What Causes Type 1 Diabetes?

What is type 1 diabetes?

Type 1 diabetes is a chronic autoimmune condition in which the body attacks its own insulin-producing cells. Insulin is a hormone produced by the pancreas that helps control the amount of glucose (sugar) in the body, allowing the body to use glucose for energy. 

In type 1 diabetes, insulin is no longer produced by the body and needs to be injected externally. The insulin injections allow glucose to enter the cells, so they no longer starve. 

Difference between type 1 and type 2 diabetes

Type 1 and type 2 diabetes are chronic conditions in which the body cannot properly regulate blood sugar levels, leading them to become too high. Treatment is available for both, but currently, no cure exists. 

In type 1 diabetes, individuals don’t produce insulin. Type 1 frequently develops in childhood and is a product of the body attacking its own insulin-producing cells. 

By contrast, type 2 diabetes generally develops in adulthood. It’s commonly caused by obesity and an inactive lifestyle. However, age and genetics are also known to play a role. In type 2, individuals don’t respond to insulin as they should. 

Type 2 diabetes can be treated with lifestyle changes, including losing weight, eating well, and exercising. Insulin therapy may also be required. 

How common is type 1 diabetes?

The overall incidence of type 1 diabetes has been increasing in recent years. Around 9 million¹ people are known to have it. This highlights that type 1 diabetes is more widely recognized and diagnosed and that environmental factors could play a larger role. 

Symptoms of type 1 diabetes

The symptoms of type 1 diabetes can initially be subtle. However, they can become quite severe and include: 

• frequent urination

• thirstiness

• fatigue

• unexplained weight loss

• increased appetite

• blurred vision

• irritability and other mood changes

What causes type 1 diabetes?

The ultimate cause of type 1 diabetes is unknown, and there are no known means of preventing it. Presently, it’s understood to be caused by a combination of a genetic predisposition and environmental triggers. 

Current research investigating these causes in more detail is underway to identify potential means of delaying the onset of diabetes. 

Genetics

The risk of type 1 diabetes is 15-fold higher for siblings of individuals with diabetes than the risk of type 1 in the general population, highlighting the involvement of genetics. In identical twins, there is a further increased risk of progression to type 1 if one twin is diagnosed.

Studies have been variable in quantifying this increased risk, with rates reported anywhere between 30% to 70%².

Over 60 loci have been found that are associated with an increased risk for type 1. 

A locus is a specific physical position on a chromosome where a particular gene is located. This means that research currently understands where these genes are located on the chromosome, and further research is continuing to determine how these genes specifically influence the risk of type 1 diabetes. 

The major histocompatibility complex is a set of genes correlated with the greatest increased risk of type 1 diabetes. 

This set of genes is part of our immune system and plays the role of recognizing “self,” i.e., our own cells, and the “nonself” cells of invasive organisms, which are generally infectious diseases. 

Understanding the role that genetics plays is highly important as it will enable researchers in the future to identify individuals with high genetic risk and to protect them from potential environmental triggers to delay the onset of the disease. 

Further genetic understanding could also assist with refining treatment for type 1 diabetes to minimize diabetes-related complications and reduce the overall disease burden. 

Exposure to viruses

Viruses, particularly human enteroviruses (HEV)³, appear to play a major role in the development of type 1 diabetes. Rotavirus, mumps virus, rubella virus, and cytomegalovirus have also all been correlated with type 1 diabetes development, though to a lesser degree. 

HEV infections are very common and generally cause mild cold-like symptoms. However, some strains are more severe and can lead to worse diseases. 

The beta cells of the pancreas have been identified as being particularly susceptible to HEV infection. This susceptibility is thought to be driven by two factors. The first is that beta cells have receptors for the virus to bind and enter.

Secondly, it is thought that beta cells have certain features that provide an optimal environment for the virus to successfully infect and replicate. 

It’s thought that in healthy individuals, this virus can be adequately controlled with a sufficient immune response. However, in individuals with a genetic predisposition to type 1 diabetes, it’s understood that their antiviral immune response may be impaired.

This means that the viral infection remains in the body for longer and has more time to reach tissues such as the pancreas.

Future research could help determine how viral exposure leads to type 1 diabetes. Additionally, developing and administering an enteroviral vaccination soon after birth could be a potential intervention. 

Environmental factors

Not all individuals with the genetic predisposition to type 1 diabetes go on to develop the condition, so it’s become evident that certain environmental conditions play a role in its cause. 

Low vitamin D⁴ has been correlated with an increased risk of type 1 diabetes, as vitamin D plays a crucial role in regulating the immune system. This could explain why diagnoses of diabetes follow a seasonal pattern — higher in months with less sunshine as the sun is required for the body to produce natural vitamin D. 

