BOSTON (AP) _ To doctors' disappointment, a landmark study has found that preventive injections of insulin do not ward off a common form of diabetes.
The idea of preventing diabetes with insulin has been considered for decades. More recently, animal research and small studies with people suggested it would work for type 1 diabetes. Some doctors were already giving insulin to patients in the hope of preventing it.
``The history of medicine is littered with wrong conclusions drawn from pilot studies,'' said Dr. Jay Skyler, a hormone specialist at the University of Miami who led the study, which was funded by the National Institutes of Health.
The preliminary findings were reported in Thursday's New England Journal of Medicine.
Up to 1 million Americans have the disease, formerly known as juvenile diabetes, and face a lifetime of taking insulin. The body's defenses attack the pancreas' ability to make insulin, a substance that processes sugar. People at high risk for type 1 diabetes can be identified from antibodies and other testing.
In theory, preventive insulin could either rest the body's insulin cells and thus make them stronger, or retool the immune system to stop its assault on the pancreas.
More common type 2 diabetes _ in which the body cannot process insulin correctly _ would be beyond the reach of preventive insulin.
Of 84,228 screened for the study, 339 were identified with a five-year risk of more than 50 percent of developing diabetes. They were randomly assigned to undergo insulin injections or just monitoring. Both groups developed the disease at an annual rate of about 15 percent.
The research team is still working on preventing type 1 diabetes with an insulin pill, which is thought to work by a different mechanism. Those findings could come next year.
Dr. Richard Jackson, a study supervisor at Boston's Joslin Diabetes Center, said he holds ``reasonable hope'' for success with the pill. ``If we look at the history of clinical research, it's rare that the first arrow hits the target,'' he said.
A separate study in the journal did offer some hope for people with the type 1 disease.
The researchers found that a drug designed from an immune-system antibody known as OKT3 can arrest the disease in its early stages for at least a year. However, the drug is not expected to delay the disease indefinitely.
Twelve patients were treated in this preliminary test supervised at Columbia University. Nine kept their ability to make insulin.