A meta-analysis of loneliness and risk of dementia using longitudinal data from >600,000 individuals

Loneliness is one critical risk factor for cognitive health. Here we combined data from ongoing aging studies and the published literature and provide the largest meta-analysis on the association between loneliness and dementia (k = 21 samples, N = 608,561) and cognitive impairment (k = 16, N = 103,387). Loneliness increased the risk for all-cause dementia (hazard ratio (HR) 1.306, 95% confidence interval (CI) 1.197–1.426), Alzheimer’s disease (HR 1.393, 95% CI 1.290–1.504; k = 5), vascular dementia (HR 1.735, 95% CI 1.483–2.029; k = 3) and cognitive impairment (HR 1.150, 95% CI 1.113–1.189). The associations persisted when models controlled for depression, social isolation and/or other modifiable risk factors for dementia. The large heterogeneity across studies was partly due to differences in loneliness measures and ascertainment of cognitive status. The results underscore the importance to further examine the type or sources of loneliness and cognitive symptoms to develop effective interventions that reduce the risk of dementia.