Background We 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.
Methods In 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.
Results Less-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.
Conclusions In men, a DS mechanism substantially contributes to the educational class gradient in allostatic load.
- Social inequalities
- Epidemiological methods
- Epidemiology of cardiovascular disease
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Correction notice This article has been corrected since it first published. Affiliation 5 has been corrected to 'Catalan Department of Health'.
Contributors GV, FK and MMF conceived the research question and drafted the manuscript together with BH and HF. GV conducted the statistical analyses. KK, TZ and SB are guarantors of the MORGAM/BiomarCaRE database. HT-P, SuS, VS, BT, FK, MMF, StS, GC, LI and LP are Principal Investigators of the cohorts included in the current analyses. HT-P, SuS, VS, BT, ADiC, StS, GC, LI, LP, MB, RDP, KK, TZ and SB actively contributed to the interpretation of the results and made critical revision of the manuscript drafts. All authors read and approved the final version of the manuscript.
Funding The BiomarCaRE Project is funded by the EU Seventh Framework Programme (FP7/2007–2013) under grant agreement HEALTH-F2-2011-278913. The activities of the MORGAM Data Centre have also been sustained by recent funding from EU FP7 project CHANCES (HEALTH-F3-2010-242244). A part of the biomarker determinations in the population cohorts was funded by the Medical Research Council London (G0601463, identification No. 80983: Biomarkers in the MORGAM Populations).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval All participating studies adhered to the Declaration of Helsinki and are responsible for ethical approval and patient consent, according to local rules at the time of study enrolment. For different study populations, the list of approvals is the following: (study name, Ethics Committee name, approval ID): Northern Sweden, Research ethic Committee of Umea University, 2012–280–32M; FINRISK 1997, Ethics Committee at National Public Health Institute of Finland, 38/96; PRIME-Northern Ireland, Office for Research Ethics Committees Northern Ireland, 06/NIR02/107; MONICA/KORA Augsburg, Ethik-Kommision Bayerische Landesarztekammer, 05004; MONICA-Brianza, Comitato Etico Azienda Ospedaliera San Gerardo - Monza, 192/2005; MATISS Study (Latina), Comitato Etico Istituto Superiore di Sanità, PRE/96/06; Moli-Sani study, Comitato Etico Università Cattolica del Sacro Cuore – Roma, Prot.Pdc.P99 (A. 931/03-138-04)/CE/2004. MONICA-Catalonia: Director/Board of the Institute of Health Studies, ID not assigned. Scottish Heart Health Extended Study (SHHEC): Tayside Health Board Dundee District, DM/CL/20.
Provenance and peer review Not commissioned; externally peer reviewed.
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