02/02/12

SAN DIEGO – The risk of ischemic stroke more than triples in patients with a 10-year history of diabetes, according to results of the population-based Northern Manhattan Study.

Ischemic stroke has long been associated with diabetes but a large, longitudinal study enabled investigators to explore how risk changes over time, Dr. Julio R. Vieira said at the annual meeting of the American Neurological Association. Details of the Northern Manhattan Study are available at www.columbianomas.org/study.html.

Columbia University researchers fol- lowed 3,298 multiethnic patients who had no prior history of stroke, assessing for diabetes at baseline and annually, beginning in 1993.

At baseline, the mean age of subjects was 69 years (range, 59–79). More than half were Hispanic, with 24% black and 21% white.

Initially, 717 patients (22%) had diabetes and 338 (10%) developed new-onset diabetes over the course of the study.

During a median of 9 years of follow- up, 244 patients were diagnosed with ischemic stroke.

In Cox proportional hazards models, patients with diabetes at baseline faced a 2.5-fold increased risk of having an ischemic stroke during the study period. Among those patients and those who developed de novo diabetes, the risk of ischemic stroke rose over time. Risk was elevated 70% among patients with diabetes for 5 years or less, 80% for those with a 5- to 10-year history of diabetes, and 3.3-fold for those with at least a 10-year history of the disease.

The majority of patients in the study had type 2 diabetes, said Dr. Vieira during an interview.

Although risk of ischemic stroke was present from the start in diabetic patients, it did not triple for a decade, he stressed. “Diabetes, like hypertension and all of the other risk factors for cardiovascular disease, takes a while to really cause big damage,” he said. “That’s exactly what we’re seeing here.”

To Dr. Vieira, a research fellow at the Neurological Institute of New York at Columbia University, the message for physicians and patients alike is, “You have a lot of time for intervention.”

He said that in his own experience, warning diabetic patients of impending problems with their eyes, hearts, or extremities does not always seem to get their attention.

Perhaps it would be more sobering to tell them that they have 10 years to get the disease under control or face tripling their risk of a potentially fatal or disabling stroke, he speculated.

“Maybe people will get the message,” he said.

Dr. Vieira and all coinvestigators except one reported no relevant conflict of interest. The principal investigator of the study, Dr. Mitchell Elkind, reported support from various pharmaceutical companies. The study is supported by a grant from the National Institute of Neurological Disorders and Stroke.

Betsy Bates is a freelance writer based in Los Angeles.