Ben Best wrote an article on the mechanism of aging. Where he explains what ageing is, the causes, etc.
Aging is a syndrome of changes that are deleterious, progressive, universal and so far, irreversible.
The aging process occurs in molecules, cells and organs. The diseases of old age, such as diseases related to the heart, Alzheimer, etc, are often distinguished from ageing itself. But even if the ageing process is distinct from the diseases of ageing, it is nevertheless true that the damage associated with the ageing process increases the likelihood of old age diseases.
To read the article click here: https://www.benbest.com/lifeext/aging.html#define