One of the biggest studies around has proven that scrupulously controlling a diabetic’s blood-sugar can be worth the effort. More than 1,400 people have been followed since 1983, when doctors thought complications from blindness to kidney disease were inevitable side effects of diabetes.

But Dr. William Sivitz, a University of Iowa professor of internal medicine, says the study proved conclusively that the rate of serious complications was three times less in the group that intensively monitored and controlled their blood sugar. And there were other effects they didn’t know about. “Vascular events” — heart attacks, strokes, damage to the big arteries in the legs, were too rare to find out if blood-sugar control would have any effect on those. But after following patients all this time, they’ve said in a report in a recent New England Journal of Medicine that intensive control can reduce those large-vessel complications.

The study never ended — it’s still going on, and the longer doctors follow the diabetic clients, the more they learn, much of it unexpected. So now the researchers know the benefits of careful control may not only spare the eyes, kidneys and nerves, but also benefit the large blood vessels that supply the heart, brain, and feet. The lower the blood sugar, the less the likelihood of developing complications, a pattern that’s taken a long time and a lot of patients to make clear.

Sivitz says they’re also finding out which treatments work best for which people, since many new treatments have been developed. Some patients were treated with several shots of insulin taken throughout the day, some with insulin pumps implanted in the body, and some with newer forms of insulin that preclude the need for the pump. They plan to follow this group for at least another ten years, and expect the National Institutes of Health will continue the funding that allows the 28 research institutions, including University of Iowa, to do it.