Diabetes among young populations has become a critical global public health issue, with rising incidence and prevalence of both type 1 and type 2 diabetes mellitus (T1DM and T2DM). Historically, T1DM predominated in children, but recent data have shown a rapid rise in T2DM among adolescents and young adults.12 In the U.S., the SEARCH study (2002–2018) reported annual increases of 2.0% for T1DM (age 0–19) and 5.3% for T2DM (age 10–19).1 Similarly, the Global Burden of Disease Study showed T1DM incidence among individuals aged 10–24 rose from 7.8 to 11.1 per 100,000 between 1990 and 2019, with increases likely driven by improved diagnostics, economic development, and lifestyle changes, particularly in middle-income countries.3

In South Korea, T1DM and T2DM incidence has also risen significantly over the past two decades. Nationwide Health Insurance Review and Assessment (HIRA) data showed a 3–4% annual increase in T1DM among those aged 0–14 from 2007 to 2017, and the Korean National Health Insurance Service (NHIS) data reported a 5.6% annual increase among Korean children and adolescents from 1995 to 2014.45 The prevalence of T2DM in individuals under 30 increased over 4.4-fold between 2002 and 2016, with sharp rises among adolescents aged 10–19 years from low-income families.6 This trend reflects global patterns linked to increasing obesity, unhealthy diet, and physical inactivity.2 Importantly, young-onset T2DM is associated with more aggressive progression and greater complication risk than late-onset T2DM.2

While prevalence reflects overall disease burden, the incidence provides insight into emerging risk patterns and etiological shifts. Monitoring the incidence is essential for guiding prevention strategies, especially during adolescence and young adulthood—a key transitional period for health behaviors and care access. However, previous studies on diabetes trends in young Korean populations have been limited by narrow age scopes, outdated datasets, and insufficient coverage of T2DM incidence. Moreover, despite growing awareness of the influence of socioeconomic determinants on diabetes risk, few comprehensive studies have simultaneously evaluated both T1DM and T2DM across diverse age groups and socioeconomic strata. To address these gaps, we aimed to investigate recent trends in the incidence and prevalence of T1DM and T2DM among Korean children, adolescents, and young adults, with a particular focus on socioeconomic disparities in diabetes risk.

This cohort study identified a significant increase in both T1DM and T2DM incidence and prevalence among young Koreans between 2008 and 2021. T1DM incidence rose steadily, particularly in females and children aged 0–14 years, while its prevalence more than doubled across all age groups. In contrast, T2DM incidence increased more sharply, by 8.3% annually, particularly in males and adolescents aged 13–18 years. T2DM prevalence nearly quadrupled, driven by increases in both the 13–18 and 19–29 age groups. Individuals with low SES exhibited a significantly higher risk, especially for T2DM.

Globally, T1DM incidence among adolescents and young adults (10–24 years) increased between 1990 and 2019, although regional differences were observed.3 While some western countries, such as Norway, Sweden, and Canada, reported stabilization or even a slight decline in Finland, most other regions, particularly in Asia, continued to experience sustained increases.3 Although East Asian countries generally report lower T1DM incidence rates than western populations, multiple studies have documented steady upward trends. In Japan, registry-based data showed an increase in childhood-onset T1DM incidence from 1.5 to 2.25 per 100,000 between 1986 and 2010, with the highest incidence observed in the 10–14 age group.1213 In Beijing, hospitalization-based data demonstrated an increase in childhood-onset T1DM incidence from 0.88 to 2.37 per 100,000 between 1995 and 2010, with a more rapid increase among boys and children aged 0–4 years.14 Similarly, Taiwan’s national database revealed an increase from 2.63 to 3.34 per 100,000 between 1999 and 2010.15 Nationwide data in Korea demonstrate a sustained rise in childhood- and adolescent-onset T1DM.458 Our study expands upon prior East Asian findings by capturing recent trends across the full pediatric to young adult age range, confirming a continued increase and aligning with patterns seen in higher-incidence Western regions. These findings suggest a shift in the epidemiologic landscape, highlighting the need for regionally tailored public health strategies. This rising trend may be driven by immune–mediated mechanisms, including genetic susceptibility (e.g., human leukocyte antigen genotypes), impaired immune tolerance, and viral infections such as enterovirus.16 Environmental factors proposed by the hygiene hypothesis—such as reduced microbial exposure early in life—along with gut microbiota alterations and vitamin D deficiency, may further contribute to autoimmune activation in genetically predisposed individuals.16

Despite the growing recognition of T2DM as a significant public health concern among young populations, comprehensive epidemiological data remain limited. According to the International Diabetes Federation, indigenous and African-American youth had the highest incidence of T2DM in 2021 (31–94 per 100,000 per year), with the highest prevalence reported among youth in Brazil, Mexico, the United States and Canada—particularly among Indigenous and Black populations (160–3,300 per 100,000).17 Globally, an estimated 41,600 new pediatric cases of T2DM occurred in 2021, with the largest burdens in China, India, and the United States.18 Notably, the Western Pacific region accounted for nearly 30% of all cases, reflecting a substantial rise in T2DM prevalence across Asia.18 East Asian countries have also reported striking increases. In Japan, 80% of newly diagnosed pediatric diabetes cases were T2DM, with a 1.5-fold increase in incidence between 1975 and 1990, closely linked to rising obesity rates.1920 In Taiwan, a nationwide screening program (1992–1999) found that 54.2% of newly diagnosed diabetes cases in children aged 6–18 years were T2DM, with an incidence of 6.5 per 100,000.21 The sharp rise in T2DM incidence and prevalence in our study mirrors global trends.21 Age subgroup analyses revealed the greatest increase among adolescents aged 13–18 years, with prevalence nearly quadrupling—particularly in late adolescence and young adulthood. Consistent with earlier East Asian studies, our findings indicate a continued acceleration of early-onset T2DM in Korea, resembling patterns seen in Western countries. This trend is largely driven by rising adolescent obesity and sedentary behaviors, which contribute to insulin resistance, β-cell dysfunction, and hyperglycemia.22223

