We are losing ground on diabetes in the United States, and we need to know why.

Although complication rates fell among diabetic patients in the U.S. between 1990 and 2010, a recent Viewpoint in JAMA found a nationwide increase in diabetes complications in recent years. An increase in diabetes-related lower-extremity amputations (LEAs) between 2010 and 2015 reversed more than one-third of a 20-year decline in just five years. Complications related to hyperglycemic crisis (that is, out-of-control blood sugar) also increased — annual emergency department visits almost doubled between 2009 and 2015, hospitalizations increased by 73 percent, and deaths rose by 55 percent for the same period. The rebound in complication rates is most apparent in younger adults (18 to 44), although those in middle age (45 to 64) have higher absolute rates and account for most of the increase.

What explains these new trends? The answer is likely complicated because numerous factors, from patients’ characteristics to policy changes, impact chronic conditions like diabetes.

First, the mix of patients with diabetes has changed, including more young people with higher levels of complicating problems like obesity, smoking, and hypertension. Second, standards for what constitutes adequate blood sugar control have been relaxed among patients with Type 2 diabetes. Reduced access to routine diabetic care because of increased deductibles in employer-sponsored health plans could be a third factor. Repeated visits needed to monitor and dress diabetic foot ulcers and other problems could pose a substantial financial burden. Inadequately treated, such ulcers can advance to require lower extremity amputation.

Partly as a result of those increased deductibles, which often lead people to delay or skip essential care for chronic illness, an estimated 23 percent of working-age adults (44 million people) were underinsured in 2016, up from 16 percent (29 million individuals) in 2010, according to a recent Commonwealth Fund survey. High deductibles hit low-income Americans the hardest, because they are more likely to delay or forgo care rather than face high costs.

Increasing health costs may be further contributing to rising diabetic complication rates. A quarter of diabetic patients who take insulin reported using less than their prescribed dose because of cost, according to a 2019 review in the New England Journal of Medicine. The cost of insulin almost doubled between 2012 and 2016: a patient with Type 1 diabetes incurred annual insulin costs of $5,705, on average, in 2016, up from $2,864 in 2012.

Pharmaceutical companies may justify the increases in insulin prices, like other drugs that have experienced sharp price inflation, as necessary to support innovation. But in this case, any future innovation supported by increased drug prices may be coming at the cost of heart attacks, strokes, and amputations among current diabetics.

The impact of increased cost-sharing and health care costs on diabetes-related complications has not been confirmed, and requires further research, but underscores one of the biggest challenges facing the U.S. health system: high out-of-pocket expenditures can adversely affect the health of patients with chronic conditions. Research to identify why progress has slowed for American diabetics is urgently needed.

This is particularly critical as rising health care costs make having a chronic illness more financially burdensome, as we are witnessing the reversal of a decades-long improvement in health for people with one of our most common chronic illnesses.