The Changing Epidemiology of Type 1 Diabetes: A Global Perspective

Abstract

The prevalence of type 1 diabetes is increasing, with significant implications for public health systems worldwide. This review provides a global overview of the current epidemiology of type 1 diabetes, examining the trends, risk factors, and regional variations in incidence. We explore the influence of genetic, environmental, and socio‐economic factors on the rising incidence of type 1 diabetes. The review also highlights temporal trends in the management of type 1 diabetes and the risk of mortality and morbidity from acute and long‐term complications, including hypoglycaemia, diabetic ketoacidosis, and retinopathy. By synthesizing global and regional data, we aim to provide valuable insights for local health service planning, disease prediction, and tailored interventions. This article underscores the importance of continued research into the epidemiology of type 1 diabetes to better inform prevention, treatment, and management strategies of this growing global health challenge.

Plain Language Summary

Type 1 diabetes (T1D) is an autoimmune condition that begins silently, with the body attacking insulin‐producing cells in the pancreas. This process occurs in two early, silent stages, detectable through blood tests for antibodies, before symptoms appear. It eventually progresses to stage 3, when symptoms develop and insulin treatment becomes necessary.

Prevalence

T1D affects about 9 million people globally, including over 1.5 million children. In addition to those with symptoms, many children and adults may unknowingly have early stage T1D. These can be detected through screening and are estimated to affect around 0.3% of the population.

Incidence

In 2024, there were over 500,000 new diagnoses of T1D worldwide, with cases increasing each year. Rates vary by region, age, and sex. Most diagnoses occur in childhood or early adulthood, with a peak around puberty, though it can develop later in life. Rates are highest in high‐income countries such as Finland and Australia. Lower rates in other regions may reflect limited surveillance. Some countries have reported fluctuating trends, possibly linked to infections. Improved awareness and diagnostics explain and changing risk factors may also play a role.

Risk Factors

The risk of T1D is impacted by genetic, demographic, and environmental factors. Family history increases risk, though the majority of people diagnosed don’t have a family history. Genetic risk scores can also help identify children at higher risk. Risk changes with age, early signs often appear before age 3, and younger children tend to progress more quickly. Two childhood diagnosis peaks occur at ages 4–7 years and 10–14 years. Researchers are exploring possible subtypes of T1D based on age and disease behaviour. White European populations have the highest rates, but increases are also seen in other groups. Environmental factors like viral infections, caesarean birth, and early diet are being studied.

Complications

Managing T1D is complex, however poor control can lead to short‐term emergencies like hypoglycaemia or diabetic ketoacidosis (DKA), and long‐term complications affecting the eyes, kidneys, and nerves. In recent decades, treatment has improved with better insulin regimens and technologies such as insulin pumps, continuous glucose monitors, and hybrid closed‐loop systems. These reduce complications and improve quality of life. Yet challenges remain, including high DKA rates at diagnosis—especially in young children and ethnic minorities, and high diabetic retinopathy rates that can impact vision. Early, tight glucose control reduces long‐term risks, but people with T1D still face a higher risk of early death.

Future Research Directions

Major research gaps remain, especially in low‐ and middle‐income countries. Data on early‐stage and adult‐onset T1D is limited but improving. As new therapies emerge, like teplizumab which is used to delay progression to stage 3, disease patterns may shift. Long‐term data from modern technologies is still developing, with linked administrative data offering a promising solution.

Conclusion

T1D is rising globally and still carries serious health risks. Understanding who is affected, when, and how the disease progresses is essential to improving prevention, care, and outcomes.

1. INTRODUCTION

Type 1 diabetes is an autoimmune condition whereby the insulin‐producing beta cells of the pancreas are progressively destroyed. It develops through two ‘silent’ presymptomatic stages (stage 1 and stage 2), detectable through the presence of two or more persistent islet autoantibodies, before progressing to the overt condition (Stage 3), characterized by hyperglycaemia and the need for insulin therapy (at least by Stage 3b) ¹ , ² (Figure 1).

FIGURE 1.

Stages of type 1 diabetes with the estimated proportion of undiagnosed young children in each stage and the estimated risk of progression to Stage 3b (insulin requirement). Adapted from Insel et al. ¹ and Ziegler et al. ³

Changing patterns of risk factors and the identification of type 1 diabetes have impacted the incidence and prevalence over time, while new knowledge regarding screening, subtypes, and management of type 1 diabetes informs continuous efforts to prevent and treat type 1 diabetes with the ultimate hope of a cure.

