The attention-bait of the movie aside, I think when talking about the challenges with an aging population, it's more useful to understand what the "decay curve"

The attention-bait of the movie aside, I think when talking about the challenges with an aging population, it's more useful to understand what the "decay curve" (not trying to make a pun, I'm thinking of capacitor discharge) looks like. If Japan has a life expectancy of 87/81, are people mostly unable to care for themselves and others for the last many years of that, or do they mostly stay healthy and vigorous until near the end. Is there a reason healthy 75 year olds can't take part in caring for the infirm?