“This is the first time we’ve put the full spectrum together over a long period of time,” Dr. Gregg said. He pointed out that heart attacks, which used to be the most common complication by far, had dropped down to the level of stroke, which also fell.

“We were a bit surprised by the magnitude of the decrease in heart attack and stroke,” he said.

Beyond the declines in the rates of heart attacks and deaths from high blood sugar, the study found that the rates of strokes and lower extremity amputations — including upper and lower legs, ankles, feet, and toes — fell by about half. Rates for end-stage kidney failure dropped by about 30 percent. The study did not measure blindness, another critical diabetes complication.

Dr. Gregg cautioned, however, that the number of Americans with diabetes continued to rise. “We have to find a way to replicate these successes, to transfer that knowledge into preventing the disease to begin with,” he said.

The declines in rates of complications began around 1995 and continued gradually, but steadily, over time, the data show. What drove the outcomes varied by the complication, Dr. Gregg said. Improved blood sugar control has made a difference, especially in reducing the rate of amputations and end-stage kidney disease. Declines in smoking and the rising use of statins to lower cholesterol and of other medications to control blood pressure contributed to the declines in heart attacks and strokes.

Researchers noted that heart attacks had declined substantially for the general population as well, where the same factors were at work. But while people without diabetes saw a 31 percent decline since 1990, those with it experienced a 68 percent drop.

Dr. Joel Zonszein, director of the Clinical Diabetes Center at the Montefiore Medical Center in the Bronx, attributed much of the improvement to a change in the approach to treatment. Doctors are putting more emphasis on controlling blood pressure and cholesterol — major risk factors for heart disease and strokes — than on lowering blood sugar, he said.

Because cardiovascular disease is what kills most people with diabetes, this shifting priority seems to have paid off. Dr. Zonszein said that certain blood pressure drugs, not available in the past, help protect the kidneys and had helped prevent or at least postpone kidney failure for many patients.