# The mediating role of chronic disease in socioeconomic inequalities in frailty: A longitudinal cohort study of older adults in Lausanne, Switzerland

## TL;DR

This study finds that chronic diseases like obesity and diabetes partly explain why people with lower socioeconomic status are more likely to become frail as they age.

## Contribution

The study quantifies the mediating role of specific chronic diseases in socioeconomic disparities in frailty using a longitudinal cohort.

## Key findings

- Socioeconomic disadvantage was linked to a 1.5–2.5-fold higher risk of frailty.
- Obesity and diabetes mediated up to 55% and 22%, respectively, of the socioeconomic-frailty association.
- Multimorbidity explained 21–39% of the association, while other chronic conditions showed minimal mediation.

## Abstract

Frailty is a major public health concern in aging populations. Socioeconomic disadvantage increases the risk of frailty, yet the mechanisms underlying this association remain unclear.

To examine the mediating role of chronic diseases in the longitudinal association between socioeconomic disadvantage and frailty.

Population-based cohort study.

Lausanne, Switzerland.

4731 community-dwelling adults aged 65–70 years at recruitment (2004, 2010, and 2014), followed for up to 16 years, as part of the Lausanne Cohort 65+.

None.

Socioeconomic disadvantage was assessed using indicators of education, occupation, income, health insurance subsidy, and financial strain. Frailty was measured using the Fried phenotype (unintentional weight loss, exhaustion, low physical activity, weakness, and slow walking speed). Chronic conditions (obesity, diabetes, hypertension, cardiovascular and respiratory disease, and multimorbidity [≥2 conditions]) were assessed at baseline using standardized self-reported physician diagnoses. Counterfactual mediation using Cox proportional hazards models estimated the proportion of the socioeconomic disadvantage–frailty association mediated by each condition.

Socioeconomic disadvantage was associated with a 1.5–2.5-fold higher risk of incident frailty. Obesity mediated 13–55% of this association, diabetes 11–22%, and multimorbidity 21–39%, whereas hypertension, cardiovascular, and respiratory disease showed minimal or no mediation.

Chronic diseases—particularly obesity and diabetes—partly explain the long-term impact of socioeconomic disadvantage on frailty, underscoring stark inequities in healthy aging. Early detection and management of these conditions in socioeconomically vulnerable older adults, alongside population-level prevention and efforts to address adverse socioeconomic conditions as root causes, could help reduce these inequalities.