medwireNews: The risk associated with a family history of type 2 diabetes is highest for people whose near relatives were diagnosed with the condition at a young age, show registry data.
“Accurate registration of age at diagnosis should form an integral part of recording a diabetes family history, as it provides easily obtainable and highly relevant detail that may improve identification of individuals at increased risk of developing type 2 diabetes at a younger age,” say the researchers.
“In particular, these individuals may benefit from closer risk factor assessment and follow-up, as well as prevention strategies that may involve the family.”
The team studied data from 2,000,552 people living in Denmark who were at least 30 years old or attained that age between 1995 and 2012. During a median follow-up of 14 years, 76,633 of these people developed type 2 diabetes.
The incidence rate ratio (IRR) of type 2 diabetes rose with increasing number of close relatives who also had the condition, and the researchers found this to follow “a nearly multiplicative pattern,” starting at 1.60 for people who had a half sibling with diabetes and rising to 11.50 for women who had both parents plus a full sibling with diabetes.
But these associations were modified by the age of the relative at diagnosis, report Omar Silverman-Retana (Aarhus University, Denmark) and study co-authors in Diabetologia.
For example, the IRR for diabetes associated with having a mother with the condition was approximately 4.0 if the mother was diagnosed at age 50 years, but only 1.5 if she was diagnosed at the age of 80 years.
“The larger risk conferred by parents who are diagnosed with diabetes at a younger age may be the consequence of both a stronger familial genetic susceptibility and a stronger inherited familial diabetogenic environment,” the team suggests.
They note that their findings “can also be expressed as an age difference in reaching a given level of risk.”
So for example men who had a mother with type 2 diabetes would reach a cumulative 2% diabetes incidence by the age of 64 years if their mother was diagnosed at age 70, but they would reach that same risk level by the age of 56 years if their mother was diagnosed at the age of 50.
“These results show that the two features (age at diagnosis and diabetes risk) are not two separate phenotypes but two sides of the same coin,” write the researchers.
They caution, however, that the national registry used only records diabetes cases at the first use of medication, so the actual age at first diagnosis could have been younger for many people.
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Diabetologia 2020; doi:10.1007/s00125-020-05113-8