Socioeconomic inequalities in functional ageing trajectories in England and Canada: A comparative longitudinal cohort study

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BACKGROUND: Cross-country comparisons can provide valuable insights into the societal and policy contexts that shape socioeconomic inequalities in ageing. However, longitudinal comparative research in this area is scarce. We therefore examined associations between socioeconomic conditions and functional ageing trajectories in a longitudinal comparison between England and Canada. METHODS AND FINDINGS: In this longitudinal cohort study, data were drawn from the English Longitudinal Study of Ageing (ELSA, 2012-2023, N = 8511, 55% women, aged 50-85 years at baseline) and the Canadian Longitudinal Study on Aging (CLSA, 2012-2021, N = 22,605, 49% women, aged 50-85 years at baseline). Associations between total household wealth and physical functioning (gait speed, grip strength, chair stands, lung function, self-rated hearing, self-rated eyesight, mobility difficulties, and difficulties performing activities of daily living) were examined within each cohort using mixed-effects models, with additional adjustment for chronic conditions, weight status, health behaviours, and social connections. In each cohort, less wealth was associated with a poorer level of functioning across outcomes, and a greater decline in mobility and the ability to perform activities of daily living with age. In ELSA, wealthier individuals experienced a steeper decline in gait speed compared to their less wealthy counterparts, although their level remained higher throughout the follow-up period. In CLSA, wealthier individuals had a steeper decline in chair rise performance and self-rated eyesight compared to less wealthy individuals. Wealth inequalities in the level of functioning were generally greater in ELSA than in CLSA, especially for gait speed (years of functioning lost at age 60 = 15, 95% CI [12.2, 17.8] versus 9, 95% CI [8.6, 9.4]) and difficulties with basic activities of daily living (20, 95% CI [19.5, 20.4] versus 9, 95% CI [8.6, 9.4]). There were some significant wealth by sex interaction effects, such that women with the least wealth had more difficulties with mobility, activities of daily living, and hearing than men with the least wealth, but better lung function. Associations between wealth and functional outcomes were attenuated but persisted after adjustment for chronic conditions, weight status, health behaviours, and social connections. Limitations include the focus on socioeconomic conditions in adulthood and the inability to examine the contribution of other important factors to the observed associations, such as access to private healthcare. CONCLUSIONS: Socioeconomic inequalities in functional ageing are apparent in England and Canada, are larger in England than in Canada, and are not fully explained by common risk factors. These findings suggest that multilevel approaches, combining individual-level interventions with structural measures, are required to address socioeconomic inequalities and cross-country differences in functional ageing. Variation in wealth associations by sex suggests that approaches to reducing socioeconomic inequalities in functional health should account for potential sex differences.

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