Social isolation—and the loneliness that often comes with it—is a growing concern around the globe. Even before the lockdowns of the pandemic, the American Psychological Association had linked the effects of loneliness and isolation to everything from depression, poor sleep quality, and impaired executive function to accelerated cognitive decline, poor cardiovascular function, and impaired immunity at every stage of life.

But new research on older people has found an association between social isolation and lower brain volume, the latter of which suggests neurodegeneration that may result in dementia or Alzheimer’s disease.

The Research

A team of scientists from Kyushu University created a study comprised of 8,896 dementia-free participants with an average age of 73 who were living in a community setting in Japan. The goal was to “evaluate the association between low frequency of social contact and the volumes of various brain regions, and to assess the extent to which depressive symptoms mediate these relationships from a large population-based multisite cohort study.”

The participants underwent brain MRI scans and a comprehensive health examination, including questions about frequency of contact with non-cohabiting friends and relatives. Here are some of the highlights from the results:

• White and gray brain matter of those with the LEAST social contact occupied 67.3% of the available intracranial volume.

• White and gray brain matter of those with the MOST social contact occupied 67.8% of the available intracranial volume.

• A reduction in brain volume affected areas linked to memory and dementia, such as the hippocampus and amygdala. (The hippocampus is a brain region believed to be associated with Alzheimer’s.)

• The temporal lobe, occipital love, and cingulum were also reduced.

• Depression was a contributing factor but only accounted for 15% to 29% of the connection between social isolation and brain volumes.

• The most socially isolated people had a higher amount of white matter lesions that indicate brain damage.

Other Factors That May Reduce Brain Volume

Although the study shows an association between social isolation and lower brain function, it doesn’t establish a causal link. 

“What this paper adds [to previous research findings] is assessment of brain volumes through scanned measurements, which are linked to cognitive function,” explains Dr. Roseanne Freak-Poli, an epidemiologist from Monash University in Australia, who was not involved in the current study. “This paper gives an understanding of how the structure of the brain may be negatively influenced by social isolation. It is important to acknowledge that other factors associated with social isolation may also enact a reduction in brain volume. My prior research identified that unresolved and prolonged grief is associated with smaller volume and poor performance on cognitive tests.”

Another possible mechanism contributing to the findings of the current study?

Professor Barbara Sahakian, a University of Cambridge specialist in Alzheimer’s, who was not involved in the study but who has also published research on the link between brain volume and cognitive function, says that their own study “found a link between the lower grey matter volumes and specific genetic processes that are involved in Alzheimer’s.”

Regardless of the causal link, it’s important to note that once cognitive loss begins to occur, it may launch a downward spiral. People may find social contact difficult, even embarrassing, as they have struggle to remember names, faces, and previous conversations, leading them to withdraw from social contact even more, which may then accelerate cognitive decline.

The results of the study were published in the July 12, 2023 edition of the journal Neurology.

MBJ

Wendy Burt-Thomas writes about the brain, mental health and parenting.

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