You and your relatives have a lot in common. Things like blue eyes, tall height, and diseases like asthma or heart disease might run in your family. If you have type 1 diabetes, you might wonder if that has also passed down your family tree to you. And you may worry that your children could get it too.
Type 1 diabetes is an autoimmune disease that happens when your immune system mistakenly attacks beta cells in your pancreas that make insulin. Genes could play a role in that immune system attack.
Type 1 diabetes does run in families. Having a parent, brother, sister, or child with type 1 diabetes makes you about 15 times more likely to get this disease than people who don't have a family history. Even so, around 85% of people who get type 1 diabetes have no other family members with the disease. And most people who do have a family history of type 1 diabetes don't ever get it themselves.
That's because genes alone don't cause diabetes. Even if you carry genes that increase your risk, something in your environment has to trigger the disease. Researchers are learning more about the genetic and environmental causes of type 1 diabetes. What they've found out could lead to new ways to prevent and treat this disease.
Genes Linked to Type 1 Diabetes
Scientists are studying gene changes called mutations that are linked to type 1 diabetes.
Many of these genes affect how your immune system works. Human leukocyte antigen (HLA) genes help your immune system tell the difference between your own cells and foreign cells like germs. A problem with your HLA genes could be one reason why your immune system mistakenly attacks cells in your pancreas that make insulin.
HLA genes are further divided into different variants called DR. They're written like this: HLA-DR1. Some of these variants, like HLA-DR2, seem to protect against type 1 diabetes. Others increase the risk.
The insulin (INS) gene is also linked to type 1 diabetes. This gene gives your body the instructions it needs to make insulin.
People of different races may have different gene variants. White people are at the highest risk of having type 1 diabetes overall. Most White people with type 1 diabetes have the gene HLA-DR3 or HLA-DR4. These genes are linked to autoimmune diseases. The gene HLA-DR7 may increase the chances of type 1 diabetes in Black people, while HLA-DR9 increases them in Japanese people.
How Family History Affects Diabetes Risk
The odds of someone without a family history getting type 1 diabetes are less than 1%. But if one or more of their relatives have the disease, those odds go up.
How big is the risk among family members? That depends on how close the relative with type 1 diabetes is. Identical twins are the closest genetic match. When one identical twin has type 1 diabetes, the other has about a 70% greater chance of also getting diabetes at some point in their life. In a brother or sister who is not a twin, the chances are is only 6% to 7% higher.
How likely a parent is to pass type 1 diabetes to their children differs by the parent's assigned gender at birth. If a mother has type 1 diabetes, her children's chances of having it are about 1% to 4% higher than normal. And if the father has type 1 diabetes, his children's likelihood is 6% to 9% higher. The difference in genetic risk between parents may be because a mother's genes become less active when they pass to her child.
Other things also increase the chance of a child having type 1 diabetes, including how old their parent was when they were diagnosed and when they gave birth. The chances that a child will inherit type 1 diabetes are:
- 1 in 25 if their mother gave birth before age 25
- 1 in 100 if their mother gave birth after age 25
- 1 in 10 to 1 in 14 if both parents have type 1 diabetes
- Double if a parent was diagnosed with type 1 diabetes before age 11
Even close family members of someone with type 1 diabetes are at low risk of getting it themselves – except for people who have type 2 polyglandular autoimmune syndrome. This inherited autoimmune disease affects 1 out of 7 people with type 1 diabetes. Each child of a person with this syndrome has a 50/50 chance of getting type 1 diabetes.
The Role of Genes and the Environment in Type 1 Diabetes
Most people who are at risk of having type 1 diabetes because of their genes don't get the disease. That's because genes only set up a person for diabetes. Experts believe that certain triggers in the environment actually cause it.
What are those triggers and how do they increase the chances of diabetes? Researchers don't know for sure, but they're trying to find out.
One possible trigger is a virus that makes the immune system go haywire and attack insulin-making cells in the pancreas. The type of diet people eat during infancy and childhood might also be involved. For example, type 1 diabetes may be more common in people who weren’t breastfed and who started solid foods at a young age.
It's possible that many triggers work together to cause this disease. Learning those exact triggers could help doctors find ways to stop type 1 diabetes.
Should My Family Get Tested for Type 1 Diabetes Risk?
Today, doctors can do a blood test to learn whether a person at risk might get type 1 diabetes years before they have any symptoms. If you or any close family members have type 1 diabetes, you may want to have your children tested to see if they're at risk.
The test measures how much of certain antibodies your child's immune system makes. Having high levels of these antibodies could raise their odds of having type 1 diabetes. If the test shows this is the case, their doctor can treat them early to delay the development of type 1 diabetes and help prevent complications.
Ask your doctor or your child's doctor if your children or other family members need type 1 diabetes risk screening. You can also get screened through TrialNet, an organization of researchers who study diabetes. If they find family members of a person with type 1 diabetes have two or more antibodies for the condition, they’ll check in on your health regularly and keep you up to date on the latest research into type 1. They may also pay for your travel and other expenses to screening tests or studies.
Show Sources
Photo Credit: DigitalVision/Getty Image
SOURCES:
A Guide to Genetics and Health: "Diseases That Run in the Family."
American Diabetes Association: "Genetics of Diabetes."
CDC: "What is Type 1 Diabetes?"
Emory University School of Medicine: "What is Type 1 Diabetes (T1D)?"
JDRF: "Causes of Type 1 Diabetes," "T1Detect: Learn About Type 1 Diabetes Risk Screening," "Who is at Risk for Type 1 Diabetes?" "Will I Pass on Type 1 Diabetes to My Baby?"
MedlinePlus: "INS Gene."
Pediatric Diabetes: "Genetics of Type 1 Diabetes."
StatPearls: "Biochemistry, HLA Antigens."
Type 1 Diabetes TrialNet: "Our Research,” “Frequently Asked Questions.”
University of California, San Francisco: "Causes of type 1 diabetes," "Genetics of Type 1a."
