People who live with type 1 diabetes for very
long duration show signs of mild decreases in cognitive abilities,
primarily in memory, compared to those who don't have the disease,
Joslin Diabetes Center researchers have shown.
The study compared Joslin 50-year Medalists, who have lived
successfully with type 1 diabetes for at least that long, with other
people of similar age with type 2 diabetes or without diabetes, says
Gail Musen, PhD, an assistant investigator in Joslin's Research
Division. The work is the first to evaluate whether cognitive function
is changing in an aging group of people who have successfully managed
their type 1 diabetes, a very complex disease associated with many
complications, for from 50 to more than 80 years.
The mild cognitive declines don't appear in clinical signs for these
Medalists, who remain in the normal range of function for people their
age, emphasizes Musen, who is lead author on the paper about the work
published in Diabetes Care.
Joslin investigators also examined how various measures of cognitive
health among these Medalists might correspond to common diabetes
complications. Most strikingly, "the memory changes are associated with
cardiovascular disease," says Hillary Keenan, PhD, a former principal
investigator on the Medalist study and corresponding author on the
paper.
The scientists tested and compared cognition in 82 Medalists, 31
age-matched individuals with type 2 diabetes and 30 age-matched
non-diabetic controls. Their investigation included standard tests for
memory, psychomotor speed and executive function (higher cognitive
processes involved in decision-making).
The memory tests required participants to recall a list of words
immediately after presentation as well as after a 30-minute delay.
Performance was significantly but not dramatically lower in people with
either form of diabetes than in people lacking the disease. While this
has been known for people with type 2 diabetes, the changes in memory in
aging people with type 1 diabetes had not been clearly established.
In the psychomotor test, the researchers looked at how quickly and
well subjects inserted small key-shaped pegs into similarly shaped slots
that have been rotated to require fine motor dexterity. Medalists on
average performed slightly worse than those without diabetes. This
diminished performance was associated with proliferative diabetic
retinopathy, an advanced form of eye disease. (However, it didn't
reflect poorer vision, since Medalists wore their corrective lenses.)
The executive-function test scored how quickly and accurately
participants put scrambled letters and numbers into a given order. Here
the Joslin team also saw a tendency of slightly worse results among
Medalists than their peers without diabetes.
"Overall, nobody among the Medalists needs to worry; this is a very
healthy group that's showing minimal signs of cognitive decline," Musen
stresses. "However, these small deficits may be avoidable with self-care
behaviors that help minimize diabetes complications."
Previous research on the Medalists has consistently found that
moderate physical exercise is linked to a reduction in cardiovascular
disease. The latest findings provide yet another incentive for people
with type 1 diabetes to pursue physical exercise, in addition to
following general guidelines for healthcare and diabetes management,
says Keenan.
With the incidence of type 1 diabetes on the rise, Joslin continues
to examine the long-term effects of the disease on cognition and other
complications, says George King, MD, Joslin's Chief Scientific Officer
and Director of Research Division. "We want to further study this
population, to better understand these processes and find therapies to
protect against them," he says. "Since both eye and cardiovascular
diseases in diabetic patients are treatable, we are very hopeful the
cognitive decline in type 1 diabetes is also preventable."
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