Definitions of Gerontology, Geriatrics, Ageing, and Life Expectancy

Gerontology is the interdisciplinary scientific study of the ageing process, encompassing biological, psychological, and social dimensions of growing older (Stieglitz, 1940). As Stieglitz articulated, gerontology is "the science of aging" concerned with "all the aspects of aging" (p. 1). All living matter ages from the moment of conception until death, making ageing a fundamental biological phenomenon that is part of living itself (Saxon et al., 2020).

Definitions: Gerontology, Geriatrics, Ageing, and Life Expectancy

Distinguishing Gerontology from Geriatrics

A critical distinction exists between gerontology and geriatrics. While gerontology is the study of ageing from multiple standpoints—including biology, genetics, psychology, sociology, anthropology, philosophy, history, and religion—geriatrics is the branch of medicine that treats the conditions and diseases associated with ageing and old age (Hooyman & Kawamoto, 2018). Geriatrics refers specifically to healthcare delivery for the elderly, whereas gerontology encompasses all aspects of the ageing process (Cavanaugh & Blanchard-Fields, 2019).

Table 1.1: Distinguishing Gerontology and Geriatrics

Aspect	Gerontology	Geriatrics
Definition	The scientific study of the ageing process (Stieglitz, 1940)	The branch of medicine treating conditions associated with ageing (Nascher, 1909)
Focus	Biological, psychological, and social aspects of ageing	Diagnosis, treatment, and management of diseases in older adults
Scope	Interdisciplinary (biology, psychology, sociology, anthropology, etc.)	Medical (clinical practice, pharmacology, geriatric syndromes)
Orientation	Research, theory, and policy	Clinical practice and patient care
Key Question	How and why do we age?	How do we treat age-related conditions?

*Note: Adapted from Cavanaugh and Blanchard-Fields (2019) and Hooyman and Kawamoto (2018)*

Understanding Ageing

Ageing must be understood as a process, distinct from the aged who are the consequences of this process. The study of ageing involves examining both evolutional or growth phenomena and involutional processes (Hayflick, 1996). Modern gerontology has shifted away from pathologising ageing toward a lifespan perspective that recognises ageing as part of the normal lifelong developmental trajectory (Erikson, 1980; Baltes, 1987).

Life Expectancy and Longevity

Life expectancy refers to the average duration of life for a given population, typically calculated as the average number of years a person of a given age may be expected to live (World Health Organization [WHO], 2025). Longevity (or lifespan) refers to the duration of life of an individual. Mean longevity is the average longevity of a population (Olshansky & Carnes, 2001).

The concept of healthy life expectancy (or disability-free life expectancy) measures the average time an organism is expected to live in good health, free from disability (WHO, 2020). This distinction is crucial because living longer does not necessarily mean living healthier (Crimmins et al., 2010).

Global life expectancy reached 73.5 years in 2025 (United Nations Population Fund [UNFPA], 2025). This dramatic increase represents one of the most significant achievements of modern public health. As Olshansky and Carnes (2001) note, there has been a 26-year gain in average life expectancy in approximately one century—a gain "almost equal to 5,000 previous years of human history" (p. 14).

Self-Assessment Exercise 1.1

Instructions: Reflect on the following questions and write brief responses (2-3 sentences each). Check your answers against the tips provided.

1.     Question: In your own words, explain the difference between gerontology and geriatrics. Why is this distinction important for professionals working with older adults?

2.     Question: How does the concept of "healthy life expectancy" differ from simply "life expectancy"? What implications does this distinction have for policy and practice?

3.     Question: Why is it important to distinguish between "ageing" as a process and "the aged" as people?

Answer Tips:

·        For Question 1: Gerontology is the study of ageing across multiple disciplines; geriatrics is the medical practice of treating age-related conditions (Cavanaugh & Blanchard-Fields, 2019). The distinction matters because effective work with older adults requires understanding beyond just medical treatment—social, psychological, and environmental factors are equally important (Hooyman & Kawamoto, 2018).

·        For Question 2: Life expectancy measures quantity of years; healthy life expectancy measures quality of years lived without disability (WHO, 2020). This distinction highlights that extending life is insufficient without also ensuring quality of life, guiding policies toward healthy ageing rather than merely prolonging life.

·        For Question 3: Ageing is an ongoing process that happens to all living beings; "the aged" are people who have experienced this process (Saxon et al., 2020). This distinction prevents reducing older adults to their age-related changes and reminds us to see the whole person, not just their age.