Type 1 diabetes
Type 1 diabetes (T1D), formerly known as juvenile diabetes, is an autoimmune disease that originates when cells that make insulin (beta cells) are destroyed by the immune system.[5] Insulin is a hormone required for the cells to use blood sugar for energy and it helps regulate glucose levels in the bloodstream.[6] Before treatment this results in high blood sugar levels in the body.[7] The common symptoms of this elevated blood sugar are frequent urination, increased thirst, increased hunger, weight loss, and other serious complications.[5][8] Additional symptoms may include blurry vision, tiredness, and slow wound healing.[6] Symptoms typically develop over a short period of time, often a matter of weeks if not months.[7]
Type 1 diabetes
Diabetes mellitus type 1, insulin-dependent diabetes, juvenile diabetes
Diabetic ketoacidosis, severe hypoglycemia, cardiovascular disease, damage to the eyes, kidneys, and nerves
At any age; over days to weeks
Lifelong
Body does not produce enough insulin
Family history, celiac disease, autoimmune diseases
High blood sugar levels, autoantibodies targeting insulin-producing cells.
Monitoring blood sugar, injected insulin, managing diet
10-12 years shorter life expectancy[1][2][3]
11–22 million cases globally[4]
The cause of type 1 diabetes is unknown,[5] but it is believed to involve a combination of genetic and environmental factors.[7] The underlying mechanism involves an autoimmune destruction of the insulin-producing beta cells in the pancreas.[6] Diabetes is diagnosed by testing the level of sugar or glycated hemoglobin (HbA1C) in the blood.[9][10] Type 1 diabetes can typically be distinguished from type 2 by testing for the presence of autoantibodies[9] and/or declining levels/absence of C-peptide.
There is no known way to prevent type 1 diabetes.[5] Treatment with insulin is required for survival.[7] Insulin therapy is usually given by injection just under the skin but can also be delivered by an insulin pump.[11] A diabetic diet and exercise are important parts of management.[6] If left untreated, diabetes can cause many complications.[5] Complications of relatively rapid onset include diabetic ketoacidosis and nonketotic hyperosmolar coma.[9] Long-term complications include heart disease, stroke, kidney failure, foot ulcers and damage to the eyes.[5] Furthermore, since insulin lowers blood sugar levels, complications may arise from low blood sugar if more insulin is taken than necessary.[9]
Type 1 diabetes makes up an estimated 5–10% of all diabetes cases.[12] The number of people affected globally is unknown, although it is estimated that about 80,000 children develop the disease each year.[9] Within the United States the number of people affected is estimated at one to three million.[9][13] Rates of disease vary widely, with approximately one new case per 100,000 per year in East Asia and Latin America and around 30 new cases per 100,000 per year in Scandinavia and Kuwait.[14][15] It typically begins in children and young adults but can begin at any age.[7][16]
Diagnosis[edit]
Diabetes is typically diagnosed by a blood test showing unusually high blood sugar. The World Health Organization defines diabetes as blood sugar levels at or above 7.0 mmol/L (126 mg/dL) after fasting for at least eight hours, or a glucose level at or above 11.1 mmol/L (200 mg/dL) two hours after an oral glucose tolerance test.[36] The American Diabetes Association additionally recommends a diagnosis of diabetes for anyone with symptoms of hyperglycemia and blood sugar at any time at or above 11.1 mmol/L, or glycated hemoglobin (hemoglobin A1C) levels at or above 48 mmol/mol.[37]
Once a diagnosis of diabetes is established, type 1 diabetes is distinguished from other types by a blood test for the presence of autoantibodies that target various components of the beta cell.[38] The most commonly available tests detect antibodies against glutamic acid decarboxylase, the beta cell cytoplasm, or insulin, each of which are targeted by antibodies in around 80% of type 1 diabetics.[38] Some healthcare providers also have access to tests for antibodies targeting the beta cell proteins IA-2 and ZnT8; these antibodies are present in around 58% and 80% of type 1 diabetics respectively.[38] Some also test for C-peptide, a byproduct of insulin synthesis. Very low C-peptide levels are suggestive of type 1 diabetes.[38]
