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Risk lowered for heart disease,
stroke with glucose control
Intensive glucose control lowers the risk of heart disease and stroke
by about 50 percent in people with type 1 diabetes, researchers
reported in the Dec. 22, 2005, issue of the “New England Journal of
Medicine.” Their findings were 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. MUSC was one of 28 centers across the
country that participated in the DCCT.
The DCCT results, first 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.
“Heart disease is about 10 times more common in people with type 1
diabetes than in people who don’t have diabetes,” said John Colwell,
M.D., Ph.D., who led MUSC’s participation in the DCCT and the follow-up
study of DCCT participants. “Now we know that intensive glucose
control also protects the heart and blood vessels. Maintaining
tight control is challenging, but 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 during
the past two to three 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 during the next decade,
they observed another advantage of intensive control: its long-lasting
effects. The benefits of the first six years of intensive control
persisted even though the average blood glucose level of the
intensively treated group gradually rose to an HbA1c value of about 8
percent—the same level of the conventionally treated group, which
declined. In the new reported results
in December, 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.
Friday, Jan. 6, 2006
Catalyst Online is published weekly,
updated
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