2. PREVALENCE OF TYPE 1 DIABETES

Global prevalence of type 1 diabetes has been estimated to be 9.2 million people in 2024, with 1.8 million children under 20 years living with type 1 diabetes worldwide. ⁴ There have been many reports on the increasing prevalence of type 1 diabetes globally. A number of factors can impact prevalence and need to be examined to understand the increasing burden of type 1 diabetes, including annual incidence rates, data sources from different regions and changing mortality of type 1 diabetes. A study that also used modelling of global incidence and mortality data to examine the ‘missing prevalence’ of type 1 diabetes identified an additional 3.7 million individuals missing due to excess mortality, meaning almost 13 million individuals are impacted by type 1 diabetes worldwide. ⁵

In addition to those with overt (Stage 3) type 1 diabetes, there is a population of individuals in the earlier, presymptomatic stages of the condition (stage 1 or 2 type 1 diabetes; Figure 1). These stages are characterized by the presence of multiple islet autoantibodies indicating the autoimmune disease is active, but in stage 1, sufficient functional beta‐cell mass remains, and individuals are normoglycaemic, and in stage 2, the autoimmune condition progresses, and individuals become dysglycaemic. Based on estimates from international screening studies in children, this group could represent 0.3% of the population, with approximately 82% of these children having stage 1, 7% with stage 2 and 11% with undiagnosed Stage 3. ³ (Figure 1).

3. INCIDENCE OF TYPE 1 DIABETES

In 2024, the 10th Edition of the International Diabetes Federation (IDF) Atlas reported there were 503 000 new cases of type 1 diabetes diagnosed globally. ⁴ The annual incidence of type 1 diabetes has increased globally in the last few decades. ⁶ , ⁷ , ⁸ , ⁹ , ¹⁰ , ¹¹ , ¹² A Global Burden of Disease study reported an overall reported 0.3% annual increase in incidence of type 1 diabetes cases from 1990 to 2017. ¹³

3.1. Incidence of Type 1 Diabetes: By Age

In 2024 there were 219 000 children and adolescents (<20 years of age) diagnosed with type 1 diabetes globally, and 284 000 (56.5%) were diagnosed in adulthood. ⁴ It is unclear whether type 1 diabetes diagnosed in adulthood is increasing over time; however, diagnosis of type 1 diabetes in children, adolescents, and young people has reportedly increased from 1.5% to 3.4% per year over the past 30 years. ⁸ , ¹⁴ , ¹⁵

National, population‐based prospective studies provide the best data on the incidence of type 1 diabetes, particularly if high ascertainment rates are maintained, ¹⁰ but many of these registries were introduced for the surveillance of type 1 diabetes in childhood and adolescence. As such, there is a paucity of data on the incidence of type 1 diabetes during adulthood. ¹⁶ Annual incident cases range from 5 to 50 per 100 000 adolescents aged up to 20 years, ¹⁰ with an average of 14 per 100 000 annually. ⁹ The age group with the highest incidence is those aged 10–14 years. ⁹ , ¹³ After the pubertal years, the incidence rate significantly drops in young women but remains relatively high in young adult males up to their late 20s. ¹²

A systematic review of adult‐onset type 1 diabetes reported that there was no evidence that the incidence of type 1 diabetes increased or decreased with age in adulthood. ¹⁶ However, data from the UK Biobank show that approximately 58% of cases identified by age 60 years were diagnosed by age 30 years and almost 80% by age 40 years ¹⁷ (Figure 2). Although incidence peaks in childhood, the incidence of type 1 diabetes onset in older adults remains substantial, with incidence rates in high‐income countries ranging from 5 to 17 per 100 000 in 20–39‐year‐olds. ⁷ In adults, there may be varying approaches to defining and assessing type 1 diabetes, and as the prevalence of type 2 diabetes is much higher in adulthood, type 1 diabetes may be underreported and treated as type 2 diabetes. ¹⁶

FIGURE 2.

