Global incidence of adult-onset T1D higher than expected

An international study led by researchers from the Chinese University of Hong Kong (CUHK) has shown a higher-than-expected incidence of adult-onset type 1 diabetes (T1D) worldwide, indicating a need for accurate diagnosis of these patients to facilitate appropriate treatment including early insulin therapy.

While T1D can occur at any age, only the epidemiology of childhood-onset T1D is well documented. “The epidemiology of adult-onset T1D and its incidence are, in contrast, less well characterized,” the researchers noted. “Recognition of adult-onset T1D and assessment of trends in its incidence are important, as T1D [in adults] is commonly misclassified as type 2 diabetes [T2D] and often requires treatment very different from that for T2D.” [Diabetes Care 2022;45:994-1006]

In this global systematic review, the researchers analyzed T1D incidence in adults aged ≥20 years based on both population-based studies and the grey literature, such as diabetes registries and national health surveys. A total of 46 reports across 32 countries and regions were analyzed, with 78 percent of the data collected from high-income areas in Europe and the Western Pacific, including Hong Kong.

Overall, there was a substantial incidence of adult-onset T1D worldwide. Five out of 12 studies (42 percent) revealed increasing trends of adult-onset T1D across adult age groups. Although no specific trend of adult-onset T1D incidence was found in Hong Kong, local T1D patients ≥20 years of age accounted for 68.1 percent of all newly diagnosed T1D cases. [PLoS Med 2020;17:e1003052]

“Of note, the number of new [T1D] cases did not decline with age, highlighting the significant incidence of T1D diagnosed in later life,” stated senior author Professor Ronald Ma of the Department of Medicine and Therapeutics, CUHK.

This study also showed an association of adult-onset T1D with gender and geographical regions. Among 26 reports analyzed, 24 revealed that men were more likely than women to have adult-onset TD1. Furthermore, the rate of adult-onset T1D was higher in the Nordic population than the Asian population. Some data from the study have been published in the International Diabetes Federation Diabetes Atlas 2021. [https://diabetesatlas.org/atlas/tenth-edition/]

“This is an updated and comprehensive overview of the current knowledge on adult-onset T1D," the researchers noted. “Nevertheless, we believe the incidence rates of adult-onset T1D are still likely to be underestimates in general, given the likelihood of missed cases among those presenting in adulthood.”

“The major challenge is the identification of underlying T1D in adults presenting with diabetes. This is the key to T1D [adult] patients receiving appropriate treatment, especially early insulin therapy,” Ma added.

The incidence of type 1 diabetes in the world. Adapted from International Diabetes Federation Diabetes Atlas 2021