL may help to reduce CHD morbidity, in particular among those with lower education.…”

“…In the same populations, we previously found that the educational gradient in AL in men was largely attributable to differential susceptibility to behavioural factors. 14 In particular, being a never smoker or having moderate alcohol intake was less protective in terms of AL accumulation in less educated men compared with their more educated counterparts. In women, the educational gradient in AL remained largely unexplained by both differential exposure and susceptibility to the same behavioural factors.…”

“…Indeed, we recently disentangled the contribution of lifestyle factors to the educational class gradient in AL in terms of differential exposure and susceptibility . 14 Following on this work, based on the same 21 European population-based cohorts, we aim to examine this second pathway, disentangling the contribution of differential exposure and susceptibility to AL and other mediators in CHD educational gradients applying modern counterfactual mediation models.…”