Type 1 diabetes is usually considered a disease diagnosed in childhood, but it can present at any age.1-3 In the US, about 1.5 million adults are newly diagnosed with diabetes every year with an estimated 64,000 people diagnosed with type 1 diabetes and more than 1.4 million diagnosed with type 2 diabetes.1 The majority of people are 45 years or older at diagnosis. Of the 64,000 new cases of type 1 diabetes diagnosed annually in the US, 27,000 occur in children between ages 0 to 19 years and 37,000 in adults ages 20 years and older.4
Despite the greater number of cases in adults, the actual incidence rate is much higher in children because the adult age span covers many more individuals.4 In one longitudinal study, the records of more than 61 million people were examined for the years 2001 to 2015. New diagnosis of type 1 diabetes was found in 32,476 people of which 13,302 were youths aged 0 to 19 years and 19,174 were adults aged 20 – 64 years. The incidence annually was lower in adults than youths (18.6 per 100,000 vs 34.3 per 100,000, respectively).
Since the diagnosis of type 2 diabetes is so common in adults, sometimes adults presenting with type 1 diabetes are misdiagnosed.2,5 However, a cross-sectional analysis of genetic susceptibility to type 1 diabetes found that at least 42% of type 1 diabetes occurs after age 30 years. The study found that people diagnosed with type 1 diabetes after age 30 compared to those diagnosed with type 2 diabetes had a lower BMI (27.4 vs 32.4), were more likely to have ketoacidosis (11% vs 0.3%), and were more likely to need insulin within the first year of diagnosis (89% vs 6%), respectively.5 The authors suggest that people who require insulin therapy within 3 years of diagnosis have a high likelihood of type 1 diabetes regardless of initial diagnosis.2,5 Also, they suggest that clinicians consider type 1 diabetes as a diagnosis for anyone with type 2 diabetes who has poor glycemic control despite increasing therapy, particularly if the person is not obese.
References
- National Diabetes Statistics Report. Atlanta, GA: Centers for Disease Control and Prevention, U.S. Dept of Health and Human Services; 2020.
- Thomas NJ, Lynam AL, Hill AV, et al. Type 1 diabetes defined by severe insulin deficiency occurs after 30 years of age and is commonly treated as type 2 diabetes. Diabetologia 2019; 62 (7): 1167-1172.
- Classification and diagnosis of diabetes: standards of medical care in diabetes-2020. Diabetes Care 2020; 43 (Suppl 1): S14-s31.
- Rogers MAM, Kim C, Banerjee T, et al. Fluctuations in the incidence of type 1 diabetes in the United States from 2001 to 2015: a longitudinal study. BMC Med 2017; 15 (1): 199.
- Thomas NJ, Jones SE, Weedon MN, et al. Frequency and phenotype of type 1 diabetes in the first six decades of life: a cross-sectional, genetically stratified survival analysis from UK Biobank. Lancet Diabetes Endocrinol 2018; 6 (2): 122-129.
.png)
