Loneliness, social integration, and incident dementia over 6 years: prospective findings from the English longitudinal study of ageing

Objectives: Social relationships are important for the maintenance of cognitive function at older ages, with both objective features of social networks and perceived social connections (loneliness) being relevant. There is limited evidence about how different aspects of social experience predict diagnosed dementia. Methods: The sample comprised 6,677 dementia-free individuals at baseline (2004) from the English Longitudinal Study of Ageing. Baseline information on loneliness, number of close relationships, marital status, and social isolation (contact with family and friends and participation in organizations) was analyzed in relation to incident dementia over an average 6.25 years using Cox regression, controlling for potential confounding factors. Results: Two hundred twenty participants developed dementia during follow-up. In multivariable analyses, dementia risk was positively related to greater loneliness (hazard ratio 1.40, 95% confidence interval 1.09-1.80, p = .008), and inversely associated with number of close relationships (p < .001) and being married (p = .018). Sensitivity analyses testing for reverse causality and different criteria for diagnosing dementia confirmed the robustness of these findings. There was no association with social isolation. Discussion: Dementia risk is associated with loneliness and having fewer close relationships in later life. The underlying mechanisms remain to be elucidated, but efforts to enhance older peoples' relationship quality may be relevant to dementia risk.