Loneliness leads to first stages of dementia
In apparently healthy over 65s, loneliness can have a potentially disastrous effect on the brain. Neurologists at the University of Harvard published about this in JAMA Psychiatry. The researchers discovered that loneliness stimulates the accumulation of amyloid plaques, and these amyloid plaques cause dementia.
The researchers did scans of the brains of 79 healthy men and women aged between 65 and 90, which enabled them to see the extent of amyloid plaque accumulation in their brain cells. In people who have Alzheimer's - which is the cause of dementia in 60-70 percent of all cases - brain cells die off because there are too many of the amyloid plaques.
The researchers also got the participants to fill out standard questionnaires on loneliness, depression and anxiety.
The lonelier the participants were, the more plaques the researchers found in their brains. Even when the researchers had filtered out the effects of other factors such as age, income, social network, depression and anxiety, the relationship was still there.
Brain cells make apolipoprotein E, a protein that transports cholesterol into brain cells. Quite a few people have genes that predispose them to making an over enthusiastic variant of apolipoprotein E. It's called ApoE4, and this variant increases the likelihood of developing Alzheimer's. The likelihood of loneliness leading to dementia was even higher in this group than in the people with better genes.
The researchers are aware that the relationship they discovered could be interpreted in various ways. "Loneliness or other subtle impairments in social-emotional perception or behavior could arise in preclinical Alzheimer's disease due to amyloid-related alterations in neural activity at a local or network level," they wrote. The plaques they found could actually be the cause of the feelings of loneliness. The researchers are more in favour of the alternative explanation - that loneliness speeds up the formation of plaques.
"It is also possible that the subjective experience of loneliness or detachment may promote amyloid accumulation, or there may be dynamic and reciprocal effects over time," they wrote. "Numerous epidemiological studies have established that antecedent social and psychosocial factors, including loneliness, are related to adverse outcomes such as depression, cognitive decline, functional impairment, and earlier mortality in older people."
"Social disengagement, manifesting as low numbers of social ties, contacts, and group activities, has been associated with cognitive decline in population-based studies of older people, even in those individuals with relatively high baseline cognitive and functional status."
"Many studies have also found independent effects on long-term cognition for more qualitative social and socio-emotional constructs such as emotional support, negative social interactions, and loneliness."
JAMA Psychiatry. 2016;73(12):1230-7.
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