The slowly progressive degenerative changes seen with advanced age, often with the loss of muscle and subcutaneous tissues and the shrinkage of other organs: A dynamic field of study in gerontology is senile involution which involves research about unpleasant aging changes; among them, aches and pains; decreased vigor, healing ability, sensory acuity, muscle tone, bone density; memory deficits; wrinkles; loss of beauty, friends, family, and independence; increased reliance on doctors and pills; and social isolation.