Prevention[edit]
There is no way to prevent type 1 diabetes;[102] however, the development of diabetes symptoms can be delayed in some people who are at high risk of developing the disease. In 2022 the FDA approved an intravenous injection of teplizumab to delay the progression of type 1 diabetes in those older than eight who have already developed diabetes-related autoantibodies and problems with blood sugar control. In that population, the anti-CD3 monoclonal antibody teplizumab can delay the development of type 1 diabetes symptoms by around two years.[103]
In addition to anti-CD3 antibodies, several other immunosuppressive agents have been trialled with the aim of preventing beta cell destruction. Large trials of cyclosporine treatment suggested that cyclosporine could improve insulin secretion in those recently diagnosed with type 1 diabetes; however, people who stopped taking cyclosporine rapidly stopped making insulin, and cyclosporine's kidney toxicity and increased risk of cancer prevented people from using it long-term.[104] Several other immunosuppressive agents – prednisone, azathioprine, anti-thymocyte globulin, mycophenolate, and antibodies against CD20 and IL2 receptor α – have been the subject of research, but none have provided lasting protection from development of type 1 diabetes.[104] There have also been clinical trials attempting to induce immune tolerance by vaccination with insulin, GAD65, and various short peptides targeted by immune cells during type 1 diabetes; none have yet delayed or prevented development of disease.[105]
Several trials have attempted dietary interventions with the hope of reducing the autoimmunity that leads to type 1 diabetes. Trials that withheld cow's milk or gave infants formula free of bovine insulin decreased the development of β-cell-targeted antibodies, but did not prevent the development of type 1 diabetes.[106] Similarly, trials that gave high-risk individuals injected insulin, oral insulin, or nicotinamide did not prevent diabetes development.[106]
Epidemiology[edit]
Type 1 diabetes makes up an estimated 10–15% of all diabetes cases[26] or 11–22 million cases worldwide.[4] Symptoms can begin at any age, but onset is most common in children, with diagnoses slightly more common in 5 to 7 year olds, and much more common around the age of puberty.[107][18] In contrast to most autoimmune diseases, type 1 diabetes is slightly more common in males than in females.[107]
In 2006, type 1 diabetes affected 440,000 children under 14 years of age and was the primary cause of diabetes in those less than 15 years of age.[108][26]
Rates vary widely by country and region. Incidence is highest in Scandinavia, at 30–60 new cases per 100,000 children per year, intermediate in the U.S. and Southern Europe at 10–20 cases per 100,000 per year, and lowest in China, much of Asia, and South America at 1–3 cases per 100,000 per year.[30]
In the United States, type 1 and 2 diabetes affected about 208,000 youths under the age of 20 in 2015. Over 18,000 youths are diagnosed with Type 1 diabetes every year. Every year about 234,051 Americans die due to diabetes (type I or II) or diabetes-related complications, with 69,071 having it as the primary cause of death.[109]
In Australia, about one million people have been diagnosed with diabetes and of this figure 130,000 people have been diagnosed with type 1 diabetes. Australia ranks 6th-highest in the world with children under 14 years of age. Between 2000 and 2013, 31,895 new cases were established, with 2,323 in 2013, a rate of 10–13 cases per 100,00 people each year. Aboriginals and Torres Strait Islander people are less affected.[110][111]
Since the 1950s, the incidence of type 1 diabetes has been gradually increasing across the world by an average 3–4% per year.[30] The increase is more pronounced in countries that began with a lower incidence of type 1 diabetes.[30] A single 2023 study suggested a relationship between COVID-19 infection and the incidence of type 1 diabetes in children;[112] confirmatory studies have not appeared to date.