In August 2021 JAMA Published the US Preventive Services Task Force’s updated Recommendation Statement on Screening for Prediabetes and Type 2 Diabetes. The updated guidance differs from the 2015 recommendation statement in that the age to begin screening is lowered from 40 to 35, and it uses the term “prediabetes” to identify individuals who are at high risk for developing diabetes.
About one third of the US population is estimated to have prediabetes. So, what is “prediabetes” and why the lowered screening age?
The updated 2021 guideline recommends that clinicians screen for prediabetes and type 2 diabetes in asymptomatic adults aged 35 to 70 years who have overweight or obesity and clinicians should offer or refer patients with prediabetes to effective preventive interventions. The Task Force gave the recommendation a B grade, meaning “is a high certainty that the net benefit is moderate, or there is a moderate certainty that the net benefit is moderate to substantial.”
Prediabetes is defined by the American Diabetes Association in terms of fasting glucose ranges, glucose tolerance ranges, and HbA1c ranges. While the estimates of the risk of progression from prediabetes to diabetes vary, there is a continuous association between increasing A1c and subsequent diabetes.
A 2018 large cohort study of about 77000 individuals with prediabetes reported that the risk of developing diabetes increased with increasing hemoglobin A1c and with increasing body mass index. 2-year absolute risk of progression to diabetes ranged from less than 0.5% for those with an HbA1c of 5.7% to 5.8% without obesity, to more than 20% in those with an HbA1c of 6.3% to 6.4% with obesity.
The evidence review commissioned by the USPSTF determined that there were no strong harms from screening for prediabetes and diabetes, other than “possible short-term increases in anxiety among” screened and diagnosed individuals. The benefits of screening for prediabetes in the recommendation statement are best reflected in interventions to prevent progression of individuals with screen detected prediabetes to type 2 diabetes.
Trials assessed by the USPSTF in the evidence report published alongside the recommendation statement compared lifestyle vs pharmacologic interventions for delaying or preventing progression of prediabetes to type 2 diabetes. The report found that lifestyle interventions were significantly associated with a reduction in the incidence of diabetes. Lifestyle interventions in the assessed trials generally focused on improving diet and nutrition and increasing physical activity.
Of the pharmacologic interventions, metformin, ?-glucosidase inhibitors, and thiazolidinediones were all significantly associated with a reduction in diabetes in patients with prediabetes, though the USPSTF notes that results “for thiazolidinediones and ?-glucosidase inhibitors were limited by imprecision, inconsistency, and risk of bias [for trials of ?-glucosidase inhibitors].”
The report also noted data from the Diabetes Prevention Program Study. When comparing intensive lifestyle modification programs with metformin and placebo, there was a greater reduction in diabetes incidence with a lifestyle program than with metformin.
Lifestyle interventions were also associated with reduced systolic and diastolic blood pressure, reduced weight, and reduced BMI. However, the USPSTF found that most studies lacked the follow-up duration necessary to appropriately assess the effect of interventions for prediabetes on long term health outcomes.
But what about the lowered screening age from 40 to 35?
A 2014 study found that the number of people needed to screen to detect one positive diabetes test declines by more than half after age 35. Based on data suggesting that the incidence of diabetes increases at age 35 compared with younger ages, and on the evidence for the benefits of interventions for newly diagnosed diabetes, the USPSTF lowered the age at which to begin screening to 35.
An accompanying editorial to the USPSTF recommendation statement by Drs Edward Gregg and Tannaz Moin, published in JAMA, states that “delivery of effective preventive interventions for people with prediabetes represents an ongoing missed opportunity... the USPSTF recommendations to act early and identify and prevent diabetes may have their greatest value if they can reach young and vulnerable adults through a diverse range of effective options for prevention... Young adults appear to be the group with the most to lose by current levels of diabetes care delivery and the most to gain by attention to the new recommendation.”
It’s worth noting that other associations have different screening recommendations. While the USPSTF recommendation statement applies to nonpregnant adults aged 35-70 years who have overweight or obesity the American Diabetes Association recommends universal screening for prediabetes and diabetes for all adults 45 years or older, regardless of risk factors, and screening adults who have overweight or obesity with 1 or more risk factors, defined in the ADA guidelines, regardless of age.
The American Association of Clinical Endocrinology doesn’t limit the screening population to patients with overweight or obesity, and in the absence of other clinical risk criteria as defined in the AACE guidelines, recommends individuals age 45 years or older be screened for prediabetes or type 2 diabetes.
All 3 groups recommend screening for prediabetes and type 2 diabetes in members of at-risk populations. In the recommendation statement, the USPSTF notes that, “clinicians should consider screening at an earlier age in persons from groups with disproportionately high incidence and prevalence of diabetes or in persons who have a family history of diabetes, a history of gestational diabetes, or a history of polycystic ovarian syndrome, and at a lower BMI in Asian American persons since data suggests that a BMI of 23 or greater may be an appropriate cut point in Asian American persons.”
Based on data from 2017 to 2018, prevalence of diagnosed diabetes among US adults aged 18 years or older who identified as American Indian/Alaska Native was 14.7%, compared to 7.5% in those who identified as non-Hispanic White. 12.5% in those who identified as Hispanic/Latinx. 11.7% in those who identified as non-Hispanic Black. And 9.2% in those who identified as non-Hispanic Asian.
Read the full USPSTF statement and evidence report in the August 24/31 2021 issue of JAMA, or online at JAMA.com. Make sure to listen to the accompanying podcast, which addresses the questions and evidence discussed in this video in more detail.