[The stages of human life, the 16th century.](Author: English school - http://0rchid-thief.livejournal.com/686506.html?thread=3547306, Public domain, Link)
Each person can have a different interest in life. And in most people live their lives to the end actively and in motion. But there are also situations when a person begins to get bored with age. Why is lost or interest in life is getting smaller and smaller with every new year lived. This can happen if a person does not have an occupation that could interest him. All this comes from the fact that not everyone can be engaged in old age, because health is not the same.

But I want to draw another aspect that, in my opinion, affects the interest in life. A lot of living conditions in this world are laid mostly in childhood. And all of them are based on the fact that we begin to be interested in the world around us. We are trained, because everything is new for us in the district. And this is not only the first steps, it is the study of books and sciences, the employment of some kind of developing hobby ... All of us are fascinated and we are all interested. And so gradually, with every passing day and every year, we learn or try, something-toning and interesting. Now imagine a person in 70 years. Who will tell you that he already knows everything. We do not rarely listen to the advice of older people. Or who has already tried everything and is not interested in it already, since it does not bear in itself that effect of novelty and curiosity. All this together, plus the loss of loved ones, very often makes people bored in their last days or years. In this regard, the people of mental work are very lucky, who are able to engage in mental activity to the very last breath without difficulty and most importantly with interest. After all, mental labor implies a constant solution of riddles. But people who are no longer able to learn anything with age are forced to do all the same as their whole life. And such lessons become boring over time. And we always want novelty and surprise, just like little children ...
Something like this…

Gerontology is the study of the social, cultural, psychological, cognitive, and biological aspects of ageing. The word was coined by Ilya Ilyich Mechnikov in 1903, from the Greek γέρων, geron, "old man" and -λογία, -logia, "study of".[1] The field is distinguished from geriatrics, which is the branch of medicine that specializes in the treatment of existing disease in older adults. Gerontologists include researchers and practitioners in the fields of biology, nursing, medicine, criminology, dentistry, social work, physical and occupational therapy, psychology, psychiatry, sociology, economics, political science, architecture, geography, pharmacy, public health, housing, and anthropology.
Hooyman, N.R.; Kiyak, H.A. (2011). Social gerontology: A multidisciplinary perspective (9th ed.). Boston: Pearson Education. ISBN 0205763138.