The T1D Index: Implications of Initial Results, Data Limitations, and Future Development.

PURPOSE OF THE REVIEW: Current global information on incidence, prevalence, and mortality of type 1 diabetes (T1D) is limited, particularly in low- and middle-income countries. To address this gap in evidence, JDRF, Life for a Child, International Society for Pediatric and Adolescent Diabetes, and International Diabetes Federation have developed the T1D Index, which uses a Markov mathematical model, and machine learning and all available data to provide global estimates of the burden on T1D. This review assesses the methodology, limitations, current findings, and future directions of the Index. RECENT FINDINGS: Global prevalence was estimated at 8.4 million in 2021, with 1.5 million <20 years (y). T1D prevalence varied from 1.5 to 534 per 100,000, with T1D accounting for <0.1-17.8% of all diabetes in different countries. A total of 35,000 young people <25 y are estimated to have died at clinical onset of T1D from non-diagnosis. An estimated 435,000 people <25 y were receiving "minimal care." Health-adjusted life years (HALYs) lost for individuals diagnosed with T1D at age 10 y in 2021 ranged from 14 to 55 y. These results show that interventions to reduce deaths from non-diagnosis, and improve access to at least an intermediate care level, are needed to reduce projected life years lost. The results have significant uncertainties due to incomplete data across the required inputs. Obtaining recent incidence, prevalence, and mortality data, as well as addressing data quality issues, misdiagnoses, and the lack of adult data, is essential for maintaining and improving accuracy. The index will be updated regularly as new data become available.

Costs and outcomes of "intermediate" vs "minimal" care for youth-onset type 1 diabetes in six countries.

OBJECTIVE: Data are needed to demonstrate that providing an "intermediate" level of type 1 diabetes (T1D) care is cost-effective compared to "minimal" care in less-resourced countries. We studied these care scenarios in six countries. METHODS: We modeled the complications/costs/mortality/healthy life years (HLYs) associated with "intermediate" care including two blood glucose tests/day (mean HbA1c 9.0% [75 mmol/mol]) in three lower-gross domestic product (GDP) countries (Mali, Tanzania, Pakistan), or three tests/day (mean HbA1c 8.5% [69 mmol/mol]) in three higher-GDP countries (Bolivia, Sri Lanka, Azerbaijan); and compared findings to "minimal" care (mean HbA1c 12.5% [113 mmol/mol]). A discrete time Markov illness-death model with age and calendar-year-dependent transition probabilities was developed, with inputs of 30 years of complications and Standardized Mortality Rate data from the youth cohort in the Pittsburgh Epidemiology of Diabetes Complications Study, background mortality, and costs determined from international and local prices. RESULTS: Cumulative 30 years incidences of complications were much lower for "intermediate care" than "minimal care", for example, for renal failure incidence was 68.1% (HbA1c 12.5%) compared to 3.9% (9%) and 2.4% (8.5%). For Mali, Tanzania, Pakistan, Bolivia, Sri Lanka, and Azerbaijan, 30 years survival was 50.1%/52.7%/76.7%/72.5%/82.8%/89.2% for "intermediate" and 8.5%/10.1%/39.4%/25.8%/45.5%/62.1% for "minimal" care, respectively. The cost of a HLY gained as a % GDP/capita was 141.1%/110.0%/52.3%/41.8%/17.0%/15.6%, respectively. CONCLUSIONS: Marked reductions in complications rates and mortality are achievable with "intermediate" T1D care achieving mean clinic HbA1c of 8.5% to 9% (69-75 mmol/mol). This is also "very cost-effective" in four of six countries according to the WHO "Fair Choices" approach which costs HLYs gained against GDP/capita.

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

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 8·4 (95% uncertainty interval 8·1-8·8) million individuals worldwide with type 1 diabetes: of these 1·5 million (18%) were younger than 20 years, 5·4 million (64%) were aged 20-59 years, and 1·6 million (19%) were aged 60 years or older. In that year there were 0·5 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 (1·8 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 3·7 million. In 2040, we predict an increase in prevalent cases to 13·5-17·4 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.