Leo Sher, M.D.

A research article, “Psychological and neurobiological mechanisms involved in the relationship between loneliness and cognitive decline in older adults” has been published in a recent issue of Brain, Behavior, and Immunity (1).

The authors investigated several research objectives: First, they sought to identify neurobiological and psychological pathways that may account for the relationship between loneliness and decline across several cognitive domains. These pathways included depressive symptoms, total gray matter volume, and conditional analyses of pro-inflammatory cytokines and brain-derived neurotrophic factor (BDNF) expression. Second, it examined loneliness as a predictor of mild cognitive impairment (MCI) and Alzheimer’s disease (AD). Third, it sought to determine whether the relationship between loneliness and cognitive decline is sex-specific in older adults.

Longitudinal data were collected from 2130 Rush Memory and Aging Project (RMAP) participants. RMAP is part of a larger ongoing multisite research project at Rush University, Chicago, Illinois. In 1997, RMAP began recruiting older women and men (age 65+) with no evidence of dementia at time of enrollment. Participants underwent annual cognitive and psychological assessments and neuroimaging procedures every year. BDNF gene expression was measured in the dorsolateral prefrontal cortex, cytokines were measured in serum, and the final consensus clinical diagnosis was identified at the time of death. Participants were largely women (73 %), and Caucasian (93 %). The average education was 14.93 (SD = 3.34) years. The average age at baseline was 80.05 (SD = 7.57) years.

The study showed that gray matter volume and depressive symptoms partially mediated the relationship between loneliness and cognitive decline. There was a significant interaction between loneliness and BDNF expression in relation to cognitive decline. Higher levels of BDNF expression were associated with slower decline in semantic memory and visuospatial ability. The current study also found that higher levels of loneliness were positively associated with the incidence of AD and other dementias.

In summary, this study indicated that loneliness increases the probability of AD incidence, BDNF reduces the adverse impact of loneliness on cognition, and the relationship between loneliness and cognitive decline can be explained by physiological and psychological mechanisms. The results of this study support the growing data showing that the consequence of loneliness goes beyond the feeling of being isolated.

Reference

1. Dabiri S, Mwendwa DT, Campbell A. Psychological and neurobiological mechanisms involved in the relationship between loneliness and cognitive decline in older adults. Brain Behav Immun. 2024 Feb;116:10-21. doi: 10.1016/j.bbi.2023.11.034. Epub 2023 Nov 24.