Insulin Pump Better than Injections for Some Type 1's

In the largest and longest study ever of an insulin pump with a continuous glucose sensor, patients who used the device achieved better control of their blood sugar than patients taking insulin injections. 

Those in the study who used the insulin pump, marketed by medical device maker Medtronic Inc., had to adjust their insulin levels manually, just as patients who give themselves insulin injections do.

But Medtronic and other companies are working on a closed-loop system -- often referred to as an artificial pancreas -- which will continuously monitor blood sugar levels and adjust insulin delivery automatically.

Study researcher Richard M. Bergenstal, MD, says the new study proves that combining an insulin pump and sensor can help patients achieve optimal blood sugar control even without the automatic insulin delivery.

Bergenstal is executive director of the International Diabetes Center at Park Nicollet, St. Louis Park, MN, as well as president for medicine and science with the American Diabetes Association.

Bergenstal stated that, "We were able to get blood sugar down into the range where we can prevent long-term complications and we did it without causing it to drop too low....  These are probably the best results in terms of balancing the two of any study done to date."

In healthy people, insulin is produced in the pancreas to help the body convert glucose from the diet into energy. People with Type 1 diabetes lose the ability to make their own insulin and most take insulin injections throughout the day.

Poorly controlled frequent high blood sugar leads to the long-term complications of diabetes, including possible blindness, amputation, and kidney failure.

But Bergenstal explains that low blood sugar, known medically as hypoglycemia, is the bigger concern in people who tightly manage their disease with insulin.

"Current treatments are increasingly helping people avoid high blood sugar, but this has resulted in low blood sugar," he says.

The study included 485 people with Type 1 diabetes, ranging in age from 7 to 70, who had been unable to achieve optimal blood sugar control with insulin injections.

Half the patients received standard treatment, which involved testing their blood sugars throughout the day and taking insulin injections when needed. The other half used the pump and glucose sensor device, which delivered insulin through a small catheter inserted under the skin.

The sensor was added only after the patients had become comfortable with the pump, usually after two to five weeks. Patients in both treatment groups also received training to help them better manage their diabetes.

Hemoglobin A1c was monitored to assess blood sugar control. Normal hemoglobin A1c in people without diabetes ranges from 4% to 6%, and the goal for avoiding complications in people with the disease is less than 7%.

After one year of treatment, patients in the pump group had significantly lower hemoglobin A1c levels than those in the insulin injection group. A1c levels in pump patients dropped from an average of 8.3% to 7.5%, while levels dropped to just 8.1% in the insulin injection group.

Adults who used the pump had better outcomes than children and teens, but they were also more likely to use the devices for longer periods.  And even though the pump patients achieved better blood sugar control, the incidence of severe low blood sugar was similar for both groups.

Highly motivated study participants achieved the best blood sugar control. Patients who used the pumps 80% of the time reduced their risk of developing diabetes complications by 30% to 40%, Bergenstal says.

In an editorial accompanying the study, endocrinologist Howard A. Wolpert, MD, of Boston's Joslin Diabetes Center questioned whether the devices would work as well in the general practice setting. "The expert training and guidance received by patients in clinical trials cannot be readily duplicated in a busy clinical practice," he writes. "This technology really does bring diabetes self-management to the next level," he says. "But patients really do need to be pretty skilled in using the information provided by the sensor effectively."

The next generation of pumps that both monitor and deliver insulin automatically are poised to simplify diabetes management. But Wolpert says patient education will still be a critical component of controlling the disease, Wolpert says.

Francine Kaufman, MD, who is vice president of global medical affairs for Medtronic, said the company recently began studies in the U.S. of a pump-sensor device that will automatically stop delivering insulin if blood sugar drops too low. The company is already marketing such a device in Europe, and she says the goal is to win FDA approval in the U.S. within the next several years.

New England Journal of Medicine, July 22, 2010