Subjective social position and cognitive function in a longitudinal cohort of older, rural South African adults, 2014–2019

BackgroundThe relationship between subjective social position (SSP) and cognitive ageing unclear, especially in low-income settings. We aimed to investigate the relationship between SSP and cognitive function over time among older adults in rural South Africa.MethodsData were from 3771 adults aged ≥40 in the population-representative ‘Health and Ageing in Africa: A Longitudinal Study of an INDEPTH Community in South Africa’ from 2014/2015 (baseline) to 2018/2019 (follow-up). SSP was assessed at baseline with the 10-rung MacArthur Network social position ladder. Outcomes were composite orientation and episodic memory scores at baseline and follow-up (range: 0–24). Mortality- and attrition-weighted linear regression estimated the associations between baseline SSP with cognitive scores at each of the baseline and follow-up. Models were adjusted for age, age2, sex, country of birth, father’s occupation, education, employment, household assets, literacy, marital status and health-related covariates.ResultsSSP responses ranged from 0 (bottom ladder rung/lowest social position) to 10 (top ladder rung/highest social position), with a mean of 6.6 (SD: 2.3). SSP was positively associated with baseline cognitive score (adjusted β=0.198 points per ladder rung increase; 95% CI 0.145 to 0.253) and follow-up cognitive score (adjusted β=0.078 points per ladder rung increase; 95% CI 0.021 to 0.136).ConclusionIndependent of objective socioeconomic position measures, SSP is associated with orientation and episodic memory scores over two time points approximately 3 years apart among older rural South Africans. Future research is needed to establish the causality of the observed relationships, whether they persist over longer follow-up periods and their consistency in other populations.

DISCERNING STATUS: SUBJECTIVE SOCIAL POSITION AND COGNITIVE HEALTH AMONG OLDER ADULTS IN RURAL SOUTH AFRICA

Rapid population aging in high absolute poverty settings, such as much of South Africa, demands new research on the social context factors that affect cognitive aging in these settings. We investigated the relationships between subjective social position within one’s village and cognitive function and impairment, with the rationale that psychosocial stress induced by low relative social position may affect cognitive aging outcomes independently of absolute socioeconomic conditions. Data were from the population-representative HAALSI study of 5,059 adults aged 40+ in rural Agincourt, South Africa. Subjective social position was assessed using the MacArthur Network social ladder, which asks respondents to indicate how high up a ladder they stand, relative to others, in their village. Cognitive function was a composite z-score of time orientation and word recall tests; scores ≤1.5 standard deviations (SD) below the mean indicated cognitive impairment. Twenty percent of those on the bottom rung had cognitive impairment, declining to 2% on the top rung. In regression models adjusted for age, sex, country of birth, education, literacy, marital status, employment, and asset-based household wealth, each ladder rung increase was associated with an 0.05 SD increase in cognitive z-score (95% CI: 0.04-0.06), and a 17% decrease in odds of cognitive impairment (OR=0.83; 95% CI: 0.79-0.88); these associations were greater in magnitude than those for years of education with these cognitive outcomes. Future work should examine if these relationships persist longitudinally, and investigate the mechanisms of these relationships, including village-level contextual factors that may contribute to subjective social position in this setting.