Introduction to Geriatrics

ByRichard G. Stefanacci, DO, MGH, MBA, Thomas Jefferson University, Jefferson College of Population Health
Reviewed/Revised Apr 2024
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Geriatrics refers to medical care for older adults, an age group that is not easy to define precisely. Gerontology is the study of aging, including biologic, sociologic, and psychologic changes. “Older” is preferred over "elderly," but both terms are equally imprecise. It is important to avoid terms and attitudes that suggest bias against older adults (ageism). Although there is no set age to define older age, > age 65 is often used because this is the age that determines eligibility for Medicare insurance in the United States. However, some people with medical conditions require geriatrics expertise at a younger age. For example, the Program of All-Inclusive Care for the Elderly (PACE) sets the age for eligibility beginning at 55 for people who meet the need for nursing home level of care.

The percentage of the US population that was ≥ 65 increased from 5% in 1920 to almost 17% in 2020. That percentage is projected to increase further (1).

In 2019, life expectancy at age 65 was an additional 18.2 years for men and 20.8 years for women (2). Overall, women live about 4 to 5 years longer than men (3). These differences in survival have changed little despite changes in women’s lifestyle (eg, increased smoking, increased stress) over the late 20th century and into the 21st.

General references

  1. 1. United States Census Bureau: 2020 Census: 1 in 6 people in the United States were 65 and over. 2023. Accessed 3/9/24.

  2. 2. National Center for Health Statistics: NCHS Fact Sheet. 2021. Accessed 3/9/24.

  3. 3. Thornton J: WHO report shows that women outlive men worldwide. BMJ 2019;365:l1631, 2019. doi: 10.1136/bmj.l1631 Published 05 April 2019.


Aging (ie, pure aging) refers to the inevitable, irreversible decline in organ function that occurs over time even in the absence of injury, illness, environmental risks, or poor lifestyle choices (eg, unhealthy diet, lack of exercise, substance abuse). Initially, the changes in organ function (see table Selected Physiologic Age-Related Changes) do not affect baseline function; the first manifestations are a reduced capacity of each organ to maintain homeostasis under stress (eg, illness, injury). The cardiovascular, renal, and central nervous systems are usually the most vulnerable (the weakest links).

Diseases interact with pure aging effects to cause geriatric-specific complications (now referred to as geriatric syndromes), particularly in the weak-link systems—even when those organs are not the primary ones affected by a disease. Typical examples are

Aging organs are also more susceptible to injury; eg, intracranial hemorrhage is more common and is triggered by less clinically important injury in older adults.

The effects of aging must be taken into account during the diagnosis and treatment of older adults. Clinicians should not

  • Mistake pure aging for disease (eg, slow information retrieval is not dementia)

  • Mistake disease for pure aging (eg, ascribe debilitating arthritis, tremor, or dementia to old age)

  • Ignore the increased risk of adverse drug effects on weak-link systems stressed by illness

  • Forget that older adults often have multiple underlying disorders (eg, hypertension, diabetes, atherosclerosis) that accelerate the potential for harm

In addition, clinicians should be alert for diseases and problems that are much more common among older adults (eg, heart failure with reduced ejection fraction, Alzheimer disease, incontinence, atrial fibrillation). This approach enables clinicians to better understand and manage the complexity of the diseases that often coexist in older patients. Understanding the physical changes and geriatric-specific manifestations of disease that accompany advancing age is important to avoid the negative and prejudicial stereotypes about older adults that characterize ageism and can negatively affect patient care and quality of life.

Ageism refers to prejudice against people of older age. Similar to other forms of prejudice (eg, racial, ethnic), ageism is based on negative misconceptions and stereotypes and may be conscious or unconscious, overt or subtle. Unlike many other forms of prejudice, ageism is rarely intentionally malicious but nonetheless can cause emotional distress and has adverse practical consequences (eg, being encouraged to retire from work, not invited to participate in groups or committees). Health care practitioners effectuate age bias by not offering a treatment to an older adult based simply on their age rather than on factors such as expected life expectancy, quality of life, and patient preference.

More Information

The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

  1. Program of All-Inclusive Care for the Elderly (PACE): This web site provides information about access to PACE benefits for certain frail, community-dwelling older adults Most are eligible for both Medicare and Medicaid benefits. Links to additional information are also provided.

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