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or reasons as yet unknown,
Alzheimer's disease is more likely to affect women. However, new research sheds
light on the potential impact of stress on their cognitive functioning.
Stress during midlife can put older women at risk of Alzheimer's disease.
Alzheimer's disease is
the most common type of dementia.
Affecting millions of
people in the United States, this progressive condition has no proven cause,
treatment, or cure.
What
researchers do know, however, is that women bear the brunt of the condition.
Almost two-thirds of U.S. individuals with Alzheimer's are
women, according to the Alzheimer's Association.
However,
only theories exist to explain this difference; there is no concrete evidence.
One
understudied area — say researchers at the Johns Hopkins University School of
Medicine in Baltimore, MD — is the role of stress on cognitive
function.
Previous
research has shown that age can have a significant impact on
women's stress response, and that a stressful life experience can cause memory
and cognitive issues. However, these problems tend to be short term.
Researchers
have now decided to look at the relationship between stress and the long term
cognitive decline associated with Alzheimer's.
"A
normal stress response causes a temporary increase in stress hormones like
cortisol and, when it's over, levels return to baseline and you recover,"
says Cynthia Munro, Ph.D., associate professor of psychiatry and behavioral
sciences.
"But
with repeated stress, or with enhanced sensitivity to stress, your body mounts
an increased and sustained hormone response that takes longer to recover
[from]. We know if stress hormone levels increase and remain high, this isn't
good for the brain's hippocampus — the seat of memory."
The importance of midlife
Data
from more than 900 Baltimore residents have revealed a link that could be key
in proving why women aged 65 and above have a 1 in 6 chance of developing Alzheimer's. The team's
findings now appear in the International
Journal of Geriatric Psychiatry.
The
residents had participated in the National
Institute of Mental Health's Epidemiologic Catchment Area study.
Participants first joined the study in the early 1980s.
Following
enrollment, they took part in interviews and checkups on three separate
occasions: once in 1982, once during 1993–1996, and once during 2003–2004. The
average age of the participants during the 1990s was 47, and 63% were women.
During
their third interview of four, the researchers asked each participant if they
had experienced a traumatic event in the past year. Such events included rape,
physical attacks, threats, natural disasters, or watching another person
sustain an injury or lose their life.
A
second question asked if they had had a stressful life experience in the same
time period, such as divorce, the death of a friend or family member, severe
illness, marriage, or retirement.
The
number of men and women reporting a traumatic experience was similar (22% of
men and 23% of women). The same went for stressful life events, with 47% of men
and 50% of women saying that they had experienced at least one during the
previous year.
At
their third and fourth appointments, the participants all took a standardized
memory test. One notable activity involved having to remember 20 words that
testers spoke aloud and repeating them straight away, as well as again 20
minutes later.
After analyzing their answers, the researchers
determined a women-only relationship between stressful life events during
midlife and a greater deterioration in remembering and recognizing words.
Women
who'd had at least one stressful life experience remembered one fewer word at
the fourth visit than the third, while women in the same category recognized
1.7 fewer words at their fourth interview.
On
average, women who reported no life stressors remembered 0.5 fewer words and
recognized 1.2 fewer words.
Altering the stress response
Traumatic
life events did not result in the same decline. According to Munro, this is
because chronic stress may have a greater impact on brain functioning than a
short term traumatic incident.
Notably,
there was no link between midlife stressful or traumatic experiences and memory
decline in men. Stressful experiences that occurred earlier in life also had no
impact on men or women.
Stopping
stress is an almost impossible task, but it may be possible to change the way
the body reacts to it. Munro explains that medications that could change how
the brain copes with stressful events are in the development stage.
Combining these with well-known stress relieving
techniques may help as people, particularly women, age.
These
findings are similar to those of a 2013 Swedish study in the journal BMJ Open.
That
team found a link between an increased number of midlife psychosocial stressors
— such as divorce, problems with children, and mental illness in a close
relative — and an increased risk of Alzheimer's disease.
Further
studies will need to examine if there is a cause and effect relationship
between stress and cognitive decline. If this is the case, altering the body's
stress response may be even more imperative.
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