Loneliness during the COVID-19 pandemic: A potential risk factor for post-pandemic cognitive decline in older adults without dementia.

The COVID-19 pandemic has exacerbated loneliness and social isolation among older adults, raising concerns about their mental and physical well-being. While loneliness's adverse effects on health are well-documented, its specific impact on cognitive health during the pandemic remains under investigation. Objective: The aim of this study was to examine the association between loneliness during the COVID-19 pandemic and cognitive decline in cognitively unimpaired older adults by synthesizing evidence from primary studies. Methods: A comprehensive search strategy was employed across multiple databases, including MEDLINE (PubMed), CINAHL (EBSCO), PsycINFO (EBSCO), EMBASE, Scopus, AgeLine, and ProQuest, following PRISMA guidelines. Studies were selected to examine the association between loneliness and cognitive function in cognitively unimpaired older adults (aged ≥50 years) during the COVID-19 pandemic. Results: A total of eight studies were included from 1,384 search results, reviewing data from 10,449 cognitively unimpaired older adults. A total of six studies found significant associations between loneliness or social isolation and subjective cognitive decline (SCD). Only one study linked loneliness to lower objective cognitive performance. Notably, half of the studies considered key covariates, such as depression, which could mediate the relationship between loneliness and cognitive decline. Conclusion: Loneliness during the COVID-19 pandemic is linked to SCD in older adults, though objective evidence is limited. The pandemic underscored the long-term impact of social isolation on cognition and mental health, highlighting the need for standardized neuropsychological tools and key covariates in studies to identify those at risk.