Global incidence, prevalence, and mortality of type 1 diabetes in 2021 with projection to 2040: a modelling study br

Background Accurate data on type 1 diabetes prevalence, incidence, associated mortality and life expectancy are crucial to inform public health policy, but these data are scarce. We therefore developed a model based on available data to estimate these values for 201 countries for the year 2021 and estimate the projected prevalent cases in 2040.Methods We fitted a discrete-time illness-death model (Markov model) to data on type 1 diabetes incidence and type 1 diabetes-associated mortality to produce type 1 diabetes prevalence, incidence, associated mortality and life expectancy in all countries. Type 1 diabetes incidence and mortality data were available from 97 and 37 countries respectively. Diagnosis rates were estimated using data from an expert survey. Mortality was modelled using random -forest regression of published type 1 diabetes mortality data, and life expectancy was calculated accordingly using life tables. Estimates were validated against observed prevalence data for 15 countries. We also estimated missing prevalence (the number of additional people who would be alive with type 1 diabetes if their mortality matched general population rates).Findings In 2021, there were about 8middot4 (95% uncertainty interval 8middot1-8middot8) million individuals worldwide with type 1 diabetes: of these 1middot5 million (18%) were younger than 20 years, 5middot4 million (64%) were aged 20-59 years, and 1middot6 million (19%) were aged 60 years or older. In that year there were 0middot5 million new cases diagnosed (median age of onset 39 years), about 35 000 non-diagnosed individuals died within 12 months of symptomatic onset. One fifth (1middot8 million) of individuals with type 1 diabetes were in low-income and lower-middle-income countries. Remaining life expectancy of a 10-year-old diagnosed with type 1 diabetes in 2021 ranged from a mean of 13 years in low-income countries to 65 years in high-income countries. Missing prevalent cases in 2021 were estimated at 3middot7 million. In 2040, we predict an increase in prevalent cases to 13middot5-17middot4 million (60-107% higher than in 2021) with the largest relative increase versus 2021 in low-income and lower-middle-income countries.Interpretation The burden of type 1 diabetes in 2021 is vast and is expected to increase rapidly, especially in resource -limited countries. Most incident and prevalent cases are adults. The substantial missing prevalence highlights the premature mortality of type 1 diabetes and an opportunity to save and extend lives of people with type 1 diabetes. Our new model, which will be made publicly available as the Type 1 Diabetes Index model, will be an important tool to support health delivery, advocacy, and funding decisions for type 1 diabetes.Funding JDRF International.Copyright (c) 2022 Published by Elsevier Ltd. All rights reserved.