Histopathology of aging hair follicles

Hair, like all growing parts of the body experiences aging. From thinning, to pigmentation, aging produces significant changes in hair follicles that are visible to all. These changes, although completely natural and unavoidable, may cause discomfort or uneasiness in some, but what actually happens to hair follicles when a person gets older?  


Graying of hair 

The most common aspect of aging hair is surely the graying of hair, which occurs in almost all individuals, although in various degrees and at different stages in life. As a rule of thumb the graying of hair is usually 50-50-50, as in by the age of 50, 50% of the population has 50% of graying hair. However, the onset of graying hair differs in various ethnicities. For instance, in Caucasians, the age of onset is commonly 34 ± 9.6 years, while in Africans the average age of onset is considered to be 43.9 ± 10.3 years. Studies claim that by the age of 60 all individuals are prone to have at least some degree of graying hair, regardless of their ethnicity and genetics.

aging of hair folliclesAlthough this phenomenon affects both genders equally, many studies show that graying usually happens in one gender earlier than others in different ethnicities. For example, in the Japanese population men are seen to have gray hair in their early 30’s whereas, in Japanese women graying normally occurs in their late ’30s. The pattern of this loss of pigmentation also varies from gender to gender, with men’s temples and sideburns aging first, and the loss of pigmentation then spreading to the vertex and remainder of the scalp. However, in women, gray hair starts to show first in the center lines of the scalp.

The process starts with a gradual decrease in the number and activity of cells responsible for melatonin production (aka melanocytes) and ending in their disappearance from the hair bulb. Nevertheless, some resting melanocytes may still reside at the base of the hair bulb, and might allow repigmentation of hair under certain conditions and stimuli.


Dry brittle hair

The decrease in melanocytic activity and accompanying melanin production also leaves the hair shaft thin, opaque, dry, and fragile. These changes are also related to the alteration of hair follicular anatomy such as an increase in the curvature of the hair shaft.


Senile alopecia

Senile alopecia is often mistaken for androgenetic type alopecia due to its high prevalence in most populations. However, contrary to what is commonly believed, these two types of hair loss are not significantly related. Studies in fact show that senile alopecia manifests itself after the age of 50, whereas androgenetic alopecia does not follow any specific timeline and can occur at any age following puberty. 

Similarly, hair loss due to aging is also not related to the change in androgen levels and therefore, can involve all or any hairy part of the body. The characteristic features of senile alopecia are the decrease in hair strand thickness and length. 

On the other hand, hair loss as a consequence of aging remains controversial, as a number of studies state that aging itself does not cause significant hair loss, with it accounting only for 0.22% of the total number of hair shed per year. This low percentage of hair loss is therefore not enough to be labeled as senile alopecia according to many experts, who suggest that it can coexist with any other type of alopecia. Most importantly studies show that the co-existence of senile alopecia with androgenetic type is fairly common among the elderly.


Miniaturization of hair follicles

Miniaturization is the thinning of hair follicle diameter over time. The hair follicle diameter is what decides the thickness of a single hair strand. From childhood to youth this diameter is continually increasing, peaking around the age of forty in women, and around the age of twenty in men, after which the diameter starts a progressive decline, leading to the thinning observed in aging hair.


Aging of hair follicles

The aging of hair follicles is a natural and unavoidable part of life that is genetically predetermined since birth. Nevertheless, contributing factors such as environmental elements, stress and inflammatory conditions are also known to accelerate its process. The only way to postpone it or try to limit it lies in the residual inactive melanocyte that persists in the base of the hair follicles. Much effort is in fact being directed in trying to activate these cells in order to stimulate the repigmentation of graying hair.  



Whiting DA. How real is senescent alopecia? A histopathologic approach. Clinics in dermatology. 2011 Jan 1;29(1):49-53.

Sperling LC, Cowper SE, Knopp EA. An atlas of hair pathology with clinical correlations. CRC Press; 2012 May 24.

Sinclair R, Chapman A, Magee J. The lack of significant changes in scalp hair follicle density with advancing age. British Journal of Dermatology. 2005 Apr;152(4):646-9.

Birch MP, Messenger JF, Messenger AG. Hair density, hair diameter and the prevalence of female pattern hair loss. British Journal of Dermatology. 2001 Feb;144(2):297-304.

Tajima M, Hamada C, Arai T, Miyazawa M, Shibata R, Ishino A. Characteristic features of Japanese women’s hair with aging and with progressing hair loss. Journal of dermatological science. 2007 Feb 1;45(2):93-103.

Robbins C, Mirmirani P, Messenger AG, Birch MP, Youngquist RS, Tamura M, Filloon T, Luo F, Dawson Jr TL. What women want–quantifying the perception of hair amount: an analysis of hair diameter and density changes with age in Caucasian women. British Journal of Dermatology. 2012 Aug;167(2):324-32.

JACKSON D, Church RE, Ebling FJ. Hair diameter in female baldness. British Journal of Dermatology. 1972 Oct;87(4):361-7.

Courtois M, Loussouarn G, Hourseau C, Grollier JF. Hair cycle and alopecia. Skin Pharmacology and Physiology. 1994;7(1-2):84-9.

Otsuka H. Study on Japanese hair. J Jpn Cosmet Sci Soc. 1988;12(3):192-7.

Keogh EV, Walsh RJ. Rate of greying of human hair. Nature. 1965 Aug;207(4999):877-8.

Panhard S, Lozano I, Loussouarn G. Greying of the human hair: a worldwide survey, revisiting the ‘50’rule of thumb. British Journal of Dermatology. 2012 Oct;167(4):865-73.

Goodier M, Hordinsky M. Normal and aging hair biology and structure ‘aging and hair’. InAlopecias-Practical Evaluation and Management 2015 (Vol. 47, pp. 1-9). Karger Publishers.