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 This, at least, is how things unfolded after the 2011 tsunami and
earthquake in Japan, according to the study of 3,556 elderly
survivors of this disaster.
"In the aftermath of disasters, most people focus on mental health
issues like post traumatic stress disorder," said lead study author
Hiroyuki Hikichi, a public health researcher at Harvard University
in Boston. "But our study suggests that cognitive decline is also an
important issue.”
While previous research has documented cognitive decline and
dementia among the elderly after disasters including Hurricanes
Katrina and Rita in the U.S., the current study of survivors from
the 2011 earthquake and tsunami in Japan offers a unique snapshot of
the factors that may influence the odds that these problems will
emerge, Hikichi said by email.
That’s because in the current study, researchers had survey data
documenting risk factors and rates of dementia both before and after
the disaster.
Researchers examined survey data from a group of elderly residents
of the coastal city of Iwanuma. The earthquake’s epicenter was in
the ocean about 80 kilometers (50 miles) due east of Iwanuma, where
nearly half the land area was inundated by the subsequent tsunami.
Seven months before the disaster, elderly residents of Iwanuma had
been surveyed about their health as part of an ongoing study of
aging called the Japan Gerontological Evaluation Study (JAGES).
Two-and-a-half years after the tsunami, the researchers conducted a
follow-up survey among members of the same group.
Overall, 38 percent of the participants said they lost relatives and
friends and about 59 percent reported property damage after the
disaster, researchers report in Proceedings of the National Academy
of Sciences, October 24th.
Before the tsunami, about 4 percent of these older adults had at
least some symptoms of dementia, the study found. Two and a half
years later, about 12 percent of them had some dementia symptoms.
Stroke became more common too. About 3 percent reported a previous
stroke before the disaster, compared to almost 7 percent afterwards.
At the same time, the proportion of people who reported no contact
with neighbors – not even greetings on the street – almost doubled
from 1.5 percent to 2.9 percent.
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People who wound up in temporary housing after their houses were
either destroyed or sustained major damage had the highest levels of
cognitive decline. The decline was also steeper for people with the
most damaged homes, compared to people with homes that had only mild
damage.
Depression and declines in informal social interactions with friends
and neighbors appeared to influence the odds of dementia or
cognitive decline after the disaster, but the loss of family and
friends didn’t seem to be a factor.
“It appears that relocation to a temporary shelter after a disaster
may have the unintended effect of separating people not just from
their homes but from their neighbors - and both may speed up
cognitive decline among vulnerable people,” Hikichi said.
The study doesn’t prove that housing damage causes dementia. One
limitation of the analysis is that researchers can’t rule out the
possibility that people at risk for dementia and cognitive decline
were also more likely to be living in homes with greater potential
for damage, the authors note.
Still, the link between stress and dementia is well known and it’s
quite plausible that housing damage and displacement after a
disaster would be a significant source of stress, said Dr. Richard
Lipton, an aging and neurology researcher at Albert Einstein College
of Medicine and Montefiore Medical Center in New York.
Stress from displacement could lead to surges in cortisol, a stress
hormone, and activation of what’s known as the sympathetic nervous
system, a fight or flight response, potentially increasing memory
decline and the risk of dementia, Lipton, who wasn’t involved in the
study, said by email.
“Under this hypothesis we would predict that stress management,
meditation, social support and other interventions might reduce the
impact of catastrophic events on brain function,” Lipton added.
SOURCE: http://bit.ly/2f896Ma
Proc Natl Acad Sci 2016.
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