From DR John:
I share the same fear. Dad had it. Mom, at her age, is now doing what Dad always fessed: She’s losing her English, reverting to German, which her caregivers don’t speak.
Oh no, also this is interesting to me. My father spoke some Spanish, however, because his caregivers spoke Spanish he began speaking it more. A few times, only in his home, when he wasn't well he spoke it to me. It was frustrating as I didn't know what he was saying.