Signaling pathways in hair aging

Hair follicle (HF) homeostasis is regulated by various signaling pathways. Disruption of such homeostasis leads to HF disorders, such as alopecia, pigment loss, and hair aging, which is causing severe health problems and aesthetic concerns. Among these disorders, hair aging is characterized by hair graying, hair loss, hair follicle miniaturization (HFM), and structural changes to the hair shaft. Hair aging occurs under physiological conditions, while premature hair aging is often associated with certain pathological conditions. Numerous investigations have been made to determine the mechanisms and explore treatments to prevent hair aging. The most well-known hypotheses about hair aging include oxidative stress, hormonal disorders, inflammation, as well as DNA damage and repair defects. Ultimately, these factors pose threats to HF cells, especially stem cells such as hair follicle stem cells, melanocyte stem cells, and mesenchymal stem cells, which hamper hair regeneration and pigmentation. Here, we summarize previous studies investigating the above mechanisms and the existing therapeutic methods for hair aging. We also provide insights into hair aging research and discuss the limitations and outlook.

Hair Aging and Hair Disorders in Elderly Patients

Hair loss in elderly patients is a common complaint. It can be related to different conditions that affect patients' quality of life and represents a challenge for dermatologists. It affects both men and women during the aging process with an estimated percentage of balding after 65 years of age of 53% and 37%, respectively. Androgenetic alopecia, frontal fibrosing alopecia, senile alopecia, and erosive pustular dermatosis of the scalp are the hair diseases most frequently described in this age group. The objective of this review is to summarize the current knowledge about alopecia affecting elderly patients, differentiating between chronological hair aging signs and pathological changes, to help clinicians, offer an adequate management of these disorders to their patients.

Hair Aging in Different Races and Ethnicities

BACKGROUND: Aging is an unavoidable biological process with many influencing factors, accounting for a multitude of visible manifestations on the hair as well as the skin. As the population ages while becoming more diverse, it is increasingly important to better understand the hair aging process. METHODS: A literature search was performed to review what is known about changes in hair structure over time, focusing on the differences in hair aging according to ethnic background. RESULTS: Sixty-nine publications were selected and information regarding hair structure, aging characteristics, and responses to extrinsic damage together with differences between races and ethnicities was collected. Hair-graying onset varies with race, with the average age for Caucasians being mid-thirties, that for Asians being late thirties, and that for Africans being mid-forties. Caucasians and Asians typically experience damage to the distal hair shaft, while African-Americans see damage occurring closer to the hair root. Postmenopausal changes include decreased anagen hairs in the frontal scalp, lower growth rates, and smaller hair diameters. CONCLUSION: There is a paucity of literature examining the characteristics of hair aging across all races. The unique characteristics of hair aging in different ethnicities provides information that will aid in a culturally sensitive approach and recommendations.