Complex sentence: People with Alzheimer's disease will ultimately not be able to perform even the simplest tasks independently; muscle mass and mobility deteriorate to the point where they are bedridden and unable to feed themselves.
Split into simpler sentences: People with Alzheimer's disease will ultimately not be able to perform even the simplest tasks independently. Muscle mass and mobility deteriorate to the point where they are bedridden, and they lose the ability to feed themselves.