A recent population-based study conducted by researchers at Columbia University in New York found that patients who had been diagnosed with diabetes for a period of ten years or more were over three times more likely to suffer ischemic stroke. The study, called the Northern Manhattan Study, was a large, longitudinal investigation that allowed researchers to study how risk changed over long periods of time.
Scientists have known for years that patients with diabetes are at an increased risk of ischemic stroke. However, according to Dr. Julio R. Vieira, who presented the findings at the meeting of the American Neurological Association, the ten-year length of the study allowed researchers to look at long-term risks.
The study followed 3,298 participants of varied ethnic backgrounds. The participants had no prior history of stroke. They were tested for diabetes at baseline — the beginning of the study — and then tested again every year, starting in 1993.
The mean age of the participants at the beginning of the study was 69 years, with the ages ranging from 59 to 79. Over half of the participants were Hispanic, while 24 percent were black and 21 percent were white.
At the start of the investigation, 717 patients — 22 percent — had diabetes. An additional 338 patients (10 percent) developed diabetes throughout the course of the study.
Median follow-up among the participants was nine years. Throughout the follow-up period, 244 participants were diagnosed with ischemic stroke.
Researchers used Cox proportional hazards models to determine that the participants who had diabetes at the outset of the study were 2.5 times more likely to experience ischemic stroke throughout the course of the study. Additionally, the risk of suffering an ischemic stroke increased throughout the ten-year follow up period for patients who had diabetes at baseline as well as those were diagnosed with the disease during the study. Participants who had diabetes for five years or less increased their risk of ischemic stroke to 70 percent; those who had diabetes for five to ten years had an 80 percent risk of stroke; and patients who had diabetes for ten years or more were 3.3 times more likely to have an ischemic stroke.
Dr. Vieira stated in an interview conducted after his presentation that most of the participants involved with the study had been diagnosed with Type 2 diabetes. He noted that although diabetics were at an increased risk of ischemic stroke even from the beginning of the study, that risk did not triple until the patients had diabetes for ten years. Risk of stroke was always higher in diabetics but it took a fairly long history of the disease before the risk was significantly elevated.
“Diabetes, like hypertension and all of the other risk factors for cardiovascular disease, takes a while to really cause big damage,” said Dr. Vieira. “That’s exactly what we’re seeing here.” He stressed that patients who had been newly diagnosed with diabetes still had time to make changes to reduce their risk of stroke. “You have a lot of time for intervention,” he said.
However, the risk of stroke may be what compels diabetics to begin managing the disease more effectively. Dr. Vieira commented that even though he warns diabetics of the complications that can occur as a result of the disease, including vision loss and limb amputation, it doesn’t always incur changes. Significantly increased risk of a disabling or fatal stroke, however, may be the catalyst that drives diabetics to better manage the disease.