Not every moment of forgetfulness is a sign of Alzheimer's
disease. Everyone has occasional memory lapses. However, there
are factors that may increase your risk of developing the
disease.
Alzheimer's disease affects brain tissue directly, causing
progressive brain deterioration in middle or late life. So far,
only age and heredity are proven risk factors. But like cancer
and cardiovascular disease, Alzheimer's probably results from
a combination of factors. Researchers are studying:
Age — Alzheimer's usually affects
people older than age 65, but can, rarely, affect those younger
than age 40. The average age at diagnosis is about 80.
Only one to two people in 100 have Alzheimer's at age 65,
but that risk increases to about one in five by age 80. By age
90, half of all people have some symptoms.
The incidence of Alzheimer's is about the same for all
races, but women are more likely than men to develop the disease,
in part because they live longer.
Heredity — Family history plays a role in
about 40 percent of people with early onset Alzheimer's. If
your parents or a sibling developed Alzheimer's, you're
more likely to as well. But, even in families with several people
who've had Alzheimer's, most members don't get it.
It's clear that most Alzheimer's involves some disease
process in addition to a genetic vulnerability.
Environment — Researchers are studying
environmental factors to discover both possible causes and
preventions of Alzheimer's. For example, some people with
Alzheimer's have small deposits of aluminum in their brains.
But scientists who've studied environmental aluminum sources
from antacids and antiperspirants to cooking pots and drinking
water haven't found a link between aluminum and
Alzheimer's.
On the other hand, some studies hint at a possible protective
effect from estrogen, nonsteroidal anti-inflammatory drugs
(NSAIDs), vitamin E and other factors. But more research is
needed to confirm any benefit.
Can you reduce your risk?
Scientists are combing the environment for clues about ways to
delay or prevent Alzheimer's disease and to reduce risk of
the disease. They're following several hopeful, but very
preliminary, leads:
NSAIDs — A long-term study released in
June 1996 showed that the nonsteroidal anti-inflammatory drugs
(NSAIDs) ibuprofen (Advil, Motrin, Nuprin), naproxen sodium
(Aleve) and indomethacin (Indocin) reduced risk of
Alzheimer's by 30 percent to 60 percent. Doctors think brain
inflammation occurs as one stage in the development of
Alzheimer's. Investigators were uncertain why aspirin, which
is also an anti-inflammatory drug, and acetaminophen (Tylenol),
which is not, had no effect.
The study reinforced an earlier one that compared NSAID use in
twins. That study found that a twin who used NSAIDs regularly,
usually for arthritis, was 10 times less likely to develop
Alzheimer's than the twin who wasn't taking an NSAID.
But, doctors don't recommend taking NSAIDs, which can cause
gastrointestinal bleeding, solely to prevent Alzheimer's
until more research confirms these results.
Vitamin E and selegiline — An ongoing
study at several sites, including Mayo, is looking at vitamin E
and selegiline (Eldepryl), a drug used to treat Parkinson's
disease, for a possible protective effect against the progression
of Alzheimer's. These substances may slow the rate of decline
in people with moderately severe Alzheimer's.
Vitamin E and selegiline are antioxidants and may prevent nerve
cell damage by destroying toxic free radicals. Free radicals are
byproducts of normal cell metabolism. Some scientists think free
radicals are discharged by immune cells that are in the brain
responding to chronic brain inflammation from Alzheimer's.
The free radicals may attach to molecules in the nerve cell
membrane and disrupt function.
Estrogen — Alzheimer's disease in
older women may be related to estrogen deficiency. Estrogen may
interact with nerve growth factors and delay the degeneration of
neurotransmitters that facilitate memory and learning. Recent
studies show that estrogen replacement after menopause can reduce
a woman's risk of developing Alzheimer's by 30 percent to
40 percent. And evidence is growing that estrogen replacement
therapy can improve mental abilities, especially verbal memory,
in women who already have Alzheimer's. But because the impact
of estrogen is still not proven, you shouldn't begin
replacement therapy solely to prevent Alzheimer's.
Mental fitness — Another study shows that
maintaining mental fitness may delay onset of dementia. The study
focused on a large order of nuns reported to have significantly
lower rates of Alzheimer's, even though their average age is
85 and many are in their 90s. The study is intriguing because
most other environmental factors affecting the nuns, such as diet
and environment, are the same.
Many of the nuns have advanced academic degrees and lead an
intellectually challenging life into old age. Some researchers
believe that lifelong mental exercise and learning may promote
the growth of additional synapses, the connections between
neurons, and delay the onset of dementia. Other researchers argue
that advanced education gives a person more experience with the
types of memory and thinking tests used to measure dementia. This
advanced level of education simply may help some people
"cover" their condition until later.
