Social Isolation as a Risk Factor for Dementia: Insights from Animal Model Studies

Social isolation (SI) and loneliness (perceived social isolation) are considered as risk factors for developing dementia, including Alzheimer's disease (AD), in the elderly population. Intriguingly, recent reports have shown a significant association of loneliness with a higher amyloid- β (Aβ) burden, suggesting that SI is linked to the pathophysiology of AD. Numerous studies, using rodents or other animal models have revealed diverse biological effects of SI, including induction of oxidative stress and activation of neuroinflammation. Furthermore, using transgenic mouse models of AD, recent investigations have shown that SI affects AD pathology, particularly the deposition of Aβ and neuroinflammation. However, it remains unclarified, by which mechanisms SI confers a significant risk for AD. In this narrative mini-review, I overview published studies on the pathobiological effects of SI in rodent models and discuss the mechanisms by which SI exacerbates AD pathology. Clarification of this issue has significant implications for the design of strategies for preventing cognitive impairment and dementia in the elderly population.