Research⁵ has found that psychological stress and stressful life events can trigger type 1 diabetes or worsen its course. Stress impacts hormones and subsequently can shift the immune response, triggering type 1 diabetes. 

For some good news, however, breastfeeding⁶ has been found to have a protective effect on the development of type 1 diabetes. 

Type 1 diabetes risk factors

As the direct cause of type 1 diabetes is yet to be fully understood, many potential causes are also understood as risk factors. This is because they are known to contribute to the development of type 1 diabetes but are not necessarily outright causes.

Race: The highest rates of type 1 diabetes are seen in Caucasians. This may be due to genetic factors.

Living far from the equator: The incidence of type 1 diabetes increases in populations more distant from the equator. For example, Finland in the far north of Europe has a prevalence of 35 per 100,000 per year⁷, while Ethiopia, close to the equator, found a prevalence of only 2.1 per 100,000 per year⁸.

Genetic predisposition: Type 1 diabetes frequently runs in families. However, having a genetic predisposition doesn’t mean the person will develop the disease.

Environmental factors: Pollution, diet, infections, and stress are closely linked to type 1 diabetes.

Who is at risk for type 1 diabetes?

Adults

Generally, type 1 diabetes is diagnosed before the age of 40. However, sometimes illnesses later in life can trigger an immune response that brings about the disease. 

Children

Age is a risk factor as type 1 diabetes usually develops in younger adults and children. 

Diagnosis and tests for type 1 diabetes

In the presence of symptoms, a doctor will check the person’s blood glucose levels to see if type 1 diabetes is present.  

The predominant screening test for type 1 diabetes is a random blood glucose test, which tells physicians how much blood glucose is circulating in an individual’s bloodstream. A fasting blood glucose test can be taken following an overnight fast. 

Another test that can be carried out is the Hb1Ac test. This measures an individual’s average blood glucose level from the previous 2–3 months, so it will be higher in individuals diagnosed with type 1 diabetes. 

A blood test can also be carried out to identify the presence of islet cell antibodies, which are a marker of type 1 diabetes. 

Complications of type 1 diabetes

Over time, particularly when blood sugar levels are poorly managed, diabetes has the potential to contribute to a wide variety of other health complications. 

Heart

After a while, high blood sugar levels can damage the vessels supplying blood to the heart. Ongoing damage can also lead the immune system to turn and attack the heart. 

Eyes

Damage to blood vessels impacts the blood supply to the eyes, causing them to become leaky or blocked. This leads to retinal damage, causing partial or complete blindness. 

Kidneys

Diabetic nephropathy is a common complication of diabetes. High blood glucose levels can lead to damage to the blood vessel clusters of the kidneys that filter waste from the blood, eventually leading to kidney damage and high blood pressure. 

Blood vessels

High blood glucose impacts the elasticity of blood vessels over time, causing them to narrow and subsequently impact blood flow. 

Nerves

Persistent high blood glucose can damage nerves, preventing messages from being sent around the body. 

Prevention and treatment

Type 1 diabetes can’t be prevented, only delayed. Future research may identify a potential means of prevention or ways to preserve remaining pancreatic cells in individuals who have been recently diagnosed. 

Although no cure for type 1 diabetes exists, the disease can be managed. Treatment involves the use of insulin injections to control blood glucose levels. The insulin can be injected into soft tissue, such as the stomach, multiple times per day. 

Alternatively, some people use insulin pumps, devices attached to the body that provide a steady input of insulin throughout the day. 

Managing type 1 diabetes

Given that no cure for type 1 diabetes exists, taking steps to minimize the burden of this condition and the potential long-term complications is important. 

It can take a while to adjust to life with diabetes, but it may get easier. By establishing a strong routine, it can become easier to make the necessary adjustments, such as: 

• regularly testing blood sugar level

• counting carbohydrates

• staying physically active

• eating healthy 

When to visit a doctor

People who experience any of the listed symptoms should visit their doctor and get their blood sugar tested. People with a sibling who has type 1 diabetes may want to test their antibodies to see if they’ll develop the disease. 

This allows them to potentially delay disease onset and have time to prepare and understand the treatment protocol. 

The lowdown

As it stands, type 1 diabetes is understood to be caused by an interplay of nonmodifiable genetic factors and modifiable environmental factors. There’s still a long way to go towards fully understanding this complex condition. 

It’s hoped that with further research, therapies and technologies can be improved to minimize the overall burden of type 1 diabetes or someday even develop a cure.