What defines primary aging?

The definition of primary aging focuses on the natural and inevitable physical changes that occur in the body as we grow older, independent of environmental factors or personal choices. This type of aging encompasses biological processes that affect everyone, such as decreases in muscle mass, skin elasticity, and organ function. These changes are a normal part of the aging process and occur regardless of an individual's lifestyle or health status.

In contrast, other options relate to influences that are not inherently tied to the biological aging process, such as lifestyle choices that can lead to various health issues or changes in abilities that stem from illness. Therefore, understanding primary aging as purely the natural progression of aging helps differentiate it from secondary aging, which is influenced more heavily by disease and environment.