Geriatrics refers to medical care for older adults, an age group that is not easy to define precisely. “Older” is preferred over "elderly," but both are equally imprecise; > 65 is the age often used, but most people do not need geriatrics expertise in their care until age 70, 75, or even 80. Gerontology is the study of aging, including biologic, sociologic, and psychologic changes.
Around the year 1900 in the US, people > 65 accounted for 4% of the population; now they account for > 14% (nearly 50 million, with a net gain of 10,000/day). In 2026, when post–World War II baby boomers begin to reach age 80, estimates suggest that > 20% (almost 80 million) will be > 65. Mean age of those > 65 is now a little more than 75, and the proportion of those > 85 is predicted to increase most rapidly.
Life expectancy is an additional 17 years at age 65 and 10 years at age 75 for men and an additional 20 years at age 65 and 13 years at age 75 for women. Overall, women live about 5 years longer than men, probably because of genetic, biologic, and environmental factors. 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.
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 delirium complicating pneumonia or urinary tract infections and the falls, dizziness, syncope, urinary incontinence, and weight loss that often accompany many minor illnesses in older adults. 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, diastolic heart failure, 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.