Will PRP work in someone who is a 70 year old female?

This needs an in-person evaluation. I suggest seeing a hair loss expert now to evaluate and go over your condition and provide you information about your best treatment options. There are great non-invasive options like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer

PRP treatments are fast growing in popularity. While there is a good deal of anecdotal data on its positive effects, there is very little randomized controlled (i.e. high quality) data available. With respect to hair restoration, proponent have demonstrated impacts ranging from slowing/cessation of loss to thickening/strengthening of hair. Some will claim to have demonstrated regrowth.
Ultimately, there is very little drawback or risk to the procedure with the potential for significant reward. While the mechanism of action is not entirely clear, the effect will likely be rooted in the native concentration of growth factors in any given patient's plasma. Some will have better quality or more concentrated plasma than others. The results range from decreased hair loss to thickening of existing or emerging hairs to increased growth. Ultimately, the variability in response is likely linked to the inherent (i.e. genetic) quality of the plasma which will differ from one patient to the next.
PRP has (anecdotally) proven to be effective in the arena of hair restoration both as an adjunct to grafting as well as standalone treatment for those who may not (yet) be a candidate for grafting. Patients have demonstrated slowed loss, thickening of existing hair and regrowth. The typical duration of effect is 6-9 months with most patients being treated 2x yearly (at least initially).
With regards to your specific question, as long as you have adequate platelet counts you are a candidate. However, these counts do vary with age and in my experience younger patients do have a more vigorous response. That is not to say older patients will not have a response, however they may need to temper expectations.
As always, discuss your concerns with a board certified plastic surgeon (ABPS), with experience in hair restoration.
Donovan Rosas MD
Board Certified by the American Board of Plastic Surgery
Member: American Society for Aesthetic Plastic Surgery, American Society of Plastic Surgeons
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The amount of platelets in the blood decreases with increasing age. A minimum of 105,000 platelets is necessary to have an adequate response with PRP. Interestingly, platelet activity increases as age increases. The amount of increased activity has not been studied after the age of 50. Have a platelet count done and you can determine if you are a candidate for PRP for hair. Jeff Rapaport MD FAADRealself Verified All-star