Senescent alopecia, sometimes known as “senile alopecia”, is when the scalp hairs become extremely thin in diameter. It is a form of alopecia that accompanies old age, and can only be diagnosed once all other possible factors have been exhausted.
This form of alopecia is caused by a process known as miniaturization, which is where the hair follicles begin to shrink over time. While male pattern hair loss (MPH) and female pattern hair loss (FPH) also involves a miniaturization of the hair follicles, the main difference between these two types of hair loss and senile alopecia is the extent of hair loss that an individual will experience. A person with MPH will most likely lose the majority of their hair, and a person with FPH may show signs of balding as well (though to a much lesser degree). However, with senescent alopecia, the scalp typically does not become bald at all – the hair loss simply becomes diffuse, which means the hair becomes uniformly thin throughout all regions of the scalp.
Although the exact cause is unknown, researchers theorize that senescent alopecia is created by a different set of genes than those responsible for MPH or FPH. This may be why a person can resist a hormone called dihydrotestosterone (DHT) for their entire life, yet still develop a miniaturization of the hair follicles much later on. In certain individuals with MPH or FPH, DHT gathers in the scalp’s tissues and prevents the hair follicle from reaching its blood supply. This causes the hair follicle itself to shrink to the point where hairs will no longer grow. However, people with senescent alopecia have often shown no susceptibility to DHT, yet somehow experience miniaturization. However, unlike MPH and FPH, senile alopecia never forces these follicles to fully shrink.
A 2011 study conducted in Dallas, Texas takes a close look at 2,149 scalps that were thought to have MPH, female pattern hair loss (FPH), or other forms of alopecia. The data were acquired from the same sources for a number of years so that the number of follicular units could be measured over the course of decades. The patients ranged from twenty-years-old to ninety-nine-years-old at the time of study completion, and the goal was to see how many of these scalp specimens could potentially be undiagnosed cases of senile alopecia.
The study finds that most of the cases were directly related to DHT, and that only a very small number of specimens had a source of hair loss that could not be identified. As the study concludes, “old age is not a significant cause of hair loss”, although it sometimes is also the only possible explanation. The bottom line is most people will not develop senile alopecia. In fact, it is one of the rarest types of alopecia possible. However, it is still a possibility, no matter how seemingly remote.
As of now, there are no viable treatments for this rare type of hair loss. A hair transplant is not possible due to a lack of suitable donor hair, and the follicles are most likely too advanced with age to respond to medication. However, new areas of research, such as platelet-rich plasma therapy and hair cloning, may provide a solution in the near future.
It should be noted that while senescent alopecia is not caused by DHT it is often accompanied by additional hair loss that is due to DHT so the two conditions are not mutually exclusive.