Proportion of new type 1 diabetes cases by age group. Adapted from Thomas et al. ¹⁷

3.2. Incidence of Type 1 Diabetes: By Region

Incidence of type 1 diabetes varies markedly across regions worldwide. ⁶ High‐income countries consistently report higher incidence rates compared to middle‐ and low‐income countries ¹³ (Figure 3); however, data on the incidence of type 1 diabetes in adult populations is lacking in low‐ and middle‐income countries. The highest annual incidence rates are reported in European countries or in populations of European origin (e.g., the USA, Canada, Australia, and New Zealand) but these countries also have the most complete and reliable data. ¹² The highest incidence rates (>30 per 100 000) were seen in Nordic countries, with Finland consistently reporting the highest incidence rates of type 1 diabetes. One possible explanation for an increased rate of type 1 diabetes in Scandinavian countries is the distance from the equator and possible low UV and vitamin D deficiency, which has been associated with the development of type 1 diabetes. ¹⁸ Interestingly, Sardinia has recently reported incidence rates of over 70 per 100 000 for children aged 0–14 years. ¹⁹ Sardinia has a very active network of paediatric diabetology clinics involved in the collection of data that may explain the high number of reported cases. ¹⁹

FIGURE 3.

Annual incidence of type 1 diabetes amongst children and adolescents aged 0–19 years by region. Source: Data from tab. 1: *Ogle et al. ⁶ and fig. 1: Hormazábal‐Aguayo et al. ⁹ IDF, International Diabetes Federation.

Following Nordic and high‐income American and Asian Pacific countries, several countries in the Middle East and North Africa also reported high incidence rates for children and adolescents ⁶ (Figure 3). Middle‐ and low‐income countries reported much lower incidence rates (Figure 3), with incidence rates for those under 20 years of age less than 5 per 100 000 for some Latin American, Sub‐Saharan African and South Asian countries. ⁹ The lack of available data and data accuracy may be a reason for the lower reported rates in these countries. ⁶ The peak age of incidence of type 1 diabetes in some Middle East and African countries is 15–19 years or later, older than in most non‐European populations (10–14 years), which may be due to missed deaths due to type 1 diabetes in younger children or possibly different phenotypes of type 1 diabetes. ⁴

Trends in the incidence of type 1 diabetes have also differed by region. For European countries with complete data from 1994 to 2021, most reported an increasing trend with incidence rates increasing from 4.9% in Romania to a 16.8% increase in Finland, while Spain and the UK both had increasing trends in the first 20 years; then incidence rates have stabilised or decreased slightly after 2013. ¹¹

In some countries, a cyclical pattern of peaks and troughs of incidence amongst children every 4–5 years has been reported. ¹⁵ , ²⁰ , ²¹ Although there has not been a clear explanation of this cyclical pattern of incidence, it has been hypothesised that it could be indicative of cycles of infectious disease. ¹⁵ During the COVID‐19 pandemic from 2020 to 2022, a systematic review found a non‐significant increase in the incidence rate from a pre‐pandemic incidence rate of 13.6 (95% CI, 7.5–24.6) to 24.8 (95% CI, 17.2–36.0) per 100000. ⁹ In England and Wales, in 2020/2021 there was a 27.4% increase in the number of boys diagnosed with type 1 diabetes and a 12.6% increase in the number of girls diagnosed. ²² However, more recent data, beyond 2022, is required to understand the true impact of COVID‐19 on incidence rates.

Changes to the reporting and data collection may impact the incidence of type 1 diabetes that has been reported globally. There may have been lower incidence rates reported during the earlier years due to an underreporting of type 1 diabetes cases ¹¹ or improvements in the screening, diagnosis, and notification of type 1 diabetes cases to national registers due to improved surveillance programmes. The 2025 International Diabetes Federation (IDF) Atlas 11th Edition reported that incidence data for type 1 diabetes in childhood and adolescence were only available for 83 countries and extrapolated for 119 countries. ⁴ In the previous IDF Atlas (10th Edition), a large increase in the incidence of type 1 diabetes in Africa and the Middle East was observed due to new data in a number of countries, which then impacted the extrapolated estimates for other countries. ⁶ Figure 3 shows the incidence rates reported by region from the IDF Atlas (10th Edition) and also shows pooled estimates of incidence rates from published studies. The incidence rate for children aged up to 20 years in North Africa and the Middle East reported by the IDF Atlas (24.4 per 100 000) is much higher than that reported in the systematic review (16.7 per 100 000), which is based on published data from 7 countries without extrapolation for countries with missing data. Although methods of data collection are one driver of higher reported incidence rates, there are a number of risk factors for type 1 diabetes that may have changed over time, driving an increase in cases. ²³ , ²⁴

