Deterioration and halacha

 It is a clear halacha that even if a parent or talmid chachom deteriorates he is still to be treated with kavod.

But what if it is a spouse who deveopd mental issues or dementia or diabetes or Parkinson's disease after decades of marriage. Is Divorce advisable?

What if this occurs after a couple become engaged or it is discovered  that there was a serious health condition that they had concealed

In a normal situation where there is something intolerable so we say it is just tough accept this as your burden or get a divorce. Chazal say even if you don't like your wife's cooking it is grounds for divorce