Tight Glucose Control In Diabetes
Lowers Risk Of Atherosclerosis
Strict glucose control in type 1 diabetes reduces
the risk of atherosclerosis, a benefit that persists
for years.
Since 1993, when the Diabetes Control and Complications
Trial (DCCT) ended, researchers have known that
intensive glucose control greatly reduces the
eye, nerve, and kidney damage of type 1 diabetes.
Now, researchers conclude, the benefits of tight
control also extend to the heart.
"Intensive control is difficult to achieve
and maintain, but its benefits are even greater
than we realized," says study chair Dr. Saul
Genuth of the Case Western University. "The
earlier intensive therapy begins and the longer
it can be maintained, the better the chances of
reducing the debilitating complications of diabetes."
The DCCT was a multicenter study that compared
intensive versus conventional management of blood
glucose in 1,441 people with type 1 diabetes.
Patients on intensive treatment kept glucose levels
as close to normal as possible with at least three
insulin injections a day or an insulin pump and
frequent self-monitoring of blood glucose. Intensive
treatment aimed to keep hemoglobin A1c (HbA1c),
which reflects average blood sugar over 2 to 3
months, to as close to normal (6 percent) as possible.
Conventional treatment at that time consisted
of one or two insulin injections a day with daily
urine or blood glucose testing.
After 6½ years of the DCCT, HbA1c levels
averaged 7 percent in the intensively treated
group and 9 percent in the conventionally treated
group. When the DCCT ended, those who had been
assigned to conventional treatment were encouraged
to adopt intensive control and shown how to do
it, and researchers began a long-term follow-up
study of the participants, called the Epidemiology
of Diabetes Interventions and Complications (EDIC)
study.
The DCCT could not study atherosclerosis because
the participants were relatively young, and heart
disease takes years to develop. In 1994-95 and
again in 1998-2000, EDIC researchers used ultrasound
to measure the thickness of participants' carotid
arteries, the two blood vessels in the neck that
carry blood from the heart to the brain. Carotid
wall thickness reflects the amount of atherosclerosis,
or plaque build-up, in the artery: the thicker
the arterial wall the greater the risk of later
heart attack and stroke.
At the time of their first ultrasound, the diabetic
participants' carotid wall thickness was similar
to that of non-diabetic controls matched for age
and gender. Five years later, however, the participants
had thicker arterial walls than those of the non-diabetic
group. In addition, the thickness of the carotid
walls had increased less in the intensively treated
group during the 5 years than in the conventionally
treated group. "This finding strongly suggests
that atherosclerosis progressed more slowly in
the intensively treated group," noted Dr.
Genuth.
Carotid thickening was also linked to known cardiovascular
risk factors including age, higher systolic blood
pressure, smoking, LDL:HDL cholesterol ratio,
and urinary albumin (a measure of kidney function).
After adjusting for these factors, the study found
that the differences in carotid wall thickness
between the two groups were due to the differences
in blood glucose levels during the DCCT.
"The risk of heart disease is about 10 times
higher in people with type 1 diabetes than in
people without diabetes, but it was unclear to
what extent blood glucose contributed to the development
of heart disease," said Dr. David Nathan
of Massachusetts General Hospital, who co- chaired
the DCCT/EDIC research group. "Now we know
that intensively controlled glucose significantly
reduces the atherosclerosis underlying heart disease
just as it reduces damage to the eyes, nerves,
and kidneys in people with type 1 diabetes. What's
striking is that the benefits of intensive control
persisted despite a gradual rise in the HbA1c
levels of the intensively treated group during
the 5 years after DCCT ended."
"For many people, diabetes is difficult
to manage with today's tools. Every new finding
about the importance of blood glucose control
in preventing complications heightens our determination
to foster research that results in new therapies
that take the burden off the patient," said
Dr. Judith Fradkin, director of the Diabetes,
Endocrinology, and Metabolic Diseases Division
of the National Institute of Diabetes and Digestive
and Kidney Diseases (NIDDK). June 5, 2003 issue
of the New England Journal of Medicine. National
Institute of Diabetes and Digestive and Kidney
Diseases (NIDDK)
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