4. RISK FACTORS FOR TYPE 1 DIABETES

4.1. Risk of Type 1 Diabetes: By Genetics

Genetics accounts for ~50% of the risk of type 1 diabetes, at least in children. The concordance is ~40% in monozygotic twins and ~8% in dizygotic twins. ²⁵ Having a first‐degree family member with type 1 diabetes increases the risk of developing the condition by 15‐fold; however, only ~10%–15% of individuals have a family history of type 1 diabetes at the time of diagnosis. ²⁶ The risk is twice as high if the father has type 1 diabetes compared to the mother. ²⁷

Genetic risk can also be evaluated in the general population using polygenic risk scores, that is a weighted sum of the risk associated with multiple genetic variants. Bonafacio et al. ²⁸ showed that a polygenic risk score for type 1 diabetes in the top 1% of the general population was equivalent to a 10% risk of multiple antibodies by 6 years of age. Using a different polygenic risk score, Sharp et al. showed that a lower threshold (~top 10% of the general population) could identify 78% of future cases of Stage 3 type 1 diabetes by 15 years of age, with a risk of 2.4%. ²⁹

4.2. Risk of Type 1 Diabetes Progression: By Age

The risk of developing type 1 diabetes is age‐dependent, with seroconversion and Stage 3 onset occurring more frequently in younger populations (Figure 2).

Seroconversion and development of stage 1 and 2 type 1 diabetes first peaks around 9 months to two years of age, ³⁰ , ³¹ with a median age of seroconversion of 2.1 years (IQR 1.3–4.1 years), though this is slightly older in children in the US (3.1 years) vs. Finland and Germany (2.0 and 2.1 years, respectively). ³⁰ For children in stages 1 and 2, 44% and 70% of children will progress to Stage 3 type 1 diabetes within 10 years. ³⁰ Younger age at seroconversion is associated with a faster progression to Stage 3, with children <3 years of age progressing faster than their older counterparts (hazard ratio [HR], 1.65 [95% CI, 1.30–2.09; p < 0.001]; 10‐year risk, 74.9% [95% CI, 69.7%–80.1%]) vs. children 3 years or older (60.9% [95% CI, 51.5%–70.3%]). ³⁰ Similarly, dysglycaemia at a younger age is associated with Stage 3 type 1 diabetes, with children under 13 years of age with incident dysglycaemia being at a greater risk than children 13 years and older. ³²

Stage 3 type 1 diabetes subsequently peaks in two distinct age groups in childhood: early childhood, typically between 4 and 7 years of age, and adolescence, around 10 to 14 years ⁹ , ³³ , ³⁴ There is more extensive and clearer evidence on childhood‐onset cases, where the diagnosis is generally more distinct and type 1 diabetes is proportionally the most common form of diabetes (~75% of cases). ¹⁷ These two age groups reflect the type 1 diabetes endotypes recently proposed by Leete et al. which segregate type 1 diabetes into subtypes according to age at diagnosis. ³⁵ There is debate whether they should be named phenotypes rather than endotypes ³⁶ as endotypes should refer to an underlying biological mechanism. However, the endotypes have been proposed based on age at onset and other factors, including immune system regulation, rate of β‐cell destruction, autoantibodies, body weight, genetics, and the exposome that are recognized to play a role in the development of the condition. ³⁷ Type 1 diabetes endotype 1 includes patients diagnosed before the age of 7 years (i.e., pre‐pubertal) and those older than 12 are classified as type 1 diabetes endotype 2 (i.e., pubertal) and have now been expanded to include endotypes 3–5 (young adult, adult and senior). ³⁷ Endotype 1 (onset <7 years) involves a more aggressive immune mechanism, greater levels of inflammation within their pancreas, and beta cells are lost at a more rapid rate, indicating a more severe disease. ³⁸ Puberty significantly affects those diagnosed with type 1 diabetes during the pubertal years, as hormonal changes and physical growth during this stage lead to increased insulin resistance and impact glycaemic control. ³⁸ Research regarding these endotypes of type 1 diabetes is relatively recent, and further research is required to determine whether these heterogeneous groups can explain differences in prevalence and incidence of type 1 diabetes in childhood and adolescence.

