Depression, insulin regimen linked to poor diabetes control

In the largest study of diabetes and depression conducted to date, researchers at Duke University Medical Center have found a clear link between the complexity of the self-care regimens in patients with diabetes and the effect of depression on diabetes control. They said the findings could help settle a long-standing debate among clinicians over whether a link between depression and diabetes control exists.

According to the researchers, depressed diabetic patients who take three or more insulin shots per day are at much greater risk of being in poor metabolic control than are depressed patients who require no insulin or less insulin. While depression only affects diabetes control in some patients, those who require higher amounts of insulin should pay more strict attention to symptoms of depression, they added.

"We know that patients who require more insulin on a daily basis have less residual pancreatic activity and a more difficult time regulating their glucose levels," said Richard Surwit, Ph.D., vice-chairman of research in the department of psychiatry and behavioral medicine at Duke. "Their metabolic control is going to be more vulnerable to disruption by behavioral and neuroendocrine factors. This means that at any level of depression, diabetics who experience more difficulty regulating their glucose levels are more likely to get thrown even farther off balance by depression."

Surwit prepared his group's findings for presentation June 5, 2004, at the 64th annual scientific sessions of the American Diabetes Association.

More than 1,000 adults 18 years or older with diabetes were recruited to participate in the study. The participants were all members of a local Health Maintenance Organization (HMO) in Durham, N.C. The HMO contacted all diabetes patients they were serving and invited them to participate. Of the 1,034 patients who agreed, at their next routine examination all were administered a hemoglobin A1c (HbA1c) test to measure their glucose levels. Afterward, patients were sent a depression assessment form, called a Beck Depression Inventory.

Surwit's research team compared the relationship of depression to diabetes control among participants based upon treatment regimens. The patients fell into natural groupings based on their treatment programs:

• diet and exercise only
• oral medications only
• oral medications and insulin
• one to two insulin injections daily
• three or more daily injections of insulin

The researchers found no correlation between depressive symptoms and glycemic control in patients taking fewer than three insulin shots per day, regardless of their type of diabetes. However, there was a strong correlation between depressive symptoms and glycemic control in those patients with the more complex regimen of taking three or more insulin shots per day.

"Patients who have more complex self-care regimens, particularly those who are taking three or more insulin shots per day should pay close attention to shifts in mood," Surwit added. "And physicians who are treating people who fall into this category should be regularly monitoring them for signs of depression. Depression is treatable, but left untreated the greater the patient's vulnerability to extreme glucose fluctuations."

According to 2002 statistics provided by the National Institute of Diabetes & Digestive & Kidney Diseases, approximately 18.2 million people in the U.S. have diabetes, at a total direct and indirect cost of $132 billion per year. Complications of diabetes include heart disease and stroke, high blood pressure, blindness and kidney disease. Previous research has shown that approximately 30 percent of adult patients with diabetes report experiencing clinically significant depressive symptoms. Depressive symptoms in these patients are associated with reduced quality of life, impaired physical functioning, increased diabetic complications and increased medical costs.

Research funding was provided through an educational grant from Pfizer, Inc. but the grant was not used to examine any Pfizer product or service.

Other authors on the study include Miranda A.L. Van Tilburg, Ph.D.; Priti I. Parekh, Ph.D.; James D. Lane, Ph.D. and Mark Feinglos, M.D.. Surwit owns stock in Pfizer, Inc.

Surwit is author of "The Mind-Body Diabetes Revolution: A Proven New Program for Better Blood Sugar Control," published in 2004 by Free Press, a subsidiary of Simon & Schuster, Inc.