(Philadelphia, PA) - Intensive glucose control
lowers the risk of heart disease and stroke by about 50 percent
in people with type 1 diabetes, researchers report in the December
22, 2005, issue of the New England Journal of Medicine.
Their findings are based on a follow-up study of patients who took
part more than a decade ago in the Diabetes Control and Complications
Trial (DCCT), a major clinical study funded by the National Institutes
of Health. The Division of Endocrinology, Diabetes, and Metabolism
at the University of Pennsylvania School of Medicine,
with physicians from the Children’s Hospital of Philadelphia
(CHOP), was one of 28 centers across the country that participated
in the DCCT.
The DCCT results, announced in 1993, clearly showed that intensive
glucose control prevents or delays the eye, nerve, and kidney complications
of type 1 diabetes. At the time, however, researchers had not followed
participants long enough to know whether tight control also lowered
the risk of heart attack and stroke.
“Now we know that intensive glucose control with insulin also
protects the heart and blood vessels,” says Stanley
Schwartz, MD, Associate Professor of Medicine, who along
with Lester Baker, MD, (now deceased), from CHOP, led Penn’s
participation in the DCCT and the follow-up study of DCCT participants.
“Maintaining tight control is challenging, but easier than
ever with the newer insulins available and it confers huge benefits,
both in the short and long term. Intensive control should begin
as soon as possible and be maintained as long as possible.”
The DCCT compared intensive management of blood glucose to conventional
control in 1,441 people with type 1 diabetes. Patients 13 to 39
years of age took part in the trial between 1983 and 1989. At the
time, conventional treatment consisted of one or two insulin injections
a day with daily urine or blood glucose testing. Participants randomly
assigned to intensive treatment were asked to keep glucose levels
as close to normal as possible. That meant trying to keep hemoglobin
A1c (HbA1c) levels at 6 percent or less with at least three insulin
injections a day or an insulin pump, guided by frequent self-monitoring
of blood glucose. (HbA1c reflects average blood glucose over the
past 2 to 3 months.)
The DCCT findings--that intensive glucose control greatly lowers
the eye, nerve, and kidney damage of type 1 diabetes--prompted a
major shift in the way doctors manage their patients with type 1
diabetes. At the end of the study, HbA1c levels averaged 7 percent
in the intensively treated group and 9 percent in the conventionally
treated patients, who were then encouraged to adopt intensive control
and shown how to do it.
As researchers continued to follow participants over the next decade,
they observed another advantage of intensive control: its long-lasting
effects. The benefits of the first 6 years of intensive control
persisted even though the average blood glucose level of the intensively
treated group had gradually risen to a HbA1c value of about 8 percent-the
same level of the conventionally treated group, which had declined.
In the most recent results, tight glucose control lowered the risk
of a CVD event by 42 percent and the risk of a serious event, including
heart attack or stroke, by 58 percent. Among the 1,375 volunteers
continuing to participate in the study, the intensively treated
patients had less than half the number of CVD events than the conventionally
treated group (46 compared to 98 events). Such events included heart
attacks, stroke, angina, and coronary artery disease requiring angioplasty
or coronary bypass surgery. Thirty-one intensively treated patients
(4 percent) and 52 conventionally treated patients (7 percent) had
at least one CVD event during the average 17 years of follow-up
from the start of the DCCT. The average age of participants is now
45 years; 53 percent are male.
Is glucose control as important for people with type 2 diabetes?
Mounting evidence suggests that tight control benefits everyone
with diabetes, but strict control is hard to sustain and can lead
to episodes of hypoglycemia, or low blood glucose. Researchers expect
that a definitive answer will come from the ACCORD trial (Action
to Control Cardiovascular Risk in Diabetes), a major study testing
ways to lower the risk of heart disease and stroke in adults with
type 2 diabetes. Results of this NIH-funded study are due in 2009.
Nearly 21 million people in the United States-7 percent of the population-have
diabetes, the most common cause of blindness, kidney failure, and
amputations in adults and a major cause of heart disease and stroke.
At least 65 percent of people with diabetes will die from a heart
attack or stroke, yet two out of every three people with diabetes
are unaware of their increased risk.
Type 1 diabetes accounts for about 5 to 10 percent of all diagnosed
cases of diabetes in the U.S. This form of diabetes usually strikes
children and young adults, who need three or more insulin injections
a day or an insulin pump to maintain the level of blood glucose
control shown to prevent or delay long-term complications. Most
people with type 1 diabetes who were treated with conventional glucose
control, as it was defined before the DCCT, develop one or more
complications, including damage to the heart and blood vessels,
eyes, nerves, and kidneys. Today, such complications are much less
likely to occur if patients begin intensive treatment promptly after
the onset of diabetes.
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