Reducing socio-economic inequalities in all-cause mortality: a counterfactual mediation approach
Authors: Laine Jessica E , Baltar Valéria T , Stringhini Silvia , Gandini Martina , Chadeau-Hyam Marc , Kivimaki Mika , Severi Gianluca , Perduca Vittorio , Hodge Allison M , Dugué Pierre-Antoine , Giles Graham G , Milne Roger L , Barros Henrique , Sacerdote Carlotta , Krogh Vittorio , Panico Salvatore , Tumino Rosario , Goldberg Marcel , Zins Marie , Delpierre Cyrille ,   LIFEPATH Consortium, Alenius Harri , Avendano Mauricio , Baltar Valéria , Bartley Mel , Barros Henrique , Bochud Murielle , Carmeli Cristian , Carra Luca , Castagné Raphaele , Chadeau-Hyam Marc , Clavel-Chapelon Franç Oise , Costa Giuseppe , Courtin Emilie , Delpierre Cyrille , Donkin Angela , D'Errico Angelo , Dugué Pierre-Antoine , Elliott Paul , Fiorito Giovanni , Fraga Silvia , Garès Valérie , Gandini Martina , Giles Graham , Goldberg Marcel , Greco Dario , Hodge Allison , Karimi Maryam , Kelly-Irving Michelle , Karisola Piia , Kivimaki Mika , Krogh Vittorio , Laine Jessica , Lang Thierry , Layte Richard , Lepage Benoit , Mackenbach Johan , Marmot Michael , de Mestral Carlos , McCrory Cathal , Milne Roger , Muennig Peter , Nusselder Wilma , Panico Salvatore , Petrovic Dusan , Polidoro Silvia , Preisig Martin , Raitakari Olli , Ribeiro Ana Isabel , Ricceri Fulvio , Reinhard Erica , Robinson Oliver , Valverde Jose Rubio , Sacerdote Carlotta , Satolli Roberto , Severi Gianluca , Shipley Martin J , Stringhini Silvia , Tumino Rosario , Tieulent Joannie , Vaccarella Salvatore , Vergnaud Anne-Claire , Vineis Paolo , Vollenweider Peter , Zins Marie , Vineis Paolo 
Published: November 2019

Abstract

Background
Socio-economic inequalities in mortality are well established, yet the contribution of intermediate risk factors that may underlie these relationships remains unclear. We evaluated the role of multiple modifiable intermediate risk factors underlying socio-economic-associated mortality and quantified the potential impact of reducing early all-cause mortality by hypothetically altering socio-economic risk factors.

Methods
Data were from seven cohort studies participating in the LIFEPATH Consortium (total n = 179 090). Using both socio-economic position (SEP) (based on occupation) and education, we estimated the natural direct effect on all-cause mortality and the natural indirect effect via the joint mediating role of smoking, alcohol intake, dietary patterns, physical activity, body mass index, hypertension, diabetes and coronary artery disease. Hazard ratios (HRs) were estimated, using counterfactual natural effect models under different hypothetical actions of either lower or higher SEP or education.

Results
Lower SEP and education were associated with an increase in all-cause mortality within an average follow-up time of 17.5 years. Mortality was reduced via modelled hypothetical actions of increasing SEP or education. Through higher education, the HR was 0.85 [95% confidence interval (CI) 0.84, 0.86] for women and 0.71 (95% CI 0.70, 0.74) for men, compared with lower education. In addition, 34% and 38% of the effect was jointly mediated for women and men, respectively. The benefits from altering SEP were slightly more modest.

Conclusions
These observational findings support policies to reduce mortality both through improving socio-economic circumstances and increasing education, and by altering intermediaries, such as lifestyle behaviours and morbidities.