Adults have a lower rate of progression to Stage 3 than children. ³⁹ Similarly, the incidence of Stage 3 type 1 diabetes is lower in adults than in children, with an inverse relationship between age and risk, but it can occur at any age. ¹⁷ There is a paucity of data on the natural history of adult‐onset Stage 3 type 1 diabetes, including whether individuals with adult‐onset Stage 3 type 1 diabetes seroconvert as adults or children. This is due in part to the long duration of follow‐up required to capture initial seroconversion, adults being more readily misdiagnosed as type 2 diabetes and the sharp rise in the incidence of type 2 diabetes in adulthood, whereby type 1 diabetes accounts for fewer cases of diabetes (4% of cases ¹⁷ ). ⁴⁰ Nonetheless, clinical characteristics, including sex, BMI, insulin treatment, and diabetic ketoacidosis (DKA) at diagnosis, do not appear to differ between those diagnosed by 30 years of age and those diagnosed after. ¹⁷ Adults are less likely to commence insulin therapy in the first year following Stage 3 diagnosis than children, likely reflecting the rates of misdiagnosis. ¹⁷

4.3. Risk of Type 1 Diabetes: By Gender

Some data on the risk of type 1 diabetes by gender suggests the risk differs depending on the background prevalence of the condition, ¹⁴ , ⁴¹ however, differences are generally small, frequently inconsistent between and within regions ³ , ³⁰ , ⁴² , ⁴³ and there may be other variables that explain differences, such as age and/or data reliability.

4.4. Risk of Type 1 Diabetes: By Ethnicity

In addition to country‐specific differences in the incidence of type 1 diabetes, differences by ethnicity have also been observed within countries with sufficient ethnic diversity. White European populations are considered to be at greatest risk of type 1 diabetes compared to other ethnicities. For example, the SEARCH for Diabetes in Youth Study in the US reported the highest incidence of type 1 diabetes in non‐Hispanic white youth under 20 years of age (23.6/100000), ⁴⁴ , ⁴⁵ which corresponds with the higher incidence seen in Nordic and European nations as discussed above. They estimated the risk for non‐Hispanic White youth was approximately 1.5 times higher than for non‐Hispanic Black or Hispanic youth, 4 times higher than for Asian and Pacific Islander youth, and almost 9 times higher than for American Indian and Alaska Native youth. ⁴⁶ However, the highest annual increases in incidence were reported for these lower‐risk groups compared with non‐Hispanic Whites (2.7, 4.0, 4.4 vs. 0.7%/year). ⁴⁷ Similar trends are seen in Pacific Island populations, with Māori and Pasifika populations in New Zealand showing greater increases in incidence compared with Europeans in New Zealand (4.4% and 3.7% vs. 2.7%, respectively), despite their lower absolute incidence. ⁴⁸ This may be due, at least in part, to improvements in diagnosis between type 1 and type 2 diabetes.

The risk of type 1 diabetes by ethnicity is also influenced by immigration, whereby subsequent generations have a risk closer to their host country than their parent country, highlighting the likely role of environmental factors in modulating risk. For example, in Sweden, children born to mothers who had immigrated to Sweden from Asia, Europe (except Northern Europe), Latin America and North America had a lower risk of type 1 diabetes compared to both their children (second‐generation immigrants) and native‐born Swedes ⁴⁹ , ⁵⁰ , ⁵¹ and, within generations, the child's risk increased the longer the mother had resided in Sweden. ⁵² However, the risk of type 1 diabetes was increased amongst children of immigrants from Eastern Africa compared to native‐born Swedes. ⁴⁹

4.5. Risk of Type 1 Diabetes: By Socio‐Economic Status and Remoteness

The influence of socio‐economic status (SES) and remoteness or population density on the risk of type 1 diabetes is inconclusive. Several studies have reported higher rates of type 1 diabetes in higher SES and/or urban communities vs. the lower SES and/or regional/remote communities, whereas others have reported the opposite. For example, one study in Australia reported that urban and most advantaged communities were at greater risk of type 1 diabetes, with their effect being independent. ⁵³ However, in contrast, two studies in Germany between 1996 and 2014 both showed greater risk amongst children in socially deprived and less populated areas. ⁵⁴ , ⁵⁵ In Scotland, rates of type 1 diabetes were lowest amongst children in deprived urban communities. ⁵⁶

