An estimated 8.4 million people were living with Type 1 Diabetes (T1D) across the globe in 2021, according to the results of a new modelling study published in The Lancet Diabetes & Endocrinology. This number is predicted to increase to 13.5-17.4 million people living with T1D by 2040.
“Given that prevalence of people with T1D is projected to increase in all countries to up to 17.5 million cases in 2040, our results provide a warning for substantial negative implications for societies and healthcare systems. There is an opportunity to save millions of lives in the coming decades by raising the standard of care for T1D (including ensuring universal access to insulin and other essential supplies) and increasing awareness of the signs and symptoms of T1D to enable a 100% rate of diagnosis in all countries. Our model, which will be made available open-source, will make data on the burden of T1D widely accessible and serve as a platform for stakeholders to make improvements in T1D care and outcomes,” says Prof. Graham Ogle, one of the authors of the study, Sydney Medical School, University of Sydney, Australia. 
Data on T1D prevalence and mortality is rarely available in most countries – missing data usually relates to LMICs and adult populations, with most previous studies calculating T1D incidence based on European and North American data. The 2017 Lancet Diabetes & Endocrinology Commission on Diabetes in sub-Saharan Africa , WHO, and WHA have all stated an urgent need for worldwide data on T1D. This new study aims to answer these calls, providing modelling estimates that are highly comparable to observed data and estimating missing prevalence for the first time, providing a more meaningful basis for change in T1D care and policy. The results will be made publicly available in an open-source database as part of the T1D Index Project , aimed at assisting health planners, professionals, and advocates to improve care and health outcomes.
Researchers modelled data on childhood, adolescent and adult T1D prevalence in 97 countries, along with incidence over time data from 65 countries and mortality data from 37 countries to predict T1D incidence, prevalence, and mortality in 2021 for 201 countries, with projections of future prevalence through 2040. The estimates were tested for accuracy against real world prevalence data from 15 countries.
In 2021, the model estimated that 8.4 million individuals worldwide were living with T1D. Of these individuals, 18% were under 20 years old, 64% were between 20-59 years, and 19% were over 60 years. Although historically T1D has been a disease associated with onset in childhood, these results reveal that numerically more adults than children are diagnosed every year (316,000 vs 194,000 incident cases worldwide in 2021), with a mean diagnosis age of 32 years.
“These findings have important implications for diagnosis, models of care, and peer support programs. Such programs, in countries where they exist, are almost exclusively designed, and delivered for children and youth with T1D. In addition, our findings emphasise the urgent need for enhanced surveillance and data collection on T1D incidence, prevalence, and mortality in adult populations – an area where data are especially scarce,” says Prof. Dianna Magliano, one of the authors of the study, Monash University, School of Public Health and Preventive Medicine, Melbourne Australia. 
The ten countries with the highest estimated T1D prevalence USA, India, Brazil, China, Germany, UK, Russia, Canada, Saudi Arabia, and Spain account for 5.08 million (60%) of global cases of T1D. Model estimates also suggest that 21% of individuals with T1D live in LICs and LMICs.
Model estimates place global deaths due to T1D at 175,000 in 2021. Of these, 35,000 or 20% were attributed to non-diagnosis, of which 14,500 were in sub-Saharan Africa and 8,700 were in South Asia. The researchers estimate that an extra 3.1 million people would have been alive in 2021 if they hadn’t died prematurely due to suboptimal care of T1D, and a further 700,000 people would still be alive if they hadn’t died prematurely due to non-diagnosis.
“Our findings indicate that the overall footprint of T1D is much larger than previous estimates have indicated, when missing prevalence due to excess mortality is accounted for. This is particularly true in low- and middle-income countries – for example in sub-Saharan Africa which accounts for 357,000 cases of T1D or 4% of global prevalence but 23% (40,000) of the lives lost each year – highlighting the urgent need to increase awareness of the signs and symptoms of T1D in LMICs,” says Prof. Kim Donaghue, one of the authors of the study, Sydney Medical School, University of Sydney, Australia. 
The projected T1D prevalence in 2040 given by the model was is 13.5-17.5 million people, with largest relative increases predicted to occur in LICs and LMICs. Conservative estimates place the relative increase in the number of people living with T1D by 2040 compared to 2020 at 66%.
“We hope that these country-level modelling results will be used by policy makers, researchers, and healthcare professionals alike to build initiatives that improve surveillance of T1D worldwide and encourage Universal health coverage programs, so that T1D care is available and affordable to all, addressing the substantial global burden of this disease,” says Mr Tom Robinson, one of the authors of the study, Juvenile Diabetes Research Foundation, Australia. 
The authors acknowledge some limitations with this study, including a lack of data to input into the model. Data is more limited for adult populations, in LMICs, and before 1975. Information obtained based on extrapolation from nearby countries may be less accurate depending on genetic and environmental factors. In addition, estimate of rates of death from non-diagnosis are based on clinician impressions and are likely to be higher or lower than the actual situation. For mortality rates in diagnosed cases, information is scarce before 1980.
Writing in a linked Comment, Hui Shao, University of Florida, USA (who was not involved in the study), said: “The increasing global burden of Type 1 diabetes […] calls for worldwide actions to alleviate the insulin access and affordability issues. Potential solutions are multifaceted, many of which depend on the country’s political and economic environment. In brief, countries need to strengthen the price regulation and reimbursement policy of insulin while building subsidy programs to ensure insulin access and cope with the growing demand for insulin.”