When does human aging begin during the life span?

Human aging begins as soon as an individual reaches adulthood. It is a continuous, progressive process that occurs throughout the entire adult life span, representing a fundamental phase of human life alongside infancy, childhood, and adolescence.12

From a physiological perspective, aging involves a gradual decline in the biological functions of organs and a reduced ability to adapt to metabolic stress, eventually leading to senescence. Sociologically, this process is accompanied by shifts in behavior, social interactions, and activities. Gerontology—the study of aging—focuses on the changes that occur between the attainment of maturity and death, examining how individuals navigate new psychosocial demands and maintain their self-concept throughout these developmental stages.123