TUESDAY, Nov. 2 (HealthDay News) -- One of the main components
of fish oil doesn't help slow the development of symptoms in
patients with early Alzheimer's, although experts aren't ruling out
the possibility that supplementation given earlier might help
prevent the disease.
The supplement, docosahexaenoic acid (DHA), is present in
abundance in the brain and previous studies had suggested it might
play a role in treatment.
But that turned out not to be the case in this latest study,
which was funded by the U.S. National Institute on Aging and
appears in the Nov. 3 issue of the
Journal of the American Medical Association.
"Unfortunately, we have a very solid, but very negative, result that DHA supplementation did not slow the progression of Alzheimer's disease," study author Dr. Joseph Quinn said during a Tuesday news conference. "It's not going to help once a patient has already reached the point where they're able to be diagnosed with Alzheimer's disease. Maybe the study just started the treatment too late."
Quinn, who is assistant professor of neurology at Oregon Health
and Science University in Portland, could not say at what age DHA
supplementation might provide a benefit. Prevention trials have not
been done yet.
Duffy MacKay, vice president of scientific and regulatory
affairs at the Council for Responsible Nutrition, a group
representing the supplements industry, pointed out that the length
of the study was short (18 months), that participants were taking
small amounts of DHA and that they weren't taking another important
component of fish oil, eicosapentaenoic acid (EPA).
EPA is virtually absent in the brain, Quinn explained.
So the new study, "would suggest that intervening in a drug-like
way does not work," MacKay said. "What they really need to look at
is whether fish consumption or supplementation with omega-3 oils
throughout adulthood reduces the risk for developing Alzheimer's,"
For this study, about 400 men and women, average age 76, were
randomized to receive 2 grams daily of DHA or a placebo. All had
mild to moderate Alzheimer's, meaning "they had enough of an
impairment to justify a diagnosis but are living at home,
interacting with families and enjoying a pretty good quality of
life," Quinn said. "These are people for whom slowing the rate of
progression would really make a difference."
Participants weren't eating a lot of fish or taking supplements
at the start of the study.
Although both blood and cerebrospinal fluid levels of DHA
increased in the treatment group, there were no differences on two
different measures of cognitive function between the groups, Quinn
The only slightly encouraging news was that people without the
APOE-4 gene variant, which confers a higher risk of Alzheimer's,
may have benefited slightly. However, Quinn urged extreme caution
in interpreting this secondary analysis.
"It's not so solid a finding that it should change any treatment recommendations or advice to the public," he said.
A second study appearing in the same journal and presented at
the news conference found that being hospitalized or having
activity restricted as the result of illness or injury, as well as
general physical frailty, speeded an elderly person becoming
disabled or more disabled and even dying.
Not surprisingly, falls were at particular fault.
Only 117 participants were still nondisabled and alive at the
end of the study, which involved almost 800 elderly adults and
lasted a decade. An illness or injury leading to hospitalization
increased the likelihood of shifting from not disabled to severely
disabled more than 160-fold, said study author Dr. Thomas Gill, a
professor of medicine at Yale School of Medicine in New Haven,
Conn., where the research was conducted.
The Alzheimer's Association has ways to
maintain your brain.