It is true that the density of hair usually decreases steadily with advancing age. Typically, people note a slow diffuse thinning of the scalp hair starting at age 50 or older. In contrast to male pattern baldness, senile alopecia is thought to be a nonandrogen-dependent hair thinning. It involves a progressive decrease in the number of anagen follicles and hair diameter, and is often identified as a marker of systemic senescence. An important point is that patients with progeria show a phenotype of hair loss, which confirms the idea that senescent alopecia is a specific type of balding.
The following criteria have been proposed for making the diagnosis of senescent alopecia:
- hair thinning does not become apparent until approximately 50 years of age
- no family history of androgenetic alopecia
It should be noted that senescent alopecia likely coexists with androgenetic alopecia in many patients. According to the latest data, senile alopecia is associated with changes in alternative splicing, oxidative stress response, and apoptosis, which are characteristic of aging tissues. The mechanisms that lead to hair thinning and miniaturization after the age of 50 are distinct from the androgen-mediated signals. Moreover, both androgens and the level of 5a-reductase wane with age. In this case, the use of finasteride (5a-reductase inhibitor) is unlikely to lead to significant hair regrowth.
In the skin the rate of epidermal renewal and hair follicle cycling declines with age, but the reasons for this age-related loss of regenerative ability are largely unknown. A possible explanation for the observed decrease in follicle regeneration is based on a fact that the level of stem cells activation goes down with aging. To test this hypothesis scientists used different kinds of treatment (like follistatin) to reactivate hair stem cells in aging mice and the results of their research are very promising.
Nowadays there is no specific therapy for senescent alopecia. Some data even suggest that most cases of significant hair loss in the elderly are androgen driven. All in all, the whole concept of senescent alopecia is still controversial and needs to be further explored.