Does education lower allostatic load? A co-twin control study

Abstract

Many studies have found that education is associated with better health, but the causal basis of this association is unclear. The current study used a co-twin control design to examine if differences in years of education within twin pairs predict allostatic load. The strength of this design is that it controls for genetic and other familial confounds shared between twins. The sample consisted of 381 twins (with 292 twins from 146 complete pairs; mean age=57; 61% female) who participated in the biomarker project of the Midlife Development in the United States (MIDUS) study. Individual-level analyses showed a significant, negative association between years of education and allostatic load, but this association was explained entirely by familial influences shared between twins. The results of this study suggest that schooling does not itself protect against allostatic load.

Parental socioeconomic position and midlife allostatic load: a study of potential mediators

“…Aside from the smaller sample size of the present study, the discrepancy with the present findings could result from cohort effects, reflecting generational differences in the effect of education on AL. In a recent twin study [ 66 ], the within-pair effect of different educational levels on AL was found to be non-significant in monozygotic twins. While the sample age range (37–86 years) was considerably broader than that of the present study, again limiting comparability, the finding highlights the possibility of genetic or environmental confounding.…”

A systematic review of allostatic load in relation to socioeconomic position: Poor fidelity and major inconsistencies in biomarkers employed

“…[26][27][28] Rather than summing individual biomarkers, four studies summed the proportion of high risk markers by biological system. [29][30][31][32] For example, if a person was above the high-risk cutoff for two out of four cardiovascular biomarkers, they would receive a score of 0.5 for this system. This approach was used in studies analysing the Midlife in the US study where over 20 biomarkers were combined from five or more biological systems to calculate an AL index.…”

“…[33][34][35][36] Two studies included the same 24 biomarkers from the immune response, HPA axis, and cardiovascular, metabolic, respiratory and parasympathetic nervous systems. 31,32 All remaining 20 studies used different sets of biomarkers to calculate AL.…”

Educational attainment and allostatic load in later life: Evidence using genetic markers

“…Despite the growing body of replications over time and across different socio-political and economic contexts, evidence for a causal effect of education on biomarkers is much more limited. To our knowledge, the only study attempting to explore the association between education and AL using a co-twin control design failed to find causality (Hamdi et al, 2016).…”