Insulin Resistance a Double Whammy for Persons with
Blood sugar control might have little influence over the
development of heart disease in type 1 diabetics, a new study
Instead, researchers say insulin resistance -- the hallmark of
type 2 diabetes -- is a better indicator of who's going to get
heart disease among type 1 diabetics.
"We suspect that insulin resistance occurs in those with type 1
diabetes in the same way as it does those with type 2,
essentially giving these individuals 'double diabetes' and
greatly increasing their risk of heart disease," says Dr. Trevor
Orchard, acting chairman of the department of epidemiology at
the University of Pittsburgh Graduate School of Public Health.
The study appears in the May 2003 issue of the Diabetes Care
For type 1 diabetics, this may come as good news. It might mean
that some type 1 diabetics, at least those without insulin
resistance, are at lower risk of heart disease than previously
believed, Orchard says.
And while those with insulin resistance may be at higher risk,
medications and lifestyle changes can boost the body's ability
to use insulin.
Type 1 and type 2 diabetes are, in many ways, very different
diseases, Orchard says.
Type 1, most often thought of as a disease that strikes in
childhood, occurs when the body attacks and destroys its own
insulin-producing beta cells. Insulin is responsible for helping
tissues use glucose, the body's energy source.
Type 1 diabetes, the less common form of the illness, accounts
for 5 percent to 10 percent of the 17 million people in the
United States with diabetes, according to the American Diabetes
Association. Type 1 diabetics need daily insulin injections to
In Type 2 diabetes, the pancreas is usually still producing
insulin, but the cells of the liver, muscles and fatty tissues
develop a resistance to it. Type 2 can often be controlled with
weight loss, diet and exercise.
Doctors have known for a long time that people with diabetes are
at higher risk of heart disease, but most of the research has
been done in type 2 diabetics, says Dr. Nathaniel Clark,
national vice president of clinical affairs for the American
"The question keeps coming up: 'What about type 1 diabetics?'"
Clark says. "There have been very few studies that have shown
the risk factors for people with type 1."
When trying to help diabetics control their risk of heart
disease, doctors tend to focus on three risk factors: blood
sugar, blood pressure and cholesterol. But it's unknown which is
the most significant factor, or if, perhaps, one factor matters
more or less in type 1 or 2 diabetes, Clark says.
Orchard's study begins to get at that, he says.
"I think the most important finding is that these researchers
looked at the traditional risk factors, and what they found was
that blood sugar wasn't terribly helpful in predicting who gets
heart disease," Clark says. "There were other factors that were
much more important."
Namely, insulin resistance.
Orchard and his colleagues examined 658 type 1 diabetics, aged 6
to 40, every two years for a 10-year-period. During that time,
there were 108 cardiovascular events, including angina and heart
Researchers then took a subset of 24 patients and measured their
insulin resistance using a type of testing that's considered the
gold standard. The problem with this test is that it's
time-consuming -- patients have to stay overnight in the
hospital -- and expensive.
So Orchard and his colleagues developed a surrogate test for
insulin resistance using data about the patients' waist-to-hip
ratio, blood pressure and long-term blood sugar levels.
They found that type 1 diabetics with the highest levels of
insulin resistance based on these calculations were the most
likely to have a cardiovascular event.
Dr. Loren Wissner Greene, an endocrinologist at New York
University Medical Center, is skeptical of the need for
complicated calculations. In treating type 1 diabetics, she says
she occasionally sees people who gain a lot of weight and become
One easy way of telling if the patients are becoming
insulin-resistant is if, over time, they require more and more
insulin to maintain their blood sugar.