Nearly 40% of adults with type 1 diabetes not diagnosed until after age 30 years

Key takeaways:

• Of 947 adults, 37% were not diagnosed with type 1 diabetes until after age 30 years.
• Diagnosis was more often delayed among men and diverse racial and ethnic groups.

Almost four in 10 adults with type 1 diabetes were not diagnosed until after the age of 30 years, according to a recently published study.

“Adult-onset type 1 diabetes is frequently misdiagnosed as type 2 diabetes, leading to inappropriate care,” Michael Fang, PhD, MHS, an assistant professor of epidemiology at John Hopkins Bloomberg School of Public Health, and colleagues wrote in the Annals of Internal Medicine. “Emerging data suggest that up to 62% of type 1 diabetes cases develop after age 20 years.”

However, they pointed out that prior studies have been done on only select clinical populations.

“Clarifying the burden of adult-onset type 1 diabetes in the general population may help reduce misdiagnosis,” the researchers wrote.

Fang and colleagues analyzed data from the National Health Interview Survey collected from 2016 to 2022. Their study focused on a cohort of 947 adults with type 1 diabetes, representing about 1.3 million adults in the United States.

Overall, they found that 37% of adults were diagnosed with type 1 diabetes after the age of 30 years. The median age at diagnosis across the entire study population was 24 years.

Additionally, type 1 diabetes was diagnosed later for men than for woman (median age, 27 vs. 22 years) and for adults from diverse racial and ethnic backgrounds vs. non-Hispanic white adults (median age, 26 to 30 vs. 21 years).

The researchers explained that because type 1 diabetes often has mild symptoms, it can be difficult to distinguish from type 2 diabetes.

“Autoantibody and C-peptide testing are recommended for diagnosis in adults suspected of having type 1 diabetes,” they wrote. “However, how to best identify high-risk adults remains unclear.”

Fang and colleagues acknowledged several study limitations. For example, there was possible misclassification due to self-reporting of diabetes type and age at diagnosis, and information about key diagnostic measures were not included in the survey.

“Tools integrating clinical measures and biomarkers may improve the accuracy of diagnosis for these patients,” the researchers concluded.