Hair Aging Revisited: An Expert Delphi Consensus on Pathogenesis, Clinical Features, and Future Therapies

Hair follicle (HF) aging is a complex process involving gradual deterioration in the function and structure of the HF, adding to degenerative changes in the hair shaft caused by weathering. Despite growing research interest, hair aging remains inconsistently defined in clinical practice, with no universally accepted classification or management guidelines. This study aimed to define hair aging and achieve consensus on diagnostic and management of hair aging.

A modified Delphi methodology was used. A European and USA-based scientific committee developed a structured questionnaire, which was distributed to a panel of 24 dermatologists in Europe. Each statement was rated on a 9-point Likert scale. Consensus was defined as a median score of 1-3 or 7-9 with < 1/3 of responses outside this range and an interquartile range (IQR) < 4.

Of the 65 statements, 51 (78.5%) reached consensus. Experts agreed that hair aging includes both quantitative and qualitative changes involving pigment loss, hair follicle miniaturization, and declining hair fiber quality. Hair graying was attributed to oxidative stress, melanocyte depletion, and diminished pigmentation-related signaling. Several contributing risk factors were identified. Senescent alopecia was defined as diffuse hair thinning in both androgen-dependent and -nondependent areas. Although diagnostic overlap with androgenetic alopecia (AGA) was acknowledged, the panel emphasized distinct underlying pathophysiology for hair aging, with stem cell exhaustion, fibrosis, and immunosenescence as suspected key mechanisms. Preventative care through lifestyle modification and supportive hair care practices was widely endorsed. Minoxidil was the only pharmacologic therapy to receive consensus support, while other emerging therapies to slow HF aging require further investigation.

This Delphi consensus provides a structured expert overview of hair aging, highlights areas of agreement and uncertainty, may assist in improving diagnostic accuracy and more consistent management strategies for age-related hair changes, and identifies potential new targets for therapeutic intervention. Graphical Abstract available for this article.