How meaningful is prediabetes for older adults?

A few years ago, routine lab tests showed that Susan Glickman Weinberg, then a 65-year-old clinical social worker in Los Angeles, had what her doctor said was "prediabetes."

A measure of how much sugar has been circulating in her bloodstream over time, a hemoglobin A1C reading, was 5.8%, barely above normal. If her results reached 6% — with diabetes defined at 6.5% — her doctor said he would recommend the drug metformin.

"The thought that maybe I'd get diabetes was very upsetting," she said. "There were a lot of unknowns."

Now, there are fewer unknowns. A longitudinal study of older adults, published online this month in the journal JAMA Internal Medicine, provides some answers about the very common in-between condition known as prediabetes.

The researchers found that over several years, older people who were supposedly prediabetic were far more likely to have their blood-sugar levels return to normal than to progress to diabetes. And they were no more likely to die during the follow-up period than their peers with normal blood sugar.

"In most older adults, prediabetes probably shouldn't be a priority," said Elizabeth Selvin, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health in Baltimore and the senior author on the study.

Prediabetes refers to a blood-sugar level that is higher than normal but that has not crossed the threshold into diabetes. It is commonly defined by a hemoglobin A1C reading of 5.7 to 6.4% or a fasting glucose level of 100 to 125 mg/dL; in midlife, it can portend serious health problems.

A diagnosis of prediabetes means that you are more likely to develop diabetes, and "that leads to downstream illness," said Dr. Kenneth Lam, a geriatrician at the University of California, San Francisco, and an author of an editorial accompanying the study. "It damages your kidneys, your eyes and your nerves. It causes heart attack and stroke."

But for an older adult just edging into higher blood sugar levels, it's a different story. Those consequences take years to develop, and many people in their 70s and 80s will not live long enough to encounter them.

Selvin and her colleagues analyzed the findings of a continuing national study of cardiovascular risk that began in the 1980s. When 3,412 of the participants showed up for lab tests between 2011 and 2013, they had reached ages 71 to 90 and did not have diabetes. However, almost three-quarters qualified as prediabetic.

These findings mirrored a 2016 study pointing out that a popular online risk test created by the Centers for Disease Control and Prevention and the American Diabetes Association — and accessible at doihaveprediabetes.org — would deem nearly everyone older than 60 as prediabetic.

In 2010, a CDC review reported that 9 to 25% of those with an A1C of 5.5 to 6% will develop diabetes over five years; so will 25 to 50% of those with A1C readings of 6 to 6.5%. But those estimates were based on a middle-age population.

When Selvin and her team looked at what had happened to their older prediabetic cohort five to six years later, only 8 to 9% had developed diabetes. A much larger group — 13% of those whose A1C level was elevated and 44% of those with prediabetic fasting blood glucose — saw their readings revert to normal blood sugar levels.

"We're not seeing much risk in these individuals," Selvin said. "Older adults can have complex health issues. Those that impair quality of life should be the focus, not mildly elevated blood glucose."