The Incidence of Adult-Onset Type 1 Diabetes: A Systematic Review From 32 Countries and Regions

Abstract

<i>Background: </i>The epidemiology of adult-onset type 1 diabetes (T1D) incidence is not well characterized due to the historic focus on T1D as a childhood-onset disease. <a></a> <p> </p> <p><i>Purpose</i>: We assess the incidence of adult-onset (≥20 years) T1D, by country, from available data. </p> <p> </p> <p><i>Data sources:</i> A systematic review of Medline, Embase, and the grey literature, through May 11, 2021, was undertaken. </p> <p> </p> <p><i>Study selection:</i> We included all population-based studies reporting on adult-onset T1D incidence and published from 1990 onwards in English. </p> <p> </p> <p><i>Data extraction:</i> The search identified 1,374 reference of which 46 were included for data extraction. Estimates of annual T1D incidence were ascribed into broad age categories (20–39, 40–59, ≥60, or ≥20 years) as appropriate. </p> <p> </p> <p><i>Data Synthesis: </i>Overall, we observed the following patterns: 1) there is a paucity of data, particularly in low-and middle-income countries; 2) the incidence of adult-onset T1D is lowest in Asian and highest in Nordic countries; 3) adult-onset T1D is higher in men vs. women; 4) it is unclear if adult-onset T1D incidence declines with increasing age; and 5) it is unclear if incidence of adult-onset T1D has changed over time.</p> <p> </p> <p><i>Limitations</i>: Results are generalizable to high-income countries, and misclassification of diabetes type cannot be ruled out.</p> <p> </p> <p><i>Conclusions: </i><a></a><a>From available data, this systematic review suggests that the incidence of T1D in adulthood is substantial </a><a></a>and highlights the pressing need to better distinguish T1D from T2D in adults so that we may better assess and respond to the true burden of T1D in adults.<i></i></p>