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 The new report, using data from the long-running Framingham Heart
Study, shows that dementia rates have decreased by 44 percent since
the late 1970s and early 1980s, with nearly all of that drop among
high school graduates.
It was a collective reduction in all causes of senility that
produced the significant fall, researchers said. Dementia caused by
vascular diseases, such as stroke, accounted for the much of the
drop. Alzheimer's disease showed a reduction, but it wasn't
dramatic, and could be a statistical fluke, they said.
"There was a trend there" for Alzheimer's, said Dean Hartley,
director of science initiatives with the Alzheimer's Association. It
shows "there may be modifiable lifestyles that may lower your risk
for Alzheimer's."
So many people are entering the age when dementia becomes a threat
and life expectancy is increasing so rapidly, the decline in rates
of dementia will not translate to an overall drop in the number of
dementia cases, cautioned senior author Dr. Sudha Seshadri, a
professor of neurology at the Boston University School of Medicine.
"We don't know completely what's bringing down the rates," she told
Reuters Health. "The good news is, we are doing something right. The
bad news is we need to understand this much better if we want to
effectively continue the trend."
The Framingham study is based in a predominately-white Massachusetts
town west of Boston where thousands of residents have been closely
followed by doctors since 1948. The new analysis, reported in the
New England Journal of Medicine, looked at dementia rates in four
5-year blocks and used data from 5,205 individuals.
Dementia rates were 3.6 percent among people aged 60 years and older
beginning in 1977, falling to 2.8 percent for the block of people
who were over 60 beginning in 1986, then 2.2 percent for the block
starting in 1992 and 2.0 percent for the most recent block, from
2004 to 2008.
Those declines translate to reductions of 22 percent, 38 percent and
44 percent in the second, third and fourth period, respectively,
compared to the rate in the early years.
The researchers said some of the drop may be due to declines in
rates of stroke, heart failure and atrial fibrillation, as well as
better treatments for those conditions, "but none of these trends
completely explain the decrease in the incidence of dementia."
Residents without a high school diploma showed no decline in
dementia, perhaps because improvements in heart health were only
seen among people who had graduated from high school, the study team
notes.
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Dr. Paul Schulz, a dementia neurologist at the University of Texas
Health Science Center in Houston, who was not connected to the
research, pointed out that "there's a lot of healthcare access
issues related to education (and graduates) may have better
insurance to see their doctor more often," which might have affected
the results.
In addition, he said, "People who have more education may be blessed
with more brain power. They may have more ability to lose function
before they develop symptoms. In this study they're speculating that
getting more education might be valuable, but it might be a chicken
and egg question here."
Dementia also tended to show up later in life as time went on, the
study found. The average age of diagnosis was 80 during the late
1970s and 85 in the most recent group.
"Rising educational levels might have contributed to the 5-year
delay we observed in the mean age at onset of clinical dementia,"
the researchers said.
"One of the limitations of the Framingham Heart Study is that the
participants are overwhelmingly of European ancestry; therefore, our
findings would need to be replicated in groups that include a larger
number of participants of other races and ethnic backgrounds,” they
cautioned.
Hartley said it's important to fund more research to see what
lifestyle changes might lower the risk further. "A number of things
people to do to stay healthy" such as exercise, a better diet and
social stimulation "could protect their brain," he said
SOURCE: http://bit.ly/1RcPhxT New England Journal of Medicine,
online February 10, 2016.
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