Intensive type 1 diabetes control cuts complications over the long term

People with type 1 diabetes who stick to a strict regimen to keep their blood sugar levels near normal can reduce their risk of serious complications, according to a large study that followed patients who had the disease for 30 years. The trial is the longest and largest to track such tight control since it became the standard of care in 1993.

In type 1 diabetes, which accounts for 5 to 10 percent of all diabetes, the body no longer makes insulin, the hormone that regulates blood sugar levels. Patients, who must inject insulin daily to stay alive, are more vulnerable than other people to kidney failure, vision loss, heart disease, and nerve damage that sometimes leads to amputation.

A landmark study that appeared in 1993 showed that closely monitoring blood sugar levels, injecting insulin at least three times a day, and carefully calibrating insulin doses to match diet and activity could substantially cut the risk of these serious conditions. Conventional therapy until then called for one or two insulin injections a day and a daily blood or urine test for blood sugar.

Dr. David M. Nathan, director of the Diabetes Center at Massachusetts General Hospital, said that study is widely viewed as the most important since the introduction of insulin. He is the lead author of the new study in today's Archives of Internal Medicine that builds on that work to show what modern therapies based on tight control mean for people with type 1 diabetes.

Following patients from that earlier trial and comparing them to patients diagnosed between 1950 and 1980, Nathan and his colleagues report that more-intensive blood sugar control was associated with a significantly lower risk of complications. For vision loss, the rate was 21 percent among tight-control patients compared to 50 percent among the earlier patients. For kidney damage, the rate was 9 percent in tight control patients versus 25 percent for the earlier patients. For cardiovascular disease, the rate was 9 percent in tight control group compared to 14 percent in the earlier group.

The authors acknowledge the possible effect that better medical care, including blood pressure and cholesterol control, might have had on later patients' health. They also say that direct comparisons over two time periods are difficult, but differences are clear. For Nathan, the study will help patients have a clearer idea of what may lie ahead for them.

"We can now look at our type 1 diabetes patients and tell them after an average of 30 years what will happen if they follow the intensive therapy we recommend," he said in an interview. "This should be even further reason for people to follow this intensive therapy."

Such intensive therapy is not easy, he said, but insulin pumps and more rapidly absorbed forms of insulin help patients get closer to their goals.

"The challenge we have going forward is to make this even easier and [more] accessible so there isn't anyone who misses out on the opportunity to live a long and healthy life," he said.

Type 1 diabetes results when the body's immune system kills the cells that make insulin. It is different from the much more common type 2 diabetes, which develops more often in people who are older, obese, or have a family history of diabetes.

The multicenter study, which included Joslin Diabetes Center as well as Mass. General, was funded by the National Institutes of Health.