4.6. Risk: By Potential Environmental Exposures

Epidemiological studies have identified a number of environmental exposures that potentially interact with genetics to drive the development of type 1 diabetes, including viral, bacterial, and nutritional factors. Most factors are associated with early life exposure, and some factors may act as a trigger for autoimmunity, while others act as an accelerator for progression from the early stage to the symptomatic Stage 3 type 1 diabetes. For example, birth by caesarean section was associated with an increased risk of developing Stage 3 type 1 diabetes in childhood but is associated with accelerated progression rather than development of autoimmunity (i.e., early‐stage type 1 diabetes). ⁵⁷ , ⁵⁸ , ⁵⁹ The evidence for breastfeeding is inconclusive, with some studies suggesting breastfeeding reduces the risk, while others have found no association. ⁶⁰ , ⁶¹ , ⁶² Both factors have been linked to the ‘hygiene hypothesis’, that is, the theory that improved hygiene and reduced exposure to environmental pathogens (including through vaginal canal or breastfeeding) increases the risk of immune conditions, including type 1 diabetes. ⁶³ Along with nutrition and probiotics, ⁶⁴ they have also been linked to changes in the gut microbiome and the ‘leaky gut’ hypothesis. ⁶⁵ , ⁶⁶ , ⁶⁷

Viruses have also been linked with the development and acceleration of type 1 diabetes, most notably enteroviruses and especially when occurring in early childhood. ⁶⁸ , ⁶⁹ Epidemiological studies have also linked COVID‐19 with type 1 diabetes, with an increased incidence seen in children in some developed countries. ³⁴ , ⁷⁰ , ⁷¹ However, given that the progression of type 1 diabetes can take months or years from seroconversion, COVID‐19 may be an accelerator/exacerbator of preclinical type 1 diabetes, rather than a trigger of autoimmunity.

5. CHANGES IN MANAGEMENT AND COMPLICATIONS OF TYPE 1 DIABETES

Type 1 diabetes is difficult to manage, requiring a balance of diet, insulin intake, and glycaemic control. Poor management increases the risk of complications, including acute complications such as hypoglycaemia and diabetic ketoacidosis (DKA), and longer‐term microvascular complications. ⁷²

Over the last 30 years the management of type 1 diabetes has changed tremendously. The publication of the seminal diabetes control and complications trial (DCCT) in the mid‐1990s demonstrated that intensive treatment, which aimed to achieve blood glucose levels as close to the nondiabetic range as safely possible reduced early‐stage complications by 35%–76%. ⁷³ More recently, there has been rapid technological development and increased availability of numerous different devices, including continuous glucose monitoring (CGM), continuous subcutaneous insulin infusions (CSII), also known as ‘insulin pumps’, and the combination of the two to provide automated insulin delivery via a hybrid closed‐loop system, which is now recommended for people whose diabetes is not currently controlled. ⁷⁴

5.1. Acute Complications: Hypoglycaemia

Hypoglycaemia is often the result of too much insulin, exercise, or missed/delayed meals, and if left untreated can lead to seizures and a loss of consciousness. During DCCT, the intensive treatment led to increased rates of severe hypoglycaemia. At a nine‐years follow‐up, 47% of the intensive group had a severe hypoglycaemic event that included a coma or seizure compared to 25% of the conventional group, with adolescents having a significantly higher rate of hypoglycaemia than adults. ⁷⁵

Severe hypoglycaemic events can be traumatic and also lead to a fear of hypoglycaemia. Fear of hypoglycaemia is present in up to 30% of adults with type 1 diabetes, ⁷⁶ and is associated with lower quality of life, more psychological stress, and poor diabetes management. ⁷⁷ Studies have shown that CGM users have less hypoglycaemia compared to non‐CGM cohorts, and CGM also alleviates the fear of hypoglycaemia. ⁷⁷ Hybrid closed‐loop therapy has been shown to reduce the risk of hypoglycaemic coma. ⁷⁸

5.2. Diabetic Ketoacidosis (DKA)

DKA is a life‐threatening complication of type 1 diabetes, resulting from insufficient insulin, hyperglycaemia and the resulting excess production of acidic ketones, and requires emergency medical care, often with admission to intensive care. About 20%–40% of paediatric cases of type 1 diabetes initially present with DKA. ⁷⁹ , ⁸⁰ with a global average of 29.2%. ⁸¹ This rate of DKA at diagnosis increased to 39.4% in 2020 and 38.9% in 2021 during the COVID‐19 pandemic. ⁸² There is variation between countries in the proportion of those with DKA at diagnosis, with a recent systematic review identifying that DKA at diagnosis was highest in those countries with the lowest incidence of type 1 diabetes and the lowest Human Development Index, a measurement of life expectancy, education and national income. ⁸¹

