Rahul Aggarwal was in medical school when he got the surprising news that his mother—a fit woman in her 40s—had been diagnosed with type 2 diabetes. “I always thought of diabetes as a disease of people at higher weights and with certain lifestyle practices,” he recalls, “but my mom was an Indian American woman with a healthy weight and good diet and exercise practices.” Aggarwal, now a clinical fellow at Beth Israel Deaconess Medical Center in Boston, began thinking about how diabetes seems to disproportionately affect certain ethnic and racial groups. Those musings were the seed of an eye-opening study published earlier this year in the Annals of Internal Medicine. It quantified diabetes risk in minority groups to determine if current screening recommendations are equitable. Spoiler alert: they are not.
The current standard was released in 2021 by the U.S. Preventive Services Task Force (USPSTF), which issues evidence-based guidance on disease prevention. The recommendation is to test adults aged 35 to 70 for diabetes if they are overweight or obese, defined as having a body mass index (BMI) of 25 kg/m2 or more. Aggarwal and his collaborators looked at the lowest-risk individuals eligible for screening under that rubric: 35-year-olds who are just barely overweight (with a BMI of 25). Within this cohort about 1.4 percent of white Americans have blood glucose levels in the diabetic range, so the researchers were shocked to find that the rate was about double for Hispanics and even higher among Black and Asian Americans. They concluded that to detect diabetes equally across all these groups, you would need to test Asian Americans with a BMI of 20 and Black and Hispanic individuals with a BMI of just 18.5—measures considered to be in the healthy range.
In a second analysis, the investigators looked at diabetes prevalence by age and concluded that to match the efficacy of screening white people at 35, providers would need to screen Hispanic Americans at 25, Asian Americans at 23 and Black Americans at 21. Medicine has been eliminating race-based scoring that made some tests, such as an assessment of kidney function, less sensitive to disease in Black people. But in the case of diabetes screening, the one-size-fits-all standard may be the problem.
Because diabetes is a complex disease involving diet, life habits, genetics and psychosocial factors, it's not easy to say why vulnerability would vary among demographic groups. There is some evidence that Asian Americans have more abdominal fat at lower body weights than do people of other ethnicities, which raises risk. “A lot of studies suggest it's better to measure the waist-hip ratio instead of using BMI [to assess risk],” says Quyen Ngo-Metzger of the Kaiser Permanente Bernard J. Tyson School of Medicine. Chronic stress has also been linked to diabetes risk, she says, and that could include the stress of experiencing racism.
Ngo-Metzger, who was the USPSTF's scientific director from 2012 to 2019, notes that “most studies of diabetes were done in middle-aged white individuals,” and that's what screening standards were based on. She argues that they should be revised. “The study found that you would miss so many Blacks, Hispanics and Asians when you use these guidelines. I think it's a disservice.”
The USPSTF is unlikely, however, to revisit its guidelines soon, usually waiting three to five years, says Michael J. Barry of Massachusetts General Hospital, a task force vice chair. The USPSTF is committed to health equity, he says, but it needs more evidence that altering its recommendations would result in better long-term outcomes for patients—an issue the new study does not address.
Still, it seems obvious that detecting—and treating—diabetes earlier in communities where it is often missed would lead to improved health. Harvard University cardiologist Dhruv Kazi, senior author on the Annals study, points out that diabetes takes an outsize toll on Americans of color. “Black individuals with diabetes are more than twice as likely to end up on dialysis than white individuals with diabetes,” he notes. They are also more likely to lose limbs and vision to undertreated diabetes. Kazi attributes these tragic disparities to “structural” inequities such as poor access to health care, high-quality food and opportunities for exercise.
Like Ngo-Metzger, Kazi would like to see screening guidelines better reflect individual risk factors that include race and ethnicity. Without such changes, he says, insurers may refuse to cover diabetes testing in people who have a BMI below 25 or who are younger than 35. Fixing larger social inequalities would require major changes, Kazi concedes, “but making screening more equitable is a good place to start.”