Alzheimer's, Dementia & Mental Health
Dementia risk climbs in seniors as blood sugar level
increases, even without diabetes
Diabetes has been linked dementia risk but this study
finds it also increases in senior citizens without this disease
Aug. 8, 2013 – In testing of senior citizens,
researchers have concluded there is a link between higher blood sugar
levels and a higher risk of developing dementia, even among people who
do not have diabetes. And, incrementally higher glucose level was
associated with a higher risk of dementia in those without diabetes. An
association between dementia and diabetes had been found in previous
In this study, for example, in people without
diabetes, risk for dementia was 18 percent higher for people with an
average glucose level of 115 milligrams per deciliter compared to those
with an average glucose level of 100 mg/dl.
And, in people with diabetes, whose blood sugar
levels are generally higher, dementia risk was 40 percent higher for
people with an average glucose level of 190 mg/dl compared to those with
an average glucose level of 160 mg/dl.
Blood sugar levels averaged over a five-year period
were associated with rising risks for developing dementia.
The study involved 2,067 randomly sampled men and
women age 65 and older who underwent numerous glucose tests as part of
their biennial work-ups, beginning in the 1990s. They were patients in
the Adult Changes in Thought (ACT)
study. This study published in the New England Journal of Medicine
was a joint project of Group Health and the University of Washington.
“The most interesting finding was that every
incrementally higher glucose level was associated with a higher risk of
dementia in people who did not have diabetes,” said first author
Paul K. Crane, MD, MPH,
an associate professor of medicine at the UW School of Medicine, adjunct
associate professor of health services at the
UW School of Public Health,
and affiliate investigator at Group Health Research Institute.
“There was no threshold value for lower glucose
values where risk leveled off.”
“One major strength of this research is that it is
based on the ACT study, a longitudinal cohort study, where we follow
people for many years as they lead their lives,” said senior author
Eric B. Larson, MD, MPH,
a senior investigator at Group Health Research Institute who also has
appointments at the UW Schools of Medicine and Public Health.
“We combine information from people’s research
visits every other year with data from their visits to Group Health
providers whenever they receive care. And this gave us an average of 17
blood sugar measurements per person: very rich data.”
These measurements included blood glucose (some
fasting, some not) and glycated hemoglobin (also known as HbA1c). Blood
sugar levels rise and fall in peaks and valleys throughout each day, but
glycated hemoglobin doesn’t vary as much over short intervals.
Combining glucose and glycated hemoglobin measures
into a composite measure required special statistical techniques, which
Drs. Crane and Larson’s co-authors
Rod Walker, MS, a
Rebecca Hubbard, PhD, an
associate investigator, both from Group Health Research Institute, had
developed. (Dr. Hubbard is also an affiliate assistant professor of
biostatistics at the UW School of Public Health.)
These sophisticated statistical models required
specialized data on the relationships between glycated hemoglobin and
glucose levels, and they used data generated by co-author
David M. Nathan, MD, a
professor of medicine at Harvard Medical School and director of the
Diabetes Center at Massachusetts General Hospital.
What preventive measures should be considered
So should people try to eat less sugar - or foods
with a lower “glycemic index”? Not necessarily.
“Your body turns your food into glucose, so your
blood sugar levels depend not only on what you eat but also on your
individual metabolism: how your body handles your food,” according to
But he does suggest that taking walks couldn’t
hurt: The ACT study has previously linked
physical activity to
later onset and reduced risk of dementia, including Alzheimer’s disease.
Furthermore, Dr. Crane emphasized that these
results come from an observational study: “What we found was that people
with higher levels of glucose had a higher risk of dementia, on average,
than did people with lower levels of glucose,” he said.
“While that is interesting and important, we have
no data to suggest that people who make changes to lower their glucose
improve their dementia risk. Those data would have to come from future
studies with different study designs.”
More research is planned to delve into various
possible mechanisms for the relationship between blood sugar and
dementia. “This work is increasingly relevant,” Dr. Crane said, “because
of the worldwide epidemics of dementia, obesity, and diabetes.”
Dallas Anderson, a scientist at the National
Institute on Aging, the agency that paid for the study, told the
Associated Press that a "clean pattern" had emerged, showing the
risk of developing Alzheimer's rose as blood sugar did.