Age at diagnosis is a significant factor associated with DKA at diagnosis, particularly for those diagnosed with type 1 diabetes aged less than 2 years. ⁸³ However, adolescents aged 5–14 years also had increased rates of DKA at diagnosis compared to those older than 15 years. ⁸⁰ Other factors associated with DKA at diagnosis include belonging to an ethnic minority or having a delayed diagnosis of type 1 diabetes. ⁸³

Following the onset of type 1 diabetes, DKA rates for children and adolescents with type 1 diabetes range from 2% to –8% per year, ⁷⁹ , ⁸⁴ and 5% per year in adults. ⁸⁵ DKA rates are highest in adolescents aged 10–19 years. ⁸⁵ Another factor associated with hospital admission for DKA is a previous DKA episode, with one study indicating 60% of DKA episodes occurred in 5% of children. ⁸⁴ DKA at diagnosis is associated with higher blood glucose and insulin requirements two years after diagnosis, both of which directly impact long‐term complications. ⁸⁶ As such, avoidance of an initial DKA episode can potentially lower the risk of DKA in the future. The use of CGM has been shown to lower rates of DKA ⁸⁷ ; however, studies of hybrid closed‐loop systems have shown higher ketoacidosis risk, ⁷⁸ which may be related to insufficient insulin delivery due to technical issues but requires further research.

5.3. Microvascular Complications

Uncontrolled hyperglycaemia over time can lead to microvascular complications including complications of the eyes, kidneys and nerves, the most common microvascular complication being diabetic retinopathy. The development of retinopathy is related to glycaemic control, duration of diabetes and age of onset. ⁸⁸ The changing face of the management of type 1 diabetes, beginning with stricter glycaemic targets in the 1990s and the more recent increased use of CGM and CSII technologies, means there are few studies examining longer‐term complications in a contemporary setting.

The observational follow‐up study of DCCT, the Epidemiology of Diabetes Interventions and Complications (EDIC), found that after 30 years, 33.4% of the cohort had proliferative diabetic retinopathy, 14.1% had a reduced estimated glomerular filtration rate, which can indicate kidney disease, and 3.2% had a lower extremity amputation, which can occur following diabetic peripheral neuropathy. ⁸⁹ DCCT/EDIC demonstrated that the earlier better glycaemic control is achieved after diagnosis, the lower the risk of long‐term microvascular, ⁹⁰ now further studies are required to examine these longer‐term outcomes following the use of new technologies.

Age of diagnosis has been shown to impact microvascular complications; however, the relationship between diagnosis at different ages in childhood and complications is not clear. Diagnosis of type 1 diabetes as a young child is associated with a higher risk of retinopathy, ⁸⁸ but a lower risk of developing kidney complications in adulthood. ⁹¹ , ⁹² The risk of long‐term complications for childhood‐onset type 1 diabetes may be impacted by age of diagnosis relative to puberty onset, with increased years prior to puberty delaying the onset of complications, ⁹³ but in the long term, this initial advantage may disappear. ⁷²

DCCT found that after adjustment for age of onset, duration of diabetes, and glycemia, the incidence of complications was still not completely explained. ⁸⁹ There are many other factors that will impact type 1 diabetes management and the development of complications including lifestyle changes ⁹¹ and screening. ⁷²

6. MORTALITY

People with type 1 diabetes have an increased risk of all‐cause mortality, with age‐standardised mortality rates reported from 2 to 5 times that of people without diabetes. ⁹⁴ Mortality rates for people with type 1 diabetes have decreased over the last two decades by approximately 2.1% per year in Australia and up to 5.8% per year in Denmark, possibly due to advances in treatment. ⁹⁴

Absolute mortality rates in people with type 1 diabetes increase with increasing age; however, the excess mortality relative to those without diabetes is highest for children and adolescents. Although deaths in younger individuals with type 1 diabetes are rare, they have a mortality rate up to 8.5 times that of younger people without type 1 diabetes, ⁹⁵ and are predominantly caused by acute complications. ⁹⁶ Type 1 diabetes mortality rates differ significantly between countries, with an inverse association between mortality and a country's expenditure on health. ⁹⁵

