How are HbA1c and longevity related?

HbA1c (glycated hemoglobin) is a well-established biomarker reflecting average blood glucose over the past 2–3 months. Elevated HbA1c is strongly linked to diabetes, cardiovascular disease, and accelerated aging. Even high-normal HbA1c levels in non-diabetic individuals are associated with increased all-cause mortality and reduced life expectancy. Mechanistically, chronic hyperglycemia drives oxidative stress, inflammation, and non-enzymatic glycation of proteins—processes that directly contribute to biological aging. Conversely, maintaining HbA1c below 5.7% is associated with lower cardiovascular and renal morbidity and potentially longer healthspan. However, evidence for a causal extension of maximum human lifespan is limited; the association is robust but confounded by lifestyle factors (diet, exercise). HbA1c testing is a useful risk assessment tool but not a direct 'longevity marker.' Its predictive value is moderate in non-diabetic populations. In summary, HbA1c is an important indirect predictor of healthy aging, not longevity per se.