The study added evidence that exercising and
controlling blood pressure, blood sugar and cholesterol was a viable way
to delay or prevent dementia, Dr Anderson said.
Because so many attempts to develop effective drugs
had failed, managing blood sugar "looks like, at the moment, our best
bet", he told the AP.
The study was supported by grant U01 AG06781 to Dr.
Larson, principal investigator, from the National Institute on Aging of
the National Institutes of Health.
Additional co-authors included
Ge (Gail) Li, MD, PhD,
associate professor of psychiatry and behavioral sciences,
Thomas Montine, MD, PhD,
professor and chair of pathology,
Wayne McCormick, MD, MPH,
professor of medicine, all at the UW School of Medicine;
Susan McCurry, PhD,
research professor in the UW School of Nursing, adjunct research
professor of psychiatry and behavioral sciences at the UW School of
Medicine, and an affiliate investigator at Group Health Research
Steven Kahn, MB, ChB,
professor of medicine at the UW School of Medicine and VA Puget Sound
Healthcare System and director of the UW’s Diabetes Research Center;
Hui Zheng, PhD, assistant
professor at Harvard Medical School and Massachusetts General Hospital;
Sebastien Haneuse, PhD,
associate professor of biostatistics at Harvard School of Public Health;
Suzanne Craft, PhD,
professor of gerontology and geriatric medicine at Wake Forest School of
Medicine, in Winston-Salem, NC; and
James Bowen, MD, of
Swedish Neuroscience Institute in Seattle.
Adult Changes in Thought (ACT) study
Begun in 1994, the Adult Changes in Thought (ACT)
study is a collaboration between Group Health and the University of
Washington. This longitudinal study follows adults age 65 and older to
identify risk factors for cognitive decline with aging and related
conditions, such as Alzheimer's disease. Men and women with no cognitive
impairment are randomly selected and invited to participate. At the time
of enrollment, all are Group Health members.
Participants visit the Group Health Research Clinic
every two years for physical and cognitive assessments. By combining
these data with comprehensive medical and pharmacy records and
biospecimens collected at the baseline enrollment visits, investigators
have established a promising scientific resource for understanding
dementia, including Alzheimer's disease. The study continues to follow
people still alive from the original enrollment and replaces those who
die with new volunteers, keeping study enrollment at about 2,000 people.
The ACT study and its predecessor, the UW–Group
Health Alzheimer's Disease Patient Registry, have had continuous
National Institutes of Health (NIH) funding for 27 years. Like the
celebrated Framingham Heart Study, ACT is a longitudinal cohort study of
people leading their lives in a community. That means it follows a large
group of people at regular intervals over a long time to see what
happens to them. A distinguishing feature of ACT is that, because its
participants are selected from patients in the Group Health
care-delivery system, the study has access to extensive information
collected during visits to providers that happen separate from the
UW Medicine health system
includes Harborview Medical Center, Northwest Hospital and Medical
Center, Valley Medical Center, UW Medical Center, UW Neighborhood
Clinics, UW Physicians, UW School of Medicine, and Airlift Northwest. UW
Medicine also shares in the ownership and governance of Children’s
University Medical Group and Seattle Cancer Care Alliance, a partnership
among UW Medicine, Fred Hutchinson Cancer Research Center, and Seattle
Children’s. UW Medicine has major academic and service affiliations with
Seattle Children’s, Fred Hutchinson Cancer Research Center, Veterans
Affairs Puget Sound Health Care System in Seattle, and the VA Hospital
in Boise, Idaho. The UW School of Medicine is the top public institution
for biomedical research in funding received from the National Institutes
Group Health Research Institute
Group Health Research Institute
does practical research that helps people stay healthy. The Institute is
the research arm of Seattle-based
Group Health Cooperative,
a consumer-governed, nonprofit health care system. Founded in 1947,
Group Health Cooperative coordinates health care and coverage. Group
Health Research Institute changed its name from Group Health Center for
Health Studies in 2009. Since 1983, the Institute has conducted
nonproprietary public-interest research on preventing, diagnosing, and
treating major health problems. Government and private research grants
provide its main funding.
Glucose levels and risk of dementia
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