Glycemic Control With Insulin Barely Budged Over the Past 30 Years

Rates of insulin-treated adults achieving glycemic control in the U.S. were stagnant over the past 3 decades, according to National Health and Nutrition Examination Survey data.

Of 2,482 adults ages 20 and older using insulin for their diabetes, a total of 29.2% were achieving glycemic control targets from 1988-1994 compared with 27.5% from 2013-2020, a non-significant change, Elizabeth Selvin, PhD, MPH, of Johns Hopkins Bloomberg School of Public Health in Baltimore, and colleagues found.

While the overall rate of glycemic control remained flat, the average duration of diabetes increased from 12.9 years up to 17.8 years, the group reported in JAMA Network Open.

The average adult with insulin-treated diabetes also had a significantly higher body mass index in recent times compared with 30 years ago, rising from an average of 30.1 to 33.4.

Although the average age of adults with diabetes using insulin remained relatively the same between the two time periods (60.1 years in 1988-1994 vs 60.6 years in 2013-2020), the proportion of men treated with insulin increased (41.7% to 54.9%) while the proportion of women decreased (58.3% to 45.1%).

But looking more closely at age differences, adults 65 and older were more likely to achieve glycemic control on insulin and less likely to experience severe hyperglycemia than younger adults with diabetes.

During this time, the proportion of adults with diabetes using insulin who were Mexican American more than doubled, from 4.2% to 9%. On the other hand, there was a steady decline in the proportion of Black adults (21.5% to 14.9%) as well as white adults (70.8% to 63.2%). That being said, glycemic control significantly dropped for Mexican American adults treated with insulin during this time, falling from 25.1% to 9.9% by 2020.

When racial and ethnic groups were compared, Mexican American adults treated with insulin were significantly less likely to achieve glycemic control than were white adults (OR 0.45, 95% CI 0.30-0.68).

In terms of all racial groups, overall rates of severe hyperglycemia — defined as an HbA1c over 10% — generally remained the same (18.2% vs 14.6%), as did average HbA1c level, which held steady at 8.1%. However, the rates of severe hyperglycemia persistently remained much higher over time for Mexican Americans (23.9%) and Black adults (22.7%) compared with white adults (9.1%). Black adults were 2.48 times and Mexican Americans were 2.29 times more likely than white adults to experience severe hyperglycemia while treated with insulin.

“These disparities may be driven in part by differences in socioeconomic resources, though differences persisted in analyses that adjusted for educational level,” Selvin’s group wrote. “Other potential contributors may include unique cultural factors and health beliefs (e.g., fear of needles), slower treatment intensification, differences in health care literacy, and discrimination.”

“Improving diabetes care among Mexican American adults may require culturally tailored interventions,” the researchers suggested.

Among this patient population, public or other insurance other than private insurance became far more popular from 1988 to 2020, with rates nearly doubling from 23.8% to 42%.

Taken together, there are likely several factors driving this lack of improvement in glycemic control, Selvin and co-authors noted. “First, the rising cost of insulin is likely leading to medication nonadherence. Approximately one-third of US adults using insulin report either rationing, dose skipping, or delaying prescription refills to save money.”

“Second, only a small proportion of practitioners may be starting or intensifying insulin therapy in a timely manner,” the researchers added. Another reason could also be due to the persistently low acceptability of insulin among patients, leading to many being quite reluctant to begin or continue using insulin as recommended by their healthcare provider.

Selvin’s group recommended that practitioners “address clinical inertia” and “improve the care process” in order to optimize glycemic control among patients using insulin.