A cross-sectional report suggests that more than half of adults with type 1 diabetes received these diagnoses after adolescence.

Type 1 diabetes occurs when the immune system attacks and destroys the insulin-producing beta cells of the pancreas. Type 1 diabetes develops in some patients during adulthood, and as many as 40% of adults who are diagnosed with type 1 diabetes initially were misdiagnosed with type 2 diabetes (Diabetes Care 2021; 44: 2589-2625). Investigators used data from the US National Health Interview Survey (from 2016 to 2022) to identify nearly 1000 adults with self-reported type 1 diabetes to determine their age at diagnosis.

Median age at type 1 diabetes diagnosis was 24 years, with more than one-third of respondents receiving type 1 diabetes diagnoses at age 30 years or older. Type 1 diabetes was diagnosed later in men than in women (median age, 27 vs 22 years), and later in individuals from racial and ethnic minorities than in non-Hispanic whites (median age, 28 vs 21 years).

Comment: Although this cross-sectional study is based on self-reported information and could be subject to misclassification or recall biases, its results are consistent with other reports suggesting that the onset of type 1 diabetes in adulthood is common (Lancet Diabetes Endocrinol 2022; 10: 741-760). Clinicians should consider confirmatory diagnostic testing (e.g. autoantibodies, C-peptide level) when type 1 diabetes is suspected in adults, especially when adults with presumed type 2 diabetes present with type 1 features (e.g. mild diabetic ketoacidosis).

Daniel D. Dressler, MD, MSc, MHM, FACP, Professor of Medicine, Emory University School of Medicine, Atlanta, USA.

Fang M, et al. Age at diagnosis in U.S. adults with type 1 diabetes. Ann Intern Med 2023 Sep 26; e-pub (https://doi. org/10.7326/M23-1707).

This summary is taken from the following Journal Watch titles: General Medicine, Ambulatory Medicine, Hospital Medicine.