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Nontraditional risk factors may account for racial differences in type 2 diabetes
Racial disparities in type 2 diabetes prevalence may be mediated by nontraditional risk factors, such as lung capacity and blood levels of potassium, according to study results.
“We were surprised at the findings,” Ranee Chatterjee, MD, associate professor of general internal medicine at Duke University School of Medicine, said in a press release. “It’s not clear how these nontraditional risk factors mediate the racial disparities in diabetes risk, but they suggest there are additional biological or environmental causes driving this disparity.”
The prospective cohort study analyzed data from 2,322 black and 8,840 white participants enrolled in the Atherosclerosis Risk in Communities (ARIC) study.
All study participants were screened at a baseline visit between 1987 and 1989, at which time none had diabetes, and at subsequent in-person follow-up every 3 years during a 9-year period. Subsequent telephone follow-up was conducted annually through 2006.
Incident diabetes was the study’s main outcome, and participant-reported race was the main exposure in the mediation analysis. The researchers identified traditional risk factors, such as age, BMI, waist-to-hip ratio, family history of diabetes, hypertension, physical exercise, smoking status, socioeconomic factors, and blood levels of creatinine, glucose and insulin.
Nontraditional risk factors also were evaluated, including blood levels of potassium and magnesium, dietary fiber, uric acid, heart rate, activated partial thromboplastin, von Willebrand’s factor, hematocrit, white blood count, actual forced vital capacity (FVC), number of years at residence, and longest held occupation.
Cox regression was used to determine the relationship between incident diabetes and race during the 9-year in-person follow-up. The mediation effect of each covariate was determined based on the percent change in the coefficient of race in multivariate models with and without the covariate of interest.
The researchers found black race to be independently associated with incident diabetes. BMI, FVC, systolic blood pressure and serum potassium were found to be the most significant mediators of the link between diabetes risk and race, with mediation effects of 22% for BMI, 21.7% for FVC, 17.9% for systolic BP and 17.7% for serum potassium during 9 years of in-person follow-up. These mediation effects remained consistent in the subsequent 17 years of telephone follow-up.
Particularly noteworthy was the high mediation effect seen in FVC, which is a measure of lung function. At 21.7%, it was found to be nearly equally responsible for increased diabetes risk in blacks as more traditional risk factors such as obesity, which had a 22% mediation effect.
Disclosure: The researchers report no relevant financial disclosures.