Social isolation associated with a high risk of subsequent dementia

Longitudinal studies have shown that social isolation was associated with a decrease in the volume of cognitive-related brain regions and was associated with an increased risk of subsequent dementia.

Of more than 460,000 participants UK BiobankSocial isolation at age 57 led to a 26% increase in the risk of dementia after 12 years, regardless of risk factors such as loneliness and depression, said Jianfeng Feng of Fudan University in Shanghai, China. The doctor and co-authors reported.

Researchers write that socially isolated individuals also had lower levels of gray matter in the temporal, frontal, and hippocampal areas. Neurology..

“People who reported high levels of social isolation were more likely to show significant differences in brain volume in areas that were also known to be associated with cognitive problems and the risk of dementia,” he said. University co-author Dr. Barbara Sahakian said. Statement from Cambridge, England.

“This is of great concern and suggests that social isolation may be an early indicator of an increased risk of dementia,” she added.

Recent studies have shown that Lonely elderly adult Those who were otherwise expected to be at relatively low risk were three times more likely to have dementia than those who were not alone. Middle-aged loneliness It is also associated with dementia and Alzheimer’s disease in later years.

However, few studies have investigated social isolation apart from loneliness.

“There is a difference between social isolation, which is an objective state of low social ties, and loneliness, which is a subjectively perceived social isolation,” said Edmund Rolls, co-author of the University of Warwick in the United Kingdom. The doctor says.

“Both have health risks, but by using an extensive multimodal data set from UK Biobank and working in an interdisciplinary way that links computational science and neuroscience, we are socially isolated rather than lonely. I was able to show that it is an independent risk factor for later dementia. “

“This is a serious but underestimated public health problem, as social isolation and loneliness have been rampant over the last few decades,” Rolls added. “Currently, behind the COVID-19 pandemic, there are impacts on social intervention and care, especially in the elderly.”

The survey enrolled 462,619 people with an average baseline age of 57 years at UK Biobank. 45.4% were male and 95.3% were white. Registration for the survey began in 2006 and data was collected until January 31, 2021.

At baseline, 41,886 (9%) said they were socially isolated, and 29,036 (6%) said they felt lonely.

Compared to controls, both isolated and lonely people had worse cognitive function after adjusting for age, gender, ethnicity, education, and income. Depressive symptoms were also significantly associated with cognitive function after adjusting for the same variables (P<0.001 all).

At an average of 11.7 years of follow-up, 4,998 people developed dementia of all causes. The incidence of dementia was 26% higher in those who reported social isolation (adjusted HR 1.26, 95% CI 1.15-1.37).

The adjusted HR for dementia associated with loneliness was 1.04 (95% CI 0.94-1.16), but 75% of this relationship was due to depressive symptoms.

Subgroup analysis showed that the relationship between social isolation and dementia was consistent between men and women. When analyzed by age, only socially isolated people in the elderly group (mean age 64.6 years, 43% of the sample) were significantly associated with dementia (adjusted HR 1.28).

A subset of 32,263 participants (mean age 63.5 years, 52% female) underwent neuroimaging on average 8.8 years after baseline. Of these, 2,371 (7%) reported social isolation and 1,503 (5%) said they were lonely. The amount of gray matter partially mediated the association between baseline social isolation and follow-up cognitive function.

Prevention of age-related neurodegenerative disease is central to many clinical studies of Alzheimer’s disease, said Lawrence Wally, a doctor of medicine at the University of Aberdeen, Scotland. Ancillary editorial.. “Elderly people living in social isolation are more likely to be lonely, but loneliness alone is not enough to increase the risk of dementia,” Whalley said.

Whalley pointed out that this study sets new challenges for dementia prevention.

“The first is to show that social isolation appears as a major factor leading to dementia and is not the result of cognitive impairment,” he writes. “The following is an intellectual task to uncover the substructure of social isolation and identify the factors most relevant to the risk of dementia.”

Feng et al. Admitted that UK Biobank participants have less self-reported health and are less likely to live alone than the general public. It is unclear how this affects the link between social isolation and loneliness and the risk of dementia.