Evidence check: HbA1c in the context of skin aging

HbA1c is a marker of long-term blood glucose control, reflecting average levels over 2–3 months. In the context of skin aging, mechanistic evidence suggests that elevated glucose promotes non-enzymatic glycation, forming Advanced Glycation Endproducts (AGEs). These AGEs can cross-link collagen and elastin, reducing skin elasticity and contributing to wrinkle formation and premature aging. However, the evidence is primarily from in vitro and animal studies; robust human prospective trials directly linking HbA1c to skin aging are limited. Some cross-sectional studies show associations between higher HbA1c and visible skin aging signs, but causality remains uncertain, especially in non-diabetic individuals. Therefore, HbA1c as a biomarker for skin aging is best classified as mechanistic rather than strongly evidence-based. For personalized assessment, factors like UV exposure, lifestyle, and genetics are more relevant. A standalone HbA1c test is not recommended for skin aging screening.