It has been reported that the age of type 1 diabetes onset impacts mortality rates. A study by Rawshani et al. found that, compared to matched controls, those diagnosed with type 1 diabetes before age 10 had the highest risk of dying in adulthood compared to those diagnosed with type 1 diabetes from 10 to 30 years of age. ⁹⁷ However, the appropriate methodology for adjustment of the duration of diabetes within this study has been questioned, ⁹⁸ and other studies have shown conflicting results. ⁹⁷ , ⁹⁹ , ¹⁰⁰ Although there are inconsistent results regarding the age of type 1 diabetes diagnosis and mortality, based on current evidence, if it is possible to delay the onset of type 1 diabetes, this would be advisable. ¹⁰¹

7. FUTURE DIRECTIONS

There are a number of research gaps when examining the global trends, prevalence, and outcomes of type 1 diabetes. The paucity of data regarding incidence and early mortality from low‐ and middle‐income countries means that a true picture of the global burden is not available.

There is also a lack of real‐world information about the incidence and prevalence of the early stages of type 1 diabetes and the patterns of progression to Stage 3 around the world. As screening becomes more widespread, this data will become increasingly available, especially with coding for early‐stage type 1 diabetes introduced in the US (International Classification of Diseases, ICD‐10‐CM: E10.A0, A1 and A2) and the UK (Systematized Nomenclature of Medicine, SNOMED; Code: 1290118005) in 2024. Consequently, the patterns of disease, including risk of progression, age of Stage 3 onset, and risk of complications, are set to change rapidly in the coming years with the introduction and uptake of disease‐modifying therapies. The first therapy, teplizumab, was approved for clinical use in stage 2 type 1 diabetes in 2022 to delay progression to Stage 3. ¹⁰²

It will also be important to better understand the incidence and prevalence of adult‐onset type 1 diabetes, including the natural history from seroconversion to the development of Stage 3, to completely appreciate the patterns of disease across the life course.

Another major gap in the epidemiology of type 1 diabetes is the lack of research examining longer‐term outcomes, particularly following the use of CGM, CSII, and hybrid closed‐loop technology and grouped by newly proposed endotypes. Part of the issue is a shorter follow‐up time of 10–20 years since the introduction of new management techniques; however, with the increasingly widespread use of these technologies, population‐based data should be available for analysis via data linkage. There are many advantages to using linked administrative data to identify long‐term outcomes compared to other traditional outcome collection methods such as patient interviews or medical record review. As administrative data is collected for other purposes, in jurisdictions where these data sources are readily available, data linkage may be a cost‐ and time‐efficient method of outcome collection. Data linkage minimizes loss to follow‐up as patients, particularly for long‐term outcomes where individuals have moved and cannot be contacted ¹⁰³ and reduces the burden of being involved in research studies on children and families.

8. CONCLUSION

The global prevalence of type 1 diabetes is increasing, particularly amongst children and adolescents. People with type 1 diabetes have increased mortality and morbidity compared to people without the condition, even with improvements in management. Age at diagnosis and duration of diabetes are important factors in the development of complications; as such, if the age of onset could be delayed, there is the potential to improve outcomes for this group. Collectively, understanding the incidence and patterns of disease is crucial for local health service planning as well as providing valuable, population‐specific insights to enhance the prediction, prevention, and treatment of type 1 diabetes.

AUTHOR CONTRIBUTIONS

KJB and SJL reviewed the literature and drafted and critically reviewed the manuscript.

FUNDING INFORMATION

KJB is supported by an NHMRC Emerging Research Leader Fellowship (GNT2033799). No other funding was utilised.

CONFLICT OF INTEREST STATEMENT

KJB is the principal investigator on the Australian Type 1 Diabetes National Screening Pilot and has previously received consultancy fees from Sanofi Aventis. SJL has no conflicts of interest to declare.

PEER REVIEW

The peer review history for this article is available at https://www.webofscience.com/api/gateway/wos/peer‐review/10.1111/dom.16501.

Bell KJ, Lain SJ. The Changing Epidemiology of Type 1 Diabetes: A Global Perspective. Diabetes Obes Metab. 2025;27(Suppl. 6):3‐14. doi: 10.1111/dom.16501

DATA AVAILABILITY STATEMENT

Not relevant to review article.