The study found that both blacks and whites face the similar risk of evolving diabetes when all biological factors for the disease are considered over time. The finding flips long-held beliefs that there is an unexplained or genetic reason why blacks have double the rate of diabetes linked to whites by midlife, which is considered early onset. This study was published in the journal JAMA.

Previous studies have found higher rates of diabetes in blacks are still present even when risk factors for diabetes such as obesity and lower socioeconomic status are considered. But this study identified a combination of modifiable risk factors over the time body mass index, fat around the abdomen, fasting glucose levels, lipids, blood pressure and lung function that drive the higher rate of diabetes. When these were factored out, there were no disparities between black and white men or women.

"Blacks gained more weight over time," Carnethon said. "It was the accumulation of this and other risk factors that eliminated the so-called mysterious cause of the disparity." In previous studies, researchers measured such health behaviors as obesity, physical activity and diet once during their study participants' lives. But these factors can change over time, and how much they turn may be different in each race group. The North-western study measured these changes in her weight over time, along with changes in other related health behaviors and health risk factors.

When scientists accounted for these changes in risk factors for diabetes, they did not observe race differences in the development of diabetes.The findings are particularly significant because the incidence of diabetes is rising in black youth ages 10 to 19 years old. Another recent study showed from 2002 to 2012 the rate of diabetes remained stable for non-Hispanic white youth (ages 10-19) but increased annually by more than 6 percent for non-Hispanic black youth.

Michael Bancks said, "To eliminate the higher rate of diabetes, everybody needs to have access to healthy foods, safe spaces for physical activity and equal economic opportunity to have enough money to afford these things and live in communities that offer this." The North-western study sample included 4,251 individuals from the original study. Individuals were followed through 2015 to 2016 for the development of diabetes, which was assessed at eight follow-up examinations over these 30 years using standard diagnostic criteria for diabetes.

Carnethon concludes from this study that high-risk factors would eliminate the disparity. As they are not able to reduce and there is no mystery for these higher rates. Our efforts to control the traditional risk factors can work to decrease the disparities observed in diabetes incidence.