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. Combining data from ongoing aging studies and the published literature, we provided the largest meta-analysis on the association between loneliness and dementia ( = 21 samples, = 608,561) and cognitive impairment ( = 16, = 103,387). Loneliness increased risk for all-cause dementia (HR = 1.306, 95% CI [1.197,1.426]), Alzheimer's disease (HR = 1.393, 95% CI [1.290,1.504]; = 5), vascular dementia (HR = 1.735, 95% CI [1.483,2.029]; = 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. Results underscored the importance to further examine type/sources of loneliness and cognitive symptoms to develop effective interventions that reduce the risk of dementia.