People who are lonely are twice as likely
to develop Alzheimer's disease, a large US study has suggested.
The findings come from a study of more
than 800 elderly patients, who were followed over a four-year
Social isolation has already been shown
to be linked to dementia but this is the first time researchers
have looked at how alone people actually felt.
Writing in Archives of General Psychiatry,
the researchers said the reason for the link was not yet
Study leader Professor Robert Wilson
and colleagues assessed participants loneliness by asking
people to rate from one to five whether they agreed with
certain statements related to loneliness on an annual
Questions posed to those being studied
included "I experience a general sense of emptiness" and
"I often feel abandoned".
People in the study were also assessed
for signs of dementia and Alzheimer's disease.
And autopsies were carried out on 90
patients who died during the study to look for certain
physical signs associated with Alzheimer's disease such
as deposits of protein outside and around nerve cells.
The team found that the risk of developing
Alzheimer's disease increased by 51% for each point of
the loneliness score.
Those with the highest loneliness score
of 3.2 had about 2.1 times the risk of developing Alzheimer's
disease compared to those with a low score of 1.4.
When the researchers factored in social
isolation, such as if people had a small social network,
the results did not change significantly.
However there was no association between
loneliness and the brain pathology associated with Alzheimer's
Professor Wilson, professor of neuropsychology
at Rush University Medical Centre said: "There are two
ideas that we should take away, number one is it suggests
that loneliness really is a risk factor and secondly in
trying to understand that association we need to look
outside the typical neuropathology."
He said the results ruled out the possibility
that loneliness is a reaction to dementia.
It may be that loneliness may affect
systems in the brain dealing with cognition and memory,
making lonely people more vulnerable to effects of age-related
decline in neural pathways, he suggested.
"We need to be aware that loneliness
doesn't just have an emotional impact but a physical impact,"
Rebecca Wood chief executive of the Alzheimer's
Research Trust said: "This is an impressive study. It
follows a large group of people for a significant period
of time and comes up with startling findings that back
up earlier studies examining social interaction and Alzheimer's
"What I find particularly interesting
about this study is the fact that it is an individual's
perception of being lonely rather than their actual degree
of social isolation that seems to correlate most closely
with their Alzheimer's risk."
Dr Susan Sorensen, head of research at
the Alzheimer's Society agreed: "The study demonstrates
a clear link between less social activity and a higher
risk of dementia symptoms.
"However, it is interesting that the
people who died during the study and had demonstrated
symptoms of dementia did not have relatively more physical
signs of Alzheimer's disease in the brain.
"More research is needed to understand
the exact link between loneliness and dementia symptoms."