Japanese study reveals that social isolation is linked to brain shrinkage in the elderly.

Previously, a lack of social contact and the subsequent diminished mental stimulation have been associated with the onset of dementia. Nevertheless, this new study by Japanese scientists seeks to shed light on the effects of social isolation on the brain's structure.

Participants in this study were asked about the frequency with which they contacted friends and relatives who did not live with them, factoring in the frequency of both in-person meetings and telephone conversations.

The responses were then analyzed and compared with MRI scans. The evidence showed that the connection between minimal social interaction and a decline in brain size among elderly Japanese people remains clear, even after factoring in other potential influences such as weight, tobacco use, alcohol consumption, and the presence of diabetes.

In the group with the least social interaction, the average brain volume was 67.3%, while in the most socially active group, it was slightly larger at 67.8%. The same pattern was seen in individual areas of the brain—the hippocampus and the amygdala—which are vital for memory processes and strongly linked to dementia.

The researchers also discovered that those who are socially isolated tend to have more small areas of brain damage, known as white matter changes, compared to those with frequent social contact. The intracranial volume, which includes these white matter changes, measured 0.30% in the socially isolated group and 0.26% in the most socially involved group.

This suggests a lack of social interaction may accelerate the natural brain aging process, including a gradual decrease in overall volume.

The findings of this study, published in the Neurology journal, suggest that personality changes can occur in individuals suffering from loss of brain volume. If a person becomes prone to apathy due to brain volume loss, decreased social interaction might be an effect of this condition, rather than a cause.

The researchers also contend that depression, known to be associated with brain shrinkage, may partially account for the correlation between social isolation and reduced brain volume. However, depression symptoms only explain a small fraction of this relationship.

Dr Toshiharu Ninomiya, the study's leading author from Kyushu University in Japan, emphasizes that while the study does not definitively conclude that social isolation leads to brain atrophy, other research indicates that social engagement among the elderly may halt, or even reverse, brain volume decline.

He underscored that "social isolation is becoming an increasingly prevalent issue among older individuals" and that "these results suggest that aiding individuals in establishing and sustaining social relationships may be advantageous in preventing brain atrophy and the onset of dementia."