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Same mortality risk seen with HbA1c levels in prediabetes, normoglycemia
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Adults with HbA1c levels in the prediabetes range do not face an increased risk for death, according to research published in Diabetes Care.
However, an observed U-shaped relationship strengthens the evidence that high and low HbA1c levels could be associated with all-cause mortality.
“Adults with prediabetes, as defined by HbA1c, did not differ in their mortality risk from those with normoglycemia,” the researchers wrote. “Known diabetes and HbA1c-defined undiagnosed diabetes were both associated with an increased risk for all-cause mortality … in this nationwide German cohort.”
Rebecca Paprott, MSc, of the department of epidemiology and health monitoring at the Robert Koch Institute in Berlin, and colleagues looked at data from 6,299 adults aged 18 to 79 years from the German National Health Interview and Examination Survey 1998, with an average follow-up of 11.6 years.
Glycemic status was defined as known diabetes (self-reported diagnosis or antidiabetic drugs) and HbA1c categories based on American Diabetes Association criteria: undiagnosed diabetes (≥ 6.5%, ≥ 48 mmol/mol); prediabetes with very high (6%-6.4%, 42 mmol/mol-46 mmol/mol) or high diabetes risk (5.7%-5.9%, 39 mmol/mol-41 mmol/mol); and normoglycemia (< 5.7%, < 39 mmol/mol).
The investigators examined the relationships between glycemic status and mortality using Cox regression, with adjustments for age, sex, education, lifestyle factors, anthropometric measures and history of chronic diseases; normoglycemia served as a reference point. Spline models were fitted to examine associations between continuous HbA1c and death among those without known diabetes.
Excess mortality risk was seen for participants with known diabetes (HR = 1.41; 95% CI, 1.08-1.84) and undiagnosed diabetes (HR = 1.63; 95% CI, 1.23-2.17) but not for those with high (HR = 1.02; 95% CI, 0.80–1.3) or very high (HR = 0.87; 95% CI, 0.67–1.13) diabetes risk.
Spline models demonstrated a U-shaped association; the lowest risk was seen at HbA1c levels from 5.4% to 5.6% (36-38 mmol/mol) and significantly increased risk at 5% or less (≤ 31 mmol/mol) and 6.4% or greater (≥ 46 mmol/mol).
“HbA1c measurements may be influenced by a number of physiological and pathophysiological conditions affecting red cell and iron metabolism, such as pregnancy, iron deficiency, chronic liver disease, alcoholism, chronic renal failure, and intake of large doses of aspirin,” the researchers wrote. “Nevertheless, results remained materially unchanged in sensitivity analyses that considered most of these factors.” – by Allegra Tiver
Disclosure: The researchers report no relevant financial disclosures.
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