Humans stand apart from other animals in our understanding of life’s course. We are aware of its ultimate end and of the various ways aging may affect us along the way.

No doubt about it, aging is accompanied by changes in our function and form. Research has characterized in great detail the changes in function and anatomy associated with aging. 

Yet, reliance on the number of years lived (lifespan) to assess a person’s functional capacity is misguided and fails to capture the diversity of the elderly population. Some of us are skydiving at age 104 and others require skilled nursing care by age 65. What explains this wide variation in health outcomes?

Biological age, the number of years lived, is an inadequate measure of functional capacity or health status. It provides little data about a person’s “healthspan,” or how we have weathered the aging process. Some are hardy at 90 and others are frail before qualifying for Medicare.

Frailty is defined by geriatricians as a biologic syndrome resulting in decreased resistance to stressors (e.g. hospitalization for any serious condition) and the loss of reserves to mount a response able to challenge a threat and return to a prior state of health. Those caring for frail elderly folks are surely familiar with the effect on elderly patients or family members discharged to home following treatment for a serious illness. 

Frailty is not disability or comorbidity (when a patient has two or more diseases), but there is significant overlap of these conditions. Disability and comorbidity heighten risk of frailty and the risk of further decline in health status. 

Advancing age increases the prevalence of frailty from 7 percent in otherwise healthy persons over 65 to 30 percent in those over 80. 

Higher rates of frailty are associated with being African-American, having a low level of education, low income and poor health status.

Gerontologists and geriatricians agree that frailty presents a risk to the health of the general population. Diminished body bulk, strength and mobility are documented in cases of Alzheimer’s