NEW YORK (Reuters Health) - Among older
adults with dementia, those who are also depressed tend to have more
rapid cognitive decline, according to a new study.
“Many studies have found that older people with some depression are
more likely to develop cognitive decline or dementia,” Robert S.
Wilson said.
But there has been disagreement over whether depression actually
contributes to cognitive decline or whether both are the result of
other underlying problems, he told Reuters Health.
Wilson worked on the study at the Rush Alzheimer’s Disease Center in
Chicago.
He and his coauthors analyzed data on 1,700 people over age 50 who
initially had no cognitive problems and were followed for an average
of eight years. Each year doctors evaluated participants’ depression
symptoms and tested their thinking and memory skills.
About half of the original group developed mild cognitive
impairment, which often comes before dementia, and 18 percent were
diagnosed with dementia.
Participants who had more depression symptoms on their initial exams
were more likely to experience cognitive decline.
Depression symptoms were also linked to dementia and to more rapid
decline after a dementia diagnosis, according to results published
in Neurology.
Almost 600 of the participants died during the study and their
brains were examined postmortem.
Among those participants, depression was still associated with
faster mental decline when amyloid plaques - considered the
hallmarks of Alzheimer’s disease - and other neuropathological
problems found on autopsy were taken into account.
“Late life dementia is a very complex disorder and there are many
factors that contribute to it, and depression is one of those
factors,” Wilson said.
Depression accounted for five percent of the variability in mental
decline that couldn’t be attributed to other problems with the
brain, he said.
Depression symptoms did not increase once cognitive decline started,
and actually decreased once dementia was diagnosed. Depression
itself is an organized process of the brain, and as brain function
declines it is common for people to experience periods of
unhappiness but it is rare that those periods are consistent, Wilson
said.
Dr. Amos D. Korczyn, professor emeritus of neurology at Tel Aviv
University in Israel, called the study an “important contribution”
to scientists’ understanding of how cognitive decline, depression
and changes in the brain may be linked.
“Obviously as the authors note, more work needs to be done to better
understand the relationship of depression to dementia which is so
important when trying to modify the disease course,” he told Reuters
Health in an email.
Depression symptoms are common among people with dementia,
especially early on in the disease, he said.
It’s still unclear exactly how depression might lead to cognitive
decline and dementia, Wilson said.
“Depression is probably doing something to your brain if it’s
affecting cognition,” Wilson said. “We think in the meantime there
ought to be thought given to the importance of treating depression
for these people.”
Treating depression with medication or behavioral therapy might
enhance mental function among people with cognitive decline or
dementia, he said.
There isn’t much scientific evidence that antidepressants are
effective for people with dementia but most doctors prescribe them
and the impression is that they provide some relief, Korczyn said.
“People with depression, as well as those who are demented,
frequently tend to avoid exposure to others, even to friends and
this may exacerbate the depression,” Korczyn added. “They should be
encouraged to be socially integrated.”
Caregivers often become depressed as well, and as they are usually
spouses, are neither young nor necessarily healthy themselves, he
noted. They should be offered help and moral support as well.
