Social isolation is directly linked to later dementia

Summary: Social isolation has been directly linked to structural changes in brain areas associated with memory and cognitive functioning. Researchers report that socially isolated people are 26% more likely to develop dementia later in life.

Source: University of Warwick

Social isolation is directly linked to changes in brain structures linked to memory, making it a clear risk factor for dementia, scientists have found.

To examine how social isolation and loneliness are linked to later dementia, researchers from the University of Warwick, the University of Cambridge and Fudan University used neuroimaging data from more than 30,000 participants in the UK Biobank data set. Socially isolated individuals have been found to have lower gray matter volumes in brain regions involved in memory and learning.

The results of the study will be published online in neurology.

Based on data from the UK Biobank, an extremely large longitudinal cohort, researchers used modeling techniques to examine the relative associations of social isolation and loneliness with the onset of all-cause dementia.

After adjusting for various risk factors (including socioeconomic factors, chronic illness, lifestyle, depression and APOE genotype), socially isolated individuals were shown to have a 26% increased likelihood of developing dementia.

Loneliness was also associated with later dementia, but this association was not significant after adjusting for depression, explaining 75% of the relationship between loneliness and dementia. Therefore, objective social isolation relative to the subjective feeling of loneliness is an independent risk factor for later dementia. Further subgroup analyzes showed that the effect was clear in those over 60 years of age.

Professor Edmund Rolls, a neuroscientist at the University of Warwick’s Computer Science Department, said: “There is a difference between social isolation, an objective state of low social connection, and loneliness, a subjectively perceived social isolation.

“Both have health risks, but by using the UK Biobank’s extensive multimodal dataset and the multidisciplinary work linking computational science and neuroscience, we were able to show that it is about social isolation rather than feelings of loneliness, which is an independent risk factor.” for later dementia. This means it can be used as a predictor or biomarker of dementia in the UK.

“Given the growing prevalence of social isolation and loneliness in recent decades, this has been a serious but underappreciated public health issue. Now, in the shadow of the COVID-19 pandemic, there are implications for interventions in social relationships and caregiving — particularly in the older population.”

Professor Jianfeng Feng, from the University of Warwick’s Department of Computer Science, said: “We emphasize the importance of an environmental approach to reducing the risk of dementia in older adults by ensuring they do not become socially isolated. During future pandemic lockdowns, it is important that individuals, particularly older adults, do not experience social isolation.”

Professor Barbara J. Sahakian, from the University of Cambridge’s Department of Psychiatry, said: “Now that we know the risk of social isolation for brain health and dementia, it is important that government and communities take action to ensure that older people being able to communicate and regular interactions with others.”

About this social isolation and news from dementia research

Author: Sheila Kiggins
Source: University of Warwick
Contact: Sheila Kiggins – University of Warwick
Picture: The image is in the public domain

Original research: Closed access.
“Associations of social isolation and loneliness with later dementia” by Edmund Rolls et al. neurology

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abstract

Associations of social isolation and loneliness with later dementia

objective

To examine the independent associations of social isolation and loneliness with onset dementia and to explore the potential neurobiological mechanisms.

methods

We used the UK Biobank cohort to construct Cox proportional hazard models with social isolation and loneliness as separate exposures. Demographic (gender, age, and race), socioeconomic (educational level, household income, and Townsend Deprivation Index), biological (BMI, APOE Genotype, diabetes, cancer, cardiovascular disease, and other disabilities), cognitive (processing speed and visual memory), behavioral (current smoking, alcohol consumption, and physical activity), and psychological (social isolation or loneliness, depressive symptoms, and neuroticism) factors were measured Start of studies have been adjusted. Then, voxel-by-voxel brain-wide association analyzes were used to identify the gray matter volumes (GMV) associated with social isolation and loneliness. A partial least squares regression was performed to test the spatial correlation of GMV differences and gene expression using the Allen Human Brain Atlas.

Results

We enrolled 462,619 participants (mean age at baseline 57.0 years [SD 8.1]). With a mean follow-up of 11.7 years (SD 1.7), 4,998 developed dementia from any cause. Social isolation was associated with a 1.26-fold increased risk of dementia (95% CI, 1.15–1.37) independent of various risk factors, including loneliness and depression (i.e. full adjustment). However, the fully adjusted hazard ratio for dementia-related loneliness was 1.04 (95% CI, 0.94-1.16); and 75% of this relationship was attributable to depressive symptoms. Structural MRI data were collected from 32,263 participants (mean age 63.5 years [SD 7.5]). Socially isolated individuals had lower GMVs in temporal, frontal, and other (eg, hippocampal) regions. The mediation analysis showed that the identified GMVs partially mediated the association between social isolation at baseline and cognitive function at follow-up. Lower GMVs associated with social isolation were associated with underexpression of genes that are downregulated in Alzheimer’s disease and genes involved in mitochondrial dysfunction and oxidative phosphorylation.

Conclusion

Social isolation is a risk factor for dementia that is independent of loneliness and many other covariates. Structural differences in the brain related to social isolation associated with different molecular functions also support the associations of social isolation with cognition and dementia. Social isolation can thus be an early indicator of an increased risk of dementia.