According to a study published in the July 12, 2023, online issue of Neurology®, the medical journal of the American Academy of Neurology, older people who have limited social contact may have a higher risk of brain volume loss and dementia compared to those with more frequent social contact.
This study does not conclusively prove that social isolation directly causes brain shrinkage; it only establishes an association between the two.
Study author Toshiharu Ninomiya, MD, PhD, from Kyushu University in Fukuoka, Japan, stated, “Social isolation is a growing problem for older adults. These findings suggest that providing support to help individuals initiate and maintain social connections may be beneficial for preventing brain atrophy and the development of dementia.”
The study included 8,896 participants with an average age of 73 who did not have dementia. They underwent MRI brain scans and health examinations. To assess social contact, participants were asked a single question: How often do you have contact with relatives or friends who do not live with you (e.g., meeting or talking on the phone)? The response options were every day, several times a week, several times a month, and seldom.
Individuals with the lowest amount of social contact had significantly lower overall brain volume compared to those with the highest social contact. The total brain volume, which includes white and grey matter, as a percentage of the total intracranial volume, was 67.3% in the lowest contact group and 67.8% in the highest contact group. Additionally, they exhibited lower volumes in areas of the brain, such as the hippocampus and amygdala, which are involved in memory and affected by dementia.
The researchers accounted for other factors that could impact brain volume, such as age, diabetes, smoking, and exercise.
Individuals who were socially isolated also had a greater number of small areas of brain damage known as white matter lesions compared to those with frequent social contact. The percentage of intracranial volume occupied by white matter lesions was 0.30 for the socially isolated group and 0.26 for the most socially connected group.
The study found that symptoms of depression partially explained the link between social isolation and brain volumes. However, symptoms of depression only accounted for 15% to 29% of this association.
Ninomiya stated, “While this study provides a snapshot in time and does not establish causation between social isolation and brain atrophy, previous studies have shown that exposing older individuals to socially stimulating groups halted or even reversed declines in brain volume and improved thinking and memory skills. Therefore, it is possible that interventions to reduce social isolation could prevent brain volume loss and subsequent dementia.”
It is worth noting that since the study only involved older Japanese individuals, the findings may not be generalizable to younger people or individuals of other ethnicities.
The study received support from the Japan Agency for Medical Research and Development and Suntory Holdings Limited.