One of the most prolific areas of basic research today is on aging.  From quality of life, to the onset of diseases associated with age, a key goal is to stack the deck in favor of healthful longevity.  As a visible sign of advancing years, few physical changes are more obvious than progressive hair loss.  Even for individuals who have escaped early-onset androgenetic alopecia, the later years take their toll.

It is rare for people of either gender to reach seventy years of age with a full, intact dense head of hair.  Senescent alopecia appears to follow a somewhat different etiological path than common androgen-based pattern hair loss.  Instead of bitemporal recession and the progressive balding of the crown, a general loss of density occurs throughout the scalp.  Hair aging comprises accumulated damage to the structures producing the hair shaft and involution of the hair follicle. 

An intriguing clue into senescent alopecia may be found in a distantly related disorder, alopecia areata (AA).  In AA, it is typical for pigmented hair to be targeted for attack, but hypo-pigmented (grey) hair is often spared.  What does this tell us?  Experimental evidence supports the hypothesis that oxidative stress plays a role in skin and hair aging.  So, reagents that may blunt reactive oxygen species could hold promise in addressing senescent hair loss.

Additionally, the scalp is also subject to intrinsic or physiologic aging and extrinsic aging caused by external factors. Intrinsic factors are related to individual genetic and epigenetic mechanisms with population-based variation. Here, disease phenotypes include familial premature graying and, of course, androgenetic alopecia. Extrinsic factors include ultraviolet radiation and smoking.  The cumulative result of extrinsic factors is a negative change in the efficient maintenance of hair cycle dynamics.  Essentially, the hairs stop growing as robustly, regularly and efficiently as before.  

In our next article we will touch on some of the work currently underway to address, and possibly reverse senescent alopecia.