The Long-Term Public Health Impact of Social Distancing on Brain Health: Topical Review

Abstract

Social distancing has been a critical public health measure for the COVID-19 pandemic, yet a long history of research strongly suggests that loneliness and social isolation play a major role in several cognitive health issues. What is the true severity and extent of risks involved and what are potential approaches to balance these competing risks? This review aimed to summarize the neurological context of social isolation and loneliness in population health and the long-term effects of social distancing as it relates to neurocognitive aging, health, and Alzheimer’s disease and related dementias. The full scope of the underlying causal mechanisms of social isolation and loneliness in humans remains unclear partly because its study is not amenable to randomized controlled trials; however, there are many detailed experimental and observational studies that may provide a hypothesis-generating theoretical framework to better understand the pathophysiology and underlying neurobiology. To address these challenges and inform future studies, we conducted a topical review of extant literature investigating associations of social isolation and loneliness with relevant biological, cognitive, and psychosocial outcomes, and provide recommendations on how to approach the need to fill key knowledge gaps in this important area of research.

Association of Loneliness With 10-Year Dementia Risk and Early Markers of Vulnerability for Neurocognitive Decline

“…On the one hand, if we consider loneliness as an early symptom of neurodegeneration, the present findings may reflect the earliest manifestations of cortical β-amyloid 14 and tau 15 accumulation in brain areas that both are affected early in the course of ADRD and are involved in the perception of loneliness and other neurobehavioral functions. 23 On the other hand, if loneliness is mainly a causal factor in cognitive decline, the present findings may be indicative of loneliness driving (or compounding) vascular, neuroendocrine, inflammatory, and cytotoxic injury biological pathways that have been proposed to be specific to the distress of loneliness 21 or increased functional communication in neural systems implicated in generating one's perception of loneliness (e.g., the default mode network). 23 Regardless, although the present study is observational, it supports an upstream contributory role for loneliness given that participants without dementia were followed up for 10 years, which is longer than might typically be expected for dementia to develop if mild cognitive or neurobehavioral symptoms were present due to underlying ADRD pathologic changes.…”

Mediterranean Diet Reduces Social Isolation and Anxiety in Adult Female Nonhuman Primates

“…Taken together, diet composition may impact infectious disease progression—exacerbation by the Western diet or amelioration by the Mediterranean diet—through both behavioral and inflammatory pathways. Thus, dietary intervention may mitigate some of the deleterious health effects of social isolation and inflammation in COVID-19 and perhaps other infectious diseases [ 97 , 98 ].…”

Changes in Loneliness, BDNF, and Biological Aging Predict Trajectories in a Blood-Based Epigenetic Measure of Cortical Aging: A Study of Older Black Americans

“…Of course, loneliness often leads to depression, making it difficult to distinguish between the two as risk factors. There is, however, a growing consensus that the two are conceptually distinct constructs that can be distinguished clinically [ 35 ] and statistically [ 36 , 37 ]. Further, evidence suggests that they have distinctive brain circuitry [ 10 , 11 , 37 ] and that they exercise independent effects as risk factors for cognitive decline and dementia [ 28 , 36 , 38 ].…”