Dr Sarah Jarvis comments on Type 1 diabetes risk factors

All the facts in this article are supported by the medical evidence. They do not for a moment suggest that getting type 1 diabetes is ever a person, or their parent’s, fault. However, if the scientific community is ever to tackle growing problem of type 1 diabetes, it is essential that we highlight the evidence we have both to ensure that parents take what small steps they can and that research continues in the right direction to look for solutions for the future.

It is absolutely not possible to reduce your risk of getting type 1 diabetes to nothing. Nor is it possible to avoid the vast majority of viral infections. However, it is extremely important to consider the scientific facts that we do know and to use them to reduce that risk, even by a small amount, if it is at all possible. This is what I stated in my blog. The vast majority of parents who have a child affected by type 1 diabetes were themselves immune to German measles (rubella), and therefore did not put their child at risk of developing congenital rubella syndrome. However, as a doctor it is my role to ensure that all people are aware of the risks of not getting immunisations, and the fact that congenital rubella is associated with a very large increase in the risk of getting type 1 diabetes is just one of these risks.

Likewise, failing to immunise a child against mumps is likely to increase their risk of developing type 1 diabetes if they subsequently develop mumps as a result of not being immunised. This does not mean for a moment that immunisation reduces the risk to nothing – the vast majority of children who develop type 1 diabetes have been immunised in infancy and there is no evidence that mumps was the trigger. It does, however, mean that as a population it is important to be aware that not getting immunisation against mumps may increase the risk of type 1 diabetes.

Even among people with similar genetic make-up (such as Caucasians living in different parts of Europe), there is up to a 10 fold difference in the likelihood of developing type 1 diabetes. For instance, children in Finland are 14 times more likely to develop type 1 diabetes than children in the former Yugoslav republic of Macedonia. Even if some of this is due to small differences in genetic make-up, it cannot account for the fact that over the course of only one or two generations, families who migrate from one part of the world to another tend to take on the risk of developing type 1 diabetes which is found in the country they migrate to.

Entire textbooks, and thousands of academic papers, have been devoted to the possible triggers of type 1 diabetes. Genetics plays a part, but so do environmental factors, which are thought to trigger the autoimmune process in which the body’s immune system turns on itself to prevent the pancreas from working. There is as yet no clear single answer, nor is there ever likely to be, since so many factors which appear to be involved. We understand that people who have a certain genetic make-up (so-called HLA susceptibility) are at higher risk of type 1 diabetes -  yet fewer that one in 10 of them go on to get type 1 diabetes. There is less than 40% ‘concordance’ in the development of type 1 diabetes even among identical twins, who have an identical genetic make-up. Genetics alone are clearly not the whole answer. We know that people exposed to some viruses are more likely to develop type 1 diabetes, yet even in congenital rubella most affected children do not go on to get the condition. In this case, it has been suggested that the fact that the virus multiplies in the pancreas may play a part. Multiple other studies have suggested that diet, including vitamin D intake in infancy, may influence to some extent the likelihood of getting type 1 diabetes. Unfortunately, as yet there is no clear evidence about which elements of diet, or what dose of vitamin D in infancy, might play a part. Parents cannot therefore take proven steps to influence their child’s risk in this way, although the existing evidence has been helpful in directing future scientific research.

There are no guarantees, and type 1 diabetes cannot be prevented. However, to state that the likelihood of getting type 1 diabetes cannot be influenced in any way is, for the clear and well proven scientific reasons above, also not true. It is clearly not feasible for families to move to a different country simply because they might, by doing so, reduce the risk of one of their children developing type 1 diabetes in the future. I highlighted this fact purely to make a contrast with type 2 diabetes, in which everyday changes to diet and lifestyle can make a vast difference to the likelihood of developing type 2 diabetes. However, as a population, the role of immunisation must be highlighted. Type 1 diabetes can be a devastating condition, and doctors have a duty not only to highlight the dramatic differences between type 1 and type 2 diabetes, which I have always been at pains to do, but to help the public to understand more about it.


  1. http://www.ncbi.nlm.nih.gov/pubmed/6383925
  2. http://www.ncbi.nlm.nih.gov/pubmed/3243043
  3. http://www.ncbi.nlm.nih.gov/pubmed/10752702
  4. http://diabetes.diabetesjournals.org/content/54/suppl_2/S125.full
  5. http://books.google.co.uk/books/about/Type_I_Diabetes.html?id=MhquYwWAHiUC&redir_esc=y
  6. http://diabetes.diabetesjournals.org/content/54/suppl_2/S125.full
  7. http://www.ncbi.nlm.nih.gov/pubmed/6383925
  8. http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(01)06580-1/abstract

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