No one, not even a spouse, is allowed to discuss your medical matters with medical personnel, to deal with insurance issues, fill a prescription or to act as your advocate without your written permission.
An accident or illness that requires assistance from others, whether temporarily or long term, can happen at ANY age.
Effective care giving requires readily available and easy to understand written information and instructions to make it easy for any number of people to lend a hand when needed.
If there is a primary care giver, it is particularly important that everything be in writing in the event something occurs that keeps them from their responsibilities for some period of time.
Putting together a written care giving plan can help to keep the elderly, the disabled, dementia patients, etc. in their homes.