aging

Table of Contents

Introduction
Biological theories of aging
- Genetic theories
- Nongenetic theories
  - Wear-and-tear theory
  - Cross-linking theory
  - Autoimmune theory
  - theory
  - Oxidative damage theory
  - Psychosociological theory
Natural history of aging
- Reproduction and aging
- Species differences in longevity and aging
- The inheritance of longevity
Senescence in mammals
- Changes in body composition, metabolism, and activity
- Changes in structural tissues
- Tissue cell loss and replacement
- Mammalian cell cultures
- Changes in tissue and cell morphology
Aging at the molecular and cellular levels
- Aging of genetic information systems
- Aging of the immune system
- Aging of neural and endocrine systems
Internal and external causes of aging
- External environmental agents
  - Ionizing radiation
  - Temperature
  - Physical wear of nonrenewable structures
  - Infectious disease and nutrition
- Internal environment: consequences of metabolism
Anti-aging and longevity research
- Antioxidants
- Calorie restriction and longevity
- Sirtuins
- Rapamycin
- Stem cells
- Genetics and life span

References & Edit History Quick Facts & Related Topics

Images & Videos

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For Students

aging summary

aging

life process

Also known as: ageing

Written by Petra Simic, Leonard P. Guarente•All

Fact-checked by The Editors of Encyclopaedia Britannica

Last Updated: Jan 5, 2025 • Article History

Key People:: Bruce Ames; Jack W. Szostak; Elizabeth Blackburn; Carol W. Greider; Lillien Jane Martin

Related Topics:: human aging; menopause; old age; middle age; crow’s feet

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News •

Aging may change some brain cells more than others • Jan. 2, 2025, 10:01 PM ET (National Institutes of Health (NIH) (.gov))

Immunocompromised adults show weaker response to RSV vaccines • Dec. 30, 2024, 9:51 PM ET (News-Medical)

aging, progressive physiological changes in an organism that lead to senescence, or a decline of biological functions and of the organism’s ability to adapt to metabolic stress. Aging takes place in a cell, an organ, or the total organism with the passage of time. It is a process that goes on over the entire adult life span of any living thing. Gerontology, the study of the aging process, is devoted to the understanding and control of all factors contributing to the finitude of individual life. It is not concerned exclusively with debility, which looms so large in human experience, but ...(100 of 9184 words)

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