Originally Posted by chasm54

I agree with this and would only add that the process is not linear. Geriatricians are familiar with the fact that people's capacities don't decline gradually with age, but do so in a series of steps - they have a crisis, such as a fall or an acute illness, and although they do recover, they get back only, say, 80% of their full functionality (simplistic to reduce it to a percentage, but it illustrates the point) and then carry on at that lower level for a while, until the next crisis.