It says at the bottom of the Amud that until the time of Avraham Avinu their was no old age(Pashtus meaning looking old which is how the gemara is mashmah as its talking about people coming to avraham instead of yitzcok and vice versa).
yet it said earlier that Sara was old(as it sais that the wrinkels went away, showing us clearly the she looked old)
Rueven Naftali, passaic
The Maharsha (DH v'Havei Ziknah) explains (he has other questions) that Ziknah existed before, but Avraham Avinu asked for whitening of the hair to make it noticeable. This could mean that even with wrinkles, mistakes of identity could happen, but not when the hair whitens. If so, there is no question from Sarah's wrinkles.
Additionally, one can say that only by women does someone beyond child-bearing age look different from one younger, and that always existed. The Kematim, folds in the skin, could be a result, but were not a sign of being extremely aged.
All the best,
Reuven Weiner