Being studied now!
Seems a quite active area for research now.
Much would depend on reasons for the loss of smell sense. Also, without a trauma or disease cause, there are studies looking into that as a very early indicator of future alzheimer's or parkinson's. Efforts are all over the MAP - it's an interesting question. Some love this sense - others care less. I'd miss it a lot, so if this is you, i feel your loss.