Ethnicity, BMI modify risk for progression toward type 1 diabetes
medwireNews: Findings from the Type 1 Diabetes TrialNet Study Group show both independent and interacting effects of ethnicity, age, and BMI on progression toward type 1 diabetes in at-risk people.
The study of 4873 autoantibody-positive relatives of patients with type 1 diabetes revealed that among the 42% who were confirmed positive for a single autoantibody, those of Hispanic ethnicity were a significant 34% less likely than White participants to progress to being positive for multiple autoantibodies.
The association persisted after accounting for age, sex, positive autoantibody type, obesity, HLA-DR3-DQ2/DR4-DQ8 genotype, and diabetes risk according to Diabetes Prevention Trial–Type 1 Risk Score, report Mustafa Tosur (Baylor College of Medicine, Houston, Texas, USA) and co-researchers.
“The slower progression in Hispanic individuals suggests a lower frequency of predisposing characteristics beyond those that we adjusted for,” the team writes in Diabetologia.
They note that fewer Hispanic than White study participants were multiple autoantibody positive at enrollment (48 vs 60%), in line with their slower progression, and suggest that the ethnic differences in progression would be even more marked if at-risk people were monitored from birth.
The study cohort was 11.0% Hispanic people, 80.9% White people, 2.9% Black people, and 5.2% other ethnicities. The participants’ median age was around 12 years, but ranged from 1 to 52 years of age. During follow-up, 12.0% progressed to type 1 diabetes, giving an estimated 5-year cumulative incidence of 39.0% for those with multiple autoantibodies and 26.4% for the whole cohort.
Ethnicity had no overall effect on progression to type 1 diabetes in the 58% of participants with multiple autoantibodies, but it did interact with the effects of BMI in younger study participants.
In these people – children younger than 12 years with multiple autoantibodies – being overweight or obese significantly increased the risk for progressing to type 1 diabetes. However, this risk was particularly marked in Hispanic children, in whom being overweight or obese increased the risk for progression 3.8-fold. In White children, the BMI-associated risk increase was a more modest 1.36-fold.
BMI also appeared to have a significant effect in older Hispanic participants, but the researchers regard this only as “an interesting and hypothesis-generating observation,” given that there were just 13 events in this subgroup.
They suggest the ethnic-specific effect of BMI could be because of its tendency to underestimate body fat in Hispanic people, resulting in increased adiposity, and therefore higher insulin resistance, in Hispanic versus White participants with the same BMI.
“Counselling family members regarding type 1 diabetes risk is an integral part of modern diabetes care,” say Tosur et al. They suggest a specific emphasis on the risk associated with overweight and obesity when counseling Hispanic families with young at-risk children.
“This knowledge may encourage Hispanic families to make healthy lifestyle changes,” they hope.
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