Thanks for an amazing blog. I check it daily for updates. I wish I could fly to the US for a consultation one day, but it’s far away from Australia.
I have seen in a number of blog entries that you refer to hair going through a finite set of cycles (one cycle being Anagen, Catagen, Telogen). Is this based on research and/or from experience? Does all hair have a limit or does it not apply to the donor area?
The anagen, catagen, and telogen phases are the well known life cycle of any hair. I think it is even taught in high school biology. For human scalp hair, the anagen (growth) cycle can last several years. This is followed by the resting phase (catagen/telogen), lasting several weeks to months. The length of time of the anagen cycle widely varies in people, but it is estimated to be anywhere from 2 to 8 years. If you take 3 years to be an “arbitrary” average, you can calculate your lifetime of cycles. If you have genetic balding or other hair loss conditions, the cycle of hair is obviously shortened (see apoptosis). The hair cycles apply to all hairs, but the pre-programmed genetic life of certain hair is variable. You really do not need research to see this… just look at all the bald men out there!
Now, I am not sure if I have completely answered your question, as I believe there may be some misunderstanding. For men most of the hair on the back of the scalp is considered “permanent” hair which will cycle and live on (see the Norwood 7 diagram at right). The hair you see in that diagram is considered the donor hair and this is a basis of hair transplant surgery for men. The research and experience you are asking about is evident on thousands of men who have had hair transplant surgeries. For example, see the hundreds of examples posted on our site showing patients we have performed surgery on over the last 18 years — the transplanted hair is still growing and cycling. Now the aesthetics and the natural appearance is what is highly variable, depending on who performed the surgery.