MONDAY, Oct. 11, 2010 (HealthDay News) -- People with insulin resistance may be at higher risk for stroke even if they don't have full-blown diabetes, a new study indicates.
Paying close attention to people who show signs of insulin resistance -- a reduction in the ability of the hormone insulin to clear glucose from the bloodstream -- may be helpful in preventing stroke, the researchers noted. Treating it may also reduce the risk of having an ischemic stroke, which occurs when blood supply to the brain is blocked.
"We showed that the increased risk of stroke among people with insulin resistance is three times higher than among those that don't have insulin resistance and are non-diabetic," said Dr. Tatjana Rundek, lead author of the study in the October issue of the Archives of Neurology. "That's telling us that there is a group of people that may be targeted for more treatment intervention in order to reduce the traditional vascular risk, but we cannot really say at this point that there are clinical implications."
Other experts agreed that widespread testing for insulin resistance is not ready for clinical use.
"This provides some additional evidence that insulin resistance may be an important risk factor, but I don't know how much more this study will impact . . . the type of screening that already happens in a doctor's office," said Dr. Adam Kelly, an assistant professor of neurology at the University of Rochester Medical Center in Rochester, N.Y. "Most physicians will probably wait for more evidence."
There are also problems with current methods to measure insulin resistance. According to an accompanying editorial, the best way to measure insulin resistance, the euglycemic hyperinsulinemic clamp, is "cumbersome."
The homeostasis model assessment (HOMA) index used in this study is easier to use, but doesn't measure insulin resistance directly. "It's a ratio between fasting glucose and fasting insulin levels," said Rundek, an associate professor of neurology at the University of Miami Miller School of Medicine. "It's not ideal, but it's a reasonable measure."
There's also no one accepted level for a diagnosis of insulin resistance. The condition is a known risk factor for heart disease but its effect on stroke hasn't yet been teased out.
These researchers followed 1,509 non-diabetic individuals (almost 60 percent Hispanic and 64 percent women) for close to nine years.
Individuals with the highest HOMA scores had an almost threefold increased risk of ischemic stroke, but not of heart attack, compared with lower-scoring participants, the researchers found.
People in the top group also had higher rates of obesity, were more sedentary and had higher blood pressure compared to the other participants, Kelly pointed out.
"These are patients we should probably already target as candidates for aggressive risk modification," he said.
Women with insulin resistance were at higher risk of having a first stroke than men (the reasons are unclear), but there were no racial or ethnic differences in the group studied, the authors noted.
It's also unclear if insulin resistance is actually causing stroke, or whether it's just another indicator of increased risk.
For now, Kelly said, "if you have patients who are having vascular events that don't appear to have any of these traditional vascular risk factors, it might be reasonable to check the HOMA score if that would make you treat their conventional risk factors or ask them to change their lifestyle more aggressively than you would have otherwise."
In the meantime, people can improve their insulin resistance with "diet and exercise and one or two medications," said Dr. Roger Bonomo, director of the stroke center at Lenox Hill Hospital in New York City.
More information
The American Stroke Association has more on ischemic stroke.
