in a study of nearly 337,000 people included in the UK Biobank database.
The findings suggest that people with prediabetes have “heightened risk even without progression to type 2 diabetes,” Michael C. Honigberg, MD, said at the annual scientific sessions of the American College of Cardiology.
“Hemoglobin A1c may be better considered as a continuous measure of risk rather than dichotomized” as either less than 6.5%, or 6.5% or higher, the usual threshold defining people with type 2 diabetes, said Dr. Honigberg, a cardiologist at Massachusetts General Hospital in Boston.
‘Prediabetes is not a benign entity’
“Our findings reinforce the notion that A1c represents a continuum of risk, with elevated risks observed, especially for atherosclerotic cardiovascular disease [ASCVD], at levels where some clinicians wouldn’t think twice about them. Prediabetes is not a benign entity in the middle-aged population we studied,” Dr. Honigberg said in an interview. “Risks are higher in individuals with type 2 diabetes,” he stressed, “however, prediabetes is so much more common that it appears to confer similar cardio, renal, and metabolic risks at a population level.”
Results from prior observational studies also showed elevated incidence rate of cardiovascular disease events in people with prediabetes, including a 2010 report based on data from about 11,000 U.S. residents, and in a more recent meta-analysis of 129 studies involving more than 10 million people. The new report by Dr. Honigberg “is the first to comprehensively evaluate diverse cardio-renal-metabolic outcomes across a range of A1c levels using a very large, contemporary database,” he noted. In addition, most prior reports did not include chronic kidney disease as an examined outcome.
The primary endpoint examined in the new analysis was the combined incidence during a median follow-up of just over 11 years of ASCVD events (coronary artery disease, ischemic stroke, or peripheral artery disease), CKD, or heart failure among 336,709 adults in the UK Biobank who at baseline had none of these conditions nor type 1 diabetes.
The vast majority, 82%, were normoglycemic at baseline, based on having an A1c of less than 5.7%; 14% had prediabetes, with an A1c of 5.7%-6.4%; and 4% had type 2 diabetes based on an A1c of at least 6.5% or on insulin treatment. Patients averaged about 57 years of age, slightly more than half were women, and average body mass index was in the overweight category except for those with type 2 diabetes.
The primary endpoint, the combined incidence of ASCVD, CKD, and heart failure, was 24% among those with type 2 diabetes, 14% in those with prediabetes, and 8% in those who were normoglycemic at entry. Concurrently with the report, the results appeared online. Most of these events involved ASCVD, which occurred in 11% of those in the prediabetes subgroup (roughly four-fifths of the events in this subgroup), and in 17% of those with type 2 diabetes (nearly three-quarters of the events in this subgroup).
In an analysis that adjusted for more than a dozen demographic and clinical factors, the presence of prediabetes linked with significant increases in the incidence rate of all three outcomes compared with people who were normoglycemic at baseline. The analysis also identified an A1c level of 5.0% as linked with the lowest incidence of each of the three adverse outcomes. And a very granular analysis suggested that a significantly elevated risk for ASCVD first appeared when A1c levels were in the range of 5.4%-5.7%; a significantly increased incidence of CKD became apparent once A1c was in the range of 6.2%-6.5%; and a significantly increased incidence of heart failure began to manifest once A1c levels reached at least 7.0%.