Social
Social isolation and cognitive function and decline in a population-based longitudinal study of aging in India, overall and by education Peiyao Zhu* Peiyao Zhu Emma Nichols Alden L. Gross Jinkook Lee Lindsay C. Kobayashi
Social isolation is a risk factor for dementia, while education is the strongest known protective factor against dementia. Education is thought to enhance cognitive reserve, although a large share of older adults in low- and middle-income countries lack formal education and may be disproportionately vulnerable to additional cognitive risk factors. We estimated the associations between social isolation and cognitive function at baseline and rate of change over time among older adults in India, and whether these associations are stronger among those without formal education. We analyzed baseline data from 3,654 adults (mean age: 69.5) in the population-based LASI-DAD cohort (2017–2019) and follow-up data from 2,291 adults (2022–2024; mean follow-up: 4.2 years). Social isolation at baseline was measured using a 5-point index including living arrangements, social organization participation, and frequency of contact with friends/relatives. General and domain-specific cognitive function (memory, orientation, executive function, verbal fluency) scores were derived at both waves from the Harmonized Cognitive Assessment Protocol. We used a multivariable-adjusted joint modeling approach linking mixed-effects linear regression with survival analysis to account for potential selection bias due to differential mortality and evaluated interactions between social isolation and formal education (yes vs. no). Nearly half of our sample had no formal education (49%). Greater social isolation was associated with lower baseline general cognitive scores (β=-0.04 SD units; 95% CI: -0.06, -0.01, per 1-point increase in isolation), memory (β=-0.06; 95% CI: -0.08, -0.03), and language (β=-0.04; 95% CI: -0.07, -0.01), but not subsequent rates of decline. We found no interaction between social isolation and education in cognitive outcomes. Social isolation is a modifiable risk factor for cognitive function among older adults in India, with similar associations regardless of formal education.