"In the Middle Ages, everyone was middle-aged!" Umm, no.
As I noted in my earlier post on medieval life expectancy, the "life span" then was the same as it is now. That is, although the average age a person might reach, barring disease and disaster, before major body parts started wearing out was the same then as now, in practice most people in the Middle Ages would not make it to the age of 70, 80, or more that modern actuarial tables suggest. A lack of modern medicine, malnutrition, and rough living would do in a lot of people in their 50s.
But some people certainly grew old, even if "old" kicked in earlier for them than it does for us. And there are documented cases of rare people making it past 100--one is Saint Anthony, founder of monasticism in Egypt during late antiquity.
Old people were revered for their wisdom in the Middle Ages. Leaders like bishops and abbots were assumed to hold their office for life, rather than being pushed out at 65. Medieval old people were not put out on the ice floe! In practice, bishops and abbots might retire if they felt their strength was failing, but they rarely lived more than another year or so, not enjoying any "golden years" retirement.
Among the peasants, everyone worked until they physically could not any more, at which point they transitioned into being the voice of wisdom, telling their children all they had learned in many years of experience, whether the next generation wanted to listen or not.
Among the aristocracy, heirs waiting to inherit might encourage their parents to retire to a monastery. In practice, aristocratic women were much more likely to do so than aristocratic men. If widowed in their 40s, having seen their children more or less grow up, they might decide that they had had enough of a world of men and go off to be nuns. These widows were very often persuaded to become an abbess, because of their administrative experience.
In other cases, widows stayed in the world. One Burgundian countess in the thirteenth century survived both her husbands, argued with the new bishop of Auxerre who thought she ought to help carry him in procession on the day he was consecrated, and arranged the marriages of her children, grandchildren, and great-grandchildren.
In the modern West, most older people wear glasses, and some have had cataract surgery. Medieval people without good eyesight would just have had to grope along. (I myself would have been blind as a bat.) Eyeglasses first appeared in the fourteenth century, mostly for reading and very expensive, and cataract surgery only came into its own in the 1960s.
Few old people would have lived by themselves, because children did not move far away as often happens in modern America. As they became less able to take care of themselves, their families assisted them. Most would have been carried off by disease (such as pneumonia) or infection long before memory issues became much of a problem.
Many people now draw up living wills, saying that they don't want to be kept alive by machines and feeding tubes. This would not have been a concern in the Middle Ages.