The number of U.S. diabetics with healthy blood sugar levels has declined in recent years, a study suggests.
Researchers analyzed data on 1.6 million adults with diabetes from 2006 to 2013. During this period, the proportion with HbA1c below 7 percent declined from 56 percent to 54 percent, and the share with HbA1c at or above 9 percent rose from 10 percent to 12 percent.
"Clearly, there is a sizeable proportion of patients with poor glycemic control - and many of them are young," said lead study author Kasia Lipska of Yale University in New Haven, Connecticut. "We need to do better for them."
The researchers examined data on prescriptions and blood sugar test results to see how changes in medication utilization might relate to shifts in the proportion of diabetics with healthy blood sugar.
Use of thiazolidinediones plummeted from 2006 to 2013 when one drug in this class (rosiglitazone) was linked to an increased risk of heart attack, stroke and congestive heart failure. Thiazolidinedione prescriptions accounted for less than 6 percent of the market share for diabetes drugs by the end of the study period, down from 29 percent at the start.
Prescriptions also fell for sulfonylureas. These medicines accounted for 31 percent of prescriptions at the end of the study, down from 39 percent.
Meanwhile, DPP-4 inhibitors, introduced around the start of the study period, accounted for 15 percent of prescriptions by 2013. (These drugs include sitagliptin, saxagliptin and vildagliptin, for example.)
Prescriptions for metformin rose from 48 percent to 54 percent over the course of the study.
The study didn't explore why shifts in drug utilization or changes in glycemic control occurred, but it's possible at least some patients were using less effective medicines by the end of the study, Lipska said by email.
"Many of the newer medications have the advantages of not causing weight gain or hypoglycemia, however, some are not as potent in lowering blood sugar levels as many of the older medications," Lipska said.
"In addition, just because medications are available and put into use doesn't mean that they are necessarily applied in ways that improve care," Lipska added.
One limitation of the study is its focus on people with private insurance or Medicare who may be more likely to take expensive newer medicines than uninsured patients, the authors note in Diabetes Care, online September 22.
Another drawback is that researchers only had blood sugar data for about 25 percent of the people in the study, noted Dr. David Nathan, director of the Massachusetts General Hospital Diabetes Center in Boston.
"Other data have suggested a major improvement in diabetes control over the past 20 years," Nathan, who wasn't involved in the study, said by email.
Recently, however, despite the introduction of new drugs, improvement in blood sugar control has leveled out, Nathan said. "The new medicines are substantially more expensive without obvious benefits."
With so many drugs to choose from, it's also possible people are overlooking the role of diet and exercise in managing the disease, said Dr. William Herman, a researcher at the University of Michigan in Ann Arbor who wasn't involved in the study.
"Obesity and lack of focus on diet and physical activity may certainly be contributing to the lack of improvement in blood sugar control," Herman said by email.