I found out during my time as a volunteer in a nursing home that the smell is mostly due to improper bathing by their caretaker. If anyone is not bathed regularly and completely, they will develop “old people” smell.
There is another factor that has might be considered. per wikipedia: In the April 2001 issue of the Journal of Investigative Dermatology, Shinichiro Haze et al. published an article suggesting that omega-7 unsaturated fatty acids, such as palmitoleic acid and vaccenic acid found on the skin surfacewere oxidatively decomposed to 2-nonenal, which may be the cause of the phenomenon commonly known as old person smell.
A scientist in Japan, Shoji Nakamura is devising products for a cosmetic line to meet the market”, but in my opinion, washing properly is all that is needed.