Research Finds Insulin Ineffective For Many Diabetics

"Insulin therapy was found to be largely ineffective in achieving tight blood sugar control, even when combined with substantial increases in a patient's visits to the doctor's office and home blood sugar monitoring," said Rodney Hayward, M.D., leader of the study and an investigator at Veterans Affairs and the University of Michigan Health System.

The study's findings are published in the Nov. 26 issue of the Journal of the American Medical Association.

About nine out of 10 diabetics have type 2 diabetes, which means their pancreases produce some insulin, but not enough to meet their needs. In the U.S. alone, more than nine million people are diagnosed with type 2 diabetes---a leading cause of blindness, renal failure, and amputation in industrialized nations.

Thirty to 40 percent of type 2 diabetics are on insulin in an effort to improve blood sugar control and thereby reduce their risk of the disease's devastating complications. Previous research has demonstrated that carefully selected patients under close supervision can achieve strict blood sugar control with insulin, but this is the first study to evaluate how effective, safe and costly insulin treatment is in a more typical setting---when patient care is less intensive and managed by primary care doctors.

Here is a summary of the study's key findings and their ramifications:

---For type 2 diabetics with poor blood sugar control, starting insulin treatments significantly improved blood sugar control---but rarely approached the commonly recommended goal of near-normal control. "Much more aggressive treatment is needed for the 10 to 15 percent of patients who currently have poor glycemic control," Hayward said, "because, otherwise, they are at high risk of blindness, kidney failure and nerve damage." The study suggests insulin can help many of these patients reach a far safer moderate blood sugar level.

---For patients using pills to control their diabetes and maintaining moderate blood sugar control, administering insulin was only minimally effective, and did not move most patients into the near-normal range for blood sugar. That contradicts previous studies that indicated insulin can achieve tight blood sugar control---but those studies used volunteer subjects who likely were highly motivated to follow their medical regimen and received closer medical supervision and support than occurs in a typical clinical setting. These new findings suggest it would be difficult, troublesome and costly for most type 2 diabetics to achieve the tight control of blood sugar typically recommended.

---Most type 2 diabetics develop the disease later in life and maintain moderate control of their blood sugar, two factors which put them at relatively low risk of developing severe complications such as blindness and renal failure later in life. That risk often is less than one chance in 100.

Given the difficulty diabetics will have achieving the recommended tight control of blood sugar and the fact that most are at relatively low risk of developing serious complications, Hayward suggests the medical profession needs to reconsider whether the standard of tight glycemic control for virtually all diabetics is appropriate or necessary. "Achieving optimal blood sugar control with insulin requires either highly motivated patients, such as those likely to participate in experimental trials, or greater education and monitoring than can be accomplished in a patient's typical two to four annual visits to the doctor's office," Hayward said.

---In a study published earlier this month in the Annals of Internal Medicine, Hayward and colleagues at U-M demonstrated that people who develop type 2 diabetes at a relatively early age---before age 50, for example---are at far greater risk of ultimately losing their vision and kidney function than those whom the disease strikes later.

For those high-risk patients, the new research suggests insulin therapy will not be adequate to achieve the near-normal blood sugar levels needed to help lower their risk. "For this group, tight blood sugar control is a reasonable goal," Hayward said, "but more effective treatment approaches are likely to be needed."

One such treatment that is showing promise, he said, is a combination of insulin given at bedtime and oral medicine administered during the day. "High-risk patients, those who require tight blood sugar control to reduce future health complications, will need closer monitoring and more medical attention than most diabetics typically receive."

For this project, the investigators analyzed insulin use over a three- to four-year period among 1,738 patients treated by generalist physicians participating in a large health maintenance organization.

"Although it is disappointing that blood sugars did not return to near-normal levels on insulin, the results fit well with reports of many doctors with whom we have spoken over the last few years," said Sheldon Greenfield, a co-author of the study and director of the Primary Care Outcomes Research Institute at New England Medical Center and director of the Diabetes Patient Outcomes Research Team National Study, from which this analysis was drawn. "Physicians often feel guilty, frustrated or even inadequate after major efforts that include switching to insulin from an oral medication. They are also worried that national quality of care standards soon to be proposed will call for normalization of sugar in all patients."

The study was funded by the Agency for Health Care Policy and Research.