I’m a T1. American Indian and German on one side, British Isles on the other side.
According to Joslin, (http://www.joslin.org/info/genetics_and_diabetes.html), Here’s a sampling of what Dr. Warram, a Lecturer in Epidemiology at Harvard School of Public Health, said is known about the risk for TYPE 1 Diabetes:
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If an immediate relative (parent, brother, sister, son or daughter) has type 1 diabetes, one’s risk of developing type 1 diabetes is 10 to 20 times the risk of the general population; your risk can go from 1 in 100 to roughly 1 in 10 or possibly higher, depending on which family member has the diabetes and when they developed it.
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If one child in a family has type 1 diabetes, their siblings have about a 1 in 10 risk of developing it by age 50.
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The risk for a child of a parent with type 1 diabetes is lower if it is the mother — rather than the father — who has diabetes. “If the father has it, the risk is about 1 in 10 (10 percent) that his child will develop type 1 diabetes — the same as the risk to a sibling of an affected child,” Dr. Warram says. On the other hand, if the mother has type 1 diabetes and is age 25 or younger when the child is born, the risk is reduced to 1 in 25 (4 percent) and if the mother is over age 25, the risk drops to 1 in 100 — virtually the same as the average American.
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If one of the parents developed type 1 diabetes before age 11, their child’s risk of developing type 1 diabetes is somewhat higher than these figures and lower if the parent was diagnosed after their 11th birthday.
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About 1 in 7 people with type 1 has a condition known as type 2 polyglandular autoimmune syndrome. In addition to type 1 diabetes, these people have thyroid disease, malfunctioning adrenal glands and sometimes other immune disorders. For those with this syndrome, the child’s risk of having the syndrome, including type 1 diabetes, is 1 in 2, according to the American Diabetes Association (ADA).
Caucasians (whites) have a higher risk of type 1 diabetes than any other race. Whether this is due to differences in environment or genes is unclear. Even among whites, most people who are susceptible do not develop diabetes. Therefore, scientists are studying what environmental factors may be at work. Genes influencing the function of the immune system are the most closely linked to type 1 diabetes susceptibility, regardless of race. One of those genes is HLA-DR. Most Caucasians with diabetes carry alleles (gene variants) 3 and/or 4 of the HLA-DR gene. The HLA-DR7 allele plays a role in diabetes in blacks, while HLA-DR9 allele is important in diabetes among Japanese.
Among Caucasians, diabetes risk varies geographically. In general, the risk is higher in Northern Europeans than Southern Europeans. While climate may contribute to this, the fact that Sardinia in the Mediterranean also has a high risk goes against this theory. Generally the number of new cases over time fluctuates up and down, making it difficult to find an overall pattern. In recent decades, there has been an increase in type 1 diabetes in the United States and Europe. While Asians generally have a much lower incidence of type 1 diabetes, Japan is also experiencing an increasing incidence. “The gene pool doesn’t change much within one generation, so there must be an environmental or behavioral factor involved,” Dr. Warram says.
Temporal clusters of type 1 diabetes cases (i.e. those that occur around the same time — whether within families, a school or a geographical region), prompt people to suspect an environmental agent. However, no consistent explanation has come up for these clusters, and it is impossible to rule out the possibility of just coincidence. Given the fact that the development of diabetes takes many years in most cases, a clustering in time seems more likely due to chance than a common cause, Dr. Warram says. “From what we know, the autoimmune process leading to the destruction of insulin-producing beta cells in the pancreas is quite long. People can have antibodies signaling damage to the beta cells for many years without developing diabetes,” Dr. Warram says. (For information about a study to identify who is at risk for type 1 diabetes and to see if this destruction can be slowed or prevented.
Take the “outbreak” at the grade school mentioned above. Chances are, the youngsters were not attending the same school or even living in the same neighborhood when the lengthy autoimmune process leading to diabetes began. (In that process, the body’s disease-fighting immune system malfunctions, turning against the body’s own tissues and destroying them.) While we can’t be certain, it seems unlikely that we could observe a particular exposure that caused the youngsters to develop diabetes at the same time," Dr. Warram says. “Most likely it’s a matter of chance. While it is not comforting to say rare events can happen by chance, rare events are happening all the time within a given population and the chances of them occurring in one place — like a school — is high.”
Trauma as a Trigger
Some people have questioned whether a body trauma, like a car crash, or a viral infection like mumps, could trigger the onset of type 1 diabetes. Such events increase the body’s insulin requirement and strain the insulin production system if it is being destroyed by a malfunctioning immune system. “As the demands on the body increase, it can tip the body’s insulin production system over the edge,” Dr. Warram says. But the trauma itself did not “cause” the diabetes, he says.
Much has been said about a possible link between Coxsackie virus, which causes human diseases such as meningitis, and the triggering of type 1 diabetes. “You can’t dismiss the fact that sometimes the virus has been present, but its connection with the diabetes is unclear,” Dr. Warram says. Scientists do have some significant evidence that mumps does not trigger diabetes, however. A Maryland study showed that despite a great decline in mumps cases after the mumps vaccine was introduced 30 years ago, the incidence of type 1 diabetes did not change.
Some scientists believe early diet may have a role. Prolonged breastfeeding is less common in children who developed type 1 diabetes. While some studies have pointed to exposure to cow’s milk, Dr. Warram says much remains to be learned before we can assess the importance of this mechanism. To be prudent, mothers of infants at high risk of developing diabetes may want to breastfeed as long as possible and rely on cow’s milk only in moderation after the baby is weaned.
What does this mean? Not much, I’m afraid. Until there is a proven way to prevent autoimmune-mediated type 1 diabetes from occurring, knowing the genetics behind it is little more an exercise in useless data gathering (not that they shouldn’t know it, but what use is the information without a reliable intervention?).
Thank you Scott for this great post.
I think the statement about the increasing incidence of T1 is worth to discuss. I think that many couples decided against having children if one of the partners had T1 diabetes. Gladly this changed much in the last 15 years. Thus the numbers have to rise now since there is a likelyhood that T1 will be passed to the child - as you have stated in detail. So the rise is more a result of the quality of todays treatments and the confidence this created in couples to become parents. The rise in T1 incidences is still a reality of course but it has this positive side note to me.
When I was diagnosed I was told it was mostly Jewish community who got Diabetes. I don’t know why maybe at that time it occurred more often in the Jewish community…or maybe it was the consensus of doctors at that hospital.
Interesting Nel because I never liked milk…umm very interesting. Oh forgot to say I also have Osteo it was discovered in my 50s.
I am pretty sure both the race/genetic make up and the environmental factors play roles. It is just how one triggers the other, and we simply have not had enough samples and/or study interests to further investigate the issue.
And here’s why I believe that way.
My 7yo son has both T1D and Pervasive Developmental Disorder (let’s call it a cousin of autism) and is Chinese/Japanese where “annual occurrance” of T1D is said to be somewhere between 1 in 100,000~200,000 ONLY. Of course we felt like we hit the biggest lotto in the world.
While trying to find a possible link between the two, we’ve found this information online. It is a Finnish study:
Type 1 Diabetes and Autism: Is there a link?
http://care.diabetesjournals.org/content/29/2/484.full
Also, I have heard that there is a possible link between autism and diabetes at mitochondria DNA level, and it is more likely so with Type 2 diabetes than Type 1. I have not seen the source, yet.
Plus, I have noticed the increase in T1D cases in Japan through Japanese SNS in recent years among young children. But it is interesting to see how many Japanese with T1D were Dx’d in their 20s, 30s…compared to here in the States.
Oh and Irish like 1/4. Don’t forget the Irish in there!