Summary Aim To investigate the independent associations of social isolation and loneliness with incident dementia and explore possible neurobiological mechanisms. Methods We used the UK Biobank cohort to establish Cox proportional hazards models with social isolation and loneliness as separate exposures. Demographic (sex, age and ethnicity), socioeconomic (education 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 measured at baseline were adjusted for. Voxel-wise whole-brain association analyzes were then used to identify gray matter volumes (GMV) associated with social isolation and loneliness. Partial least squares regression was performed to test the spatial correlation of GMV differences and gene expression using the Allen Human Brain Atlas. Results 462,619 participants were included (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 due to any cause. Social isolation was associated with a 1.26-fold increased risk of dementia (95% CI, 1.15-1.37) independently of several risk factors, such as loneliness and depression (i.e., full adjustment). However, the fully adjusted hazard ratio for loneliness-related dementia was 1.04 (95% CI, 0.94-1.16); and 75% of this relationship was attributable to depressive symptoms. Structural MRI data were obtained from 32,263 participants (mean age 63.5 years [SD 7.5]). Socially isolated individuals had lower GMV in temporal, frontal, and other regions (e.g., hippocampus). Mediation analysis showed that identified gray matter volumes (GMV) partially mediated the association between social isolation at baseline and cognitive function at follow-up. Lower gray matter volumes (GMV) related to social isolation were related to underexpression of genes that are downregulated in Alzheimer’s disease and genes that are 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. Brain structural differences related to social isolation, along with different molecular functions, also support associations of social isolation with cognition and dementia. Therefore, social isolation may be an early indicator of increased risk of dementia. |
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Social isolation is directly linked to changes in brain structures associated with memory, making it a clear risk factor for dementia, scientists have found.
- Social isolation is an independent risk factor for dementia.
- An interdisciplinary study shows that changes in brain structures associated with memory and cognitive function are directly related to social isolation.
- Data shows that socially isolated people are 26% more likely to develop dementia later in life.
- Implications for health and social assistance policy, following the COVID-19 pandemic.
- Social isolation is directly linked to changes in brain structures associated with memory, making it a clear risk factor for dementia, scientists have found.
Researchers from the University of Warwick, the University of Cambridge and Fudan University set out to investigate how social isolation and loneliness were linked to later dementia, using neuroimaging data from more than 30,000 participants in the data set. UK Biobank.
Socially isolated individuals had lower gray matter volumes in brain regions involved in memory and learning.
The study results are published in Neurology , the medical journal of the American Academy of Neurology, in an article titled "Associations of social isolation and loneliness with later dementia" by Shen, Rolls, Cheng, Kang, Dong, Xie, Zhao, Sahakian and Feng (doi: 10.1212/WNL.0000000000200583).
Based on data from the UK Biobank, an extremely large longitudinal cohort, the researchers used modeling techniques to investigate the relative associations of social isolation and loneliness with incident all-cause dementia. After adjusting for several risk factors (including socioeconomic factors, chronic diseases, lifestyle, depression, and APOE genotype), socially isolated people were shown to be 26% more likely to develop dementia.
Loneliness was also associated with later dementia, but that association was not significant after adjusting for depression, explaining 75% of the relationship between loneliness and dementia. Therefore, relative to the subjective feeling of loneliness, objective social isolation is an independent risk factor for later dementia. An additional subgroup analysis showed that the effect was prominent in those over 60 years of age.
Professor Edmund Rolls, a neuroscientist at the Department of Computer Science at the University of Warwick, said: “There is a difference between social isolation, which is an objective state of low social connections, and loneliness, which is perceived social isolation. subjectively.
“Both have health risks but, using the UK Biobank’s extensive multimodal data set and working in a multidisciplinary way linking computational sciences and neuroscience, we have been able to show that it is social isolation, rather than the feeling of isolation and 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.
“With the increasing prevalence of social isolation and loneliness in recent decades, this has been a serious but underappreciated public health problem. “Now, in the shadow of the COVID-19 pandemic, there are implications for interventions and care for social relationships, particularly in the older population.”
Professor Jianfeng Feng, from the Department of Computer Science at the University of Warwick, said: “We highlight the importance of an environmental approach to reducing the risk of dementia in older adults by ensuring they are not socially isolated. “During any future pandemic lockdowns, it is important that people, especially older adults, do not experience social isolation.”
Professor Barbara J Sahakian, from the Department of Psychiatry at the University of Cambridge, said: "Now that we know the risk to brain health and dementia from social isolation, it is important that the government and communities take action to ensure that people older people have communication and interactions with others on a regular basis.
