Loss of sex drive
My wife (52) and I (61) have been married 12 years. Our sex life has gone from twice a week to once a month.
I have lost interest due to other personal worries. Is this normal?
Your focus shouldn't be on whether it is normal, but on whether it is a problem for you or your wife. If not, fine. If so, try to address it.
Regardless of whether or not it's normal (and there is really no such thing as normal), does it bother you? I assume that since you are posting that it has somewhat of an impact on your relationship. Have you discussed this with your wife and/or is this a source of contention between the two of you?
It sounds entirely normal. What you have to decide is if you're both comfortable with that, able to accept it in the short term as an unavoidable side effect of something else or whether you'd like your interest to revive.
If it's not the first then I suggest you look at resolving whatever is causing your 'other personal worries' and see if that helps.