According to a study by researchers at the Johns Hopkins Bloomberg School of Public Health, older adults classified as “prediabetes” because of moderately high blood sugar levels do not usually develop full-blown diabetes.
Doctors still consider prediabetes to be a useful indicator of future diabetes risk in young and middle adults. However, the study, which involved nearly 3,500 older adults, mean age 76, for about six and a half years, suggests that prediabetes is not a useful marker of diabetes risk in people of advanced age.
The results were published in JAMA Internal Medicine on February 8th.
“Our results suggest that in older adults with blood glucose levels in the prediabetes range, few actually develop diabetes,” says lead author Elizabeth Selvin, PhD, professor in the Epidemiology Division at Bloomberg School. “The prediabetes category doesn’t seem to help us identify people at high risk. Instead, doctors should focus on healthy lifestyle changes and key disease risk factors such as smoking, high blood pressure and high cholesterol.”
Type 2 diabetes results in chronically excessive blood sugar levels, which places stress on organs including the kidneys, weakens the immune system, damages blood vessels and promotes heart disease and strokes, among other things. The prevalence of diagnosed type 2 diabetes in the US has increased from less than 1 percent in the 1950s to more than 7 percent today – and researchers believe the real number, including undiagnosed diabetes, is now over 12 percent . This sharp increase is due to the aging US population and the increased rates of overweight and obesity.
Doctors have used the concept of prediabetes – blood sugar levels that are higher than normal but not yet in the diabetic range – as an indicator of an increased risk of diabetes in younger and middle-aged people. However, the usefulness of the concept in older adults – particularly those over 70 – was less clear.
“It is very common for older adults to have at least slightly elevated blood sugar levels, but how likely it is that they will develop diabetes is an unresolved question,” says Selvin.
To get a better picture of how older adults with prediabetes fare, Selvin and colleagues turned to the study of atherosclerosis risk in communities. This large epidemiological cohort project, funded by the US National Heart, Lung, and Blood Institute and involving both black and white participants, has been running at four US medical centers, including Johns Hopkins, since 1987. For their prediabetes analysis, the researchers selected 3,412 ARIC study participants who had attended a follow-up visit between 2011 and 2013 – at a time when the participants were between 71 and 90 years old – and who had no history of diabetes. The researchers then looked at how the participants’ blood glucose measurements had changed during the 2016-17 period during the next control visit.
As expected, the researchers found that “prediabetes,” as defined by two different blood tests, was very common among those attending the 2011-13 visit. Those with prediabetes, defined by moderately high blood sugar levels after an overnight fast (the impaired fasting glucose test, or IFG), made up 59 percent of the original sample, and those with prediabetes who were defined with another blood test for glycated hemoglobin (HbA1c). made up 44 percent of the initial sample.
However, the results showed that only a small number of the participants with prediabetes in the 2011-13 period had diabetes at the time of the 2016-17 visit – 8 percent of IFG-defined prediabetics and 9 percent of HbA1c-defined prediabetics.
In contrast, 44 percent of the IFG group and 13 percent of the HbA1c group had improved so much by the 2016-17 visit that their test results were back to normal. In addition, 16 and 19 percent of these two groups had died of other reasons in the 2016-17 visit.
The results show that older adults with prediabetes at intervals like the one in the study are more likely to have lower blood sugar levels – or to die for other reasons – than to develop diabetes.
“It seems that ‘prediabetes’ is not a robust diagnosis in older adults,” says Selvin.
“Our results support a focus on lifestyle improvements, including exercise and diet, when feasible and safe, for older adults with prediabetes,” said Mary Rooney, PhD, postdoctoral fellow at Bloomberg School and first author of the paper. “This approach has far-reaching benefits for patients.”
Selvin and her colleagues recommend that physicians in older adults should focus their screening efforts on risk factors, such as high blood pressure, which are more useful in predicting disease and mortality in this population.
Bloomberg School of Public Health at Johns Hopkins University