Social isolation is associated with a significantly increased risk of dementia in older people, new research shows.
Results of a large, prospective, epidemiologic study show that individuals who reported feeling socially isolated had worse cognitive function at baseline than those who did not report social isolation and were 26% more likely to have dementia at follow-up.
MRI scans conducted nearly 9 years after study enrollment also showed that those who reported feeling socially isolated had lower gray matter volume (GMV) in areas of the brain linked to learning and memory.
There was no link between reported feelings of loneliness and dementia or GMV, which contradicts earlier findings.
The study, the latest to demonstrate a link between social isolation and cognitive function, suggests that efforts to decrease social isolation could reduce dementia risk in older adults.
“In our studies, the measures of social isolation can be reduced or prevented through ensuring individuals stay socially engaged with others through social visits, access to community activities, establishing friendships through hobbies and clubs,” study investigator Barbara J. Sahakian, DSc, FBA, FMedSci, professor of clinical neuropsychology, University of Cambridge, told Medscape Medical News.
“It is clear that if you are isolated, for example, living alone and not confiding in others, then you may be suffering from chronic stress through relying on only yourself, with no one to help you or with whom to discuss your problems,” she added.
The study was published online June 8 in Neurology.
Social Isolation vs Loneliness
Although social isolation has been shown to increase risk of cardiovascular disease and incident stroke, the link to dementia has been less clear. Studies have yielded inconsistent findings; one study showed that loneliness, but not social isolation, was associated with dementia risk.
To explore the issue, researchers examined data from the UK Biobank from 462,619 people from across the United Kingdom. The average age was 57 years.
Participants were asked whether they lived with others, had visits with friends or family at least once a month, and if they participated in social activities, such as clubs, meetings, or volunteer work, at least once a week. Those who answered no to at least two questions were considered socially isolated.
To measure loneliness, participants were asked if they often felt lonely and how often they confided in other people. Those who responded yes to the first question and reported confiding in others less than once a month were considered lonely.
Researchers also collected other personal information and MRI data and conducted tests to assess cognitive function.
At baseline, 9% reported being socially isolated, and 6% reported feeling lonely. Compared with control persons, isolated and lonely individuals had worse cognitive function at baseline after controlling for age, ethnicity, sex, education, and income.
After a mean follow-up of 11.7 years, 4998 participants developed dementia. The incidence was 26% higher among those who had reported being socially isolated (adjusted odds ratio, 1.26; 95% CI, 1.15 – 1.37).
Subgroup analysis revealed that social isolation was only significant in elderly participants (mean age, 64.6 years; adjusted hazard ratio [aHR], 1.28; 95% CI, 1.16 – 1.40) and in those with no depressive symptoms (aHR, 1.27; 95% CI, 1.15 – 1.41).
Although loneliness was significantly associated with dementia risk on univariate analysis, the link lost significance after adjusting for contributing factors, especially depressive symptoms, which reduced the significance by 75%.
MRI scans from about 32,263 participants conducted an average of 8.8 years after study onset revealed that those who reported higher levels of social isolation were more likely to have lower volumes of brain structures, including the medial temporal lobe, the hippocampus, the amygdala, the thalamus, and other areas associated with learning or thinking (P < .001).
Researchers also found that genes known to be downregulated in patients with Alzheimer’s disease were underexpressed in regions with lower gray matter volume associated with social isolation (P = .002).
An Important Contribution
In an accompanying editorial, Lawrence Whalley, MD, professor emeritus of mental health, University of Aberdeen, United Kingdom, notes the study’s data on brain volume and the identification of loneliness and social isolation as separate constructs are important contributions to the field.
“They distinguish the effects of social isolation from loneliness and show it is social isolation acting alone and not loneliness that increases the incidence of dementia,” Whalley writes.
“By itself, this is a useful conclusion, consolidating earlier work, and translates easily into community actions to address health concerns of old people living socially isolated lives,” Whalley adds.
A full list of funding sources is available in the original article. Sahakian receives funding from a Wellcome Trust Collaborative Award, and her research is conducted within the National Institute for Health and Care Research (NIHR) Cambridge Biomedical Research Centre and the NIHR MedTech and In Vitro Diagnostics Co-operative. Sahakian and Whalley have disclosed no relevant financial relationships.
Neurology. Published online June 8, 2022. Abstract