In this study, we observed a higher incidence and prevalence of T1DM in females compared to in males, consistent with findings from other Asian populations. A Japanese cohort study of children aged 0–14 years found a higher T1DM prevalence in females.12 Similarly, a hospital–based study in Beijing reported a female predominance of newly diagnosed T1DM cases among children aged 5–14 years.24 A nationwide Taiwanese study also reported a higher T1DM incidence in females.15 A global analysis of 76 populations showed that a female excess in T1DM was most common in low-incidence regions (88%), while male predominance was observed in high-incidence areas (68%).25 Regional variations in T1DM suggest that sex-specific patterns are shaped by genetic, environmental, and demographic factors. Higher T1DM incidence and risk burden in females may reflect stronger autoimmune reactivity, earlier puberty, and hormonal influences on immune function.26 Conversely, our study found a male predominance in T2DM, aligning with higher obesity rates among Korean males.27 Similar trends have been reported in China and Korea, while female predominance has been observed in certain ethnic groups and U.S. youth.6282930 These discrepancies likely reflect sociocultural, behavioral, and physiological factors, including pubertal insulin resistance and sex differences in fat distribution.29 Males tend to have more visceral adiposity and hepatic insulin resistance during puberty, and may be less engaged in preventive care, contributing to delayed diagnosis and greater metabolic risk.3132 Our findings underscore the importance of sex-specific prevention and management strategies in youth-onset diabetes.

Our study identified significant socioeconomic disparities in both T1DM and T2DM, with disparities being particularly pronounced in T2DM. Lower-income and ethnic minority groups experience higher incidence and poorer diabetes-related health outcomes, likely driven by multiple social determinants of health. These include food insecurity, lack of private health insurance, and limited access to healthcare services.33 Findings from the TODAY cohort and Pediatric Diabetes Consortium reported that nearly half of youth with T2DM were from low-income households, reinforcing the strong association between poverty and T2DM prevalence.3435 Several mechanisms may underlie the elevated diabetes risk in low-SES populations. Limited healthcare access can delay diagnosis and treatment, leading to under-detection and poor glycemic control.36 Low-income families often live in environments with reduced access to healthy foods and safe physical activity spaces, increasing risk of obesity and insulin resistance.3738 Food insecurity further contributes by promoting calorie-dense and nutrient-poor diets.39 Chronic psychosocial stress due to financial hardship may also disrupt neuroendocrine function, such as HPA axis dysregulation, and worsen metabolic outcomes.40 Parental education and health literacy influence youth awareness and engagement in preventive behaviors.4142 While the link between low SES and T2DM is well established, similar patterns have been reported in T1DM. The SEARCH study (2002–2015) found that 14.1% of T1DM and 43.7% of T2DM cases came from households earning < $25,000/year.43 Although mechanisms in T1DM are less defined, possible contributors include delayed diagnosis, reduced access to technologies, and early-life environmental exposures disproportionately affecting low-SES populations. These findings suggest that socioeconomic disadvantage impact both T1DM and T2DM risk, underscoring the need for further research. Collectively, these factors likely contribute to the earlier onset and worse outcomes, as demonstrated in our study and previous reports showing higher incidence and prevalence among low-income populations.635 Targeted public health strategies are urgently needed to address these social and structural inequities.

This study has several limitations. First, reliance on claims data may introduce misclassification of diabetes type. Although the National Registration Project requires physician–confirmed insulin deficiency or evidence of autoimmunity to classify T1DM cases, misclassification remains possible. To minimize errors, we included only cases where both a diagnosis and a corresponding drug prescription were recorded simultaneously. Second, the absence of anthropometric data limits our ability to assess underlying risk factors contributing to diabetes trends, particularly for T2DM, where obesity is a major determinant. Finally, although the study captures nationwide data, it may not fully account for undiagnosed diabetes cases, particularly among individuals with T2DM who do not use anti-diabetic medication. Our stringent inclusion criteria, which required documented prescriptions, may have led to an underestimation of the true burden of T2DM in this population.

In conclusion, the incidence and prevalence of both T1DM and T2DM rose significantly between 2008 and 2021. T1DM incidence exhibited a gradual annual rise, particularly among younger children, and its prevalence more than doubled across all age groups. In contrast, T2DM incidence increased more rapidly, with a disproportionate impact on males and adolescents aged 13–18 years. T2DM prevalence nearly quadrupled, driven by sharp increases in adolescents and young adults (13–29 years). Socioeconomic disparities were evident, particularly T2DM, with individuals from lower SES backgrounds at markedly higher risk. These findings underscore the urgent need for targeted public health interventions, early detection strategies, and policy measures addressing socioeconomic inequalities in order to mitigate the growing burden of young-onset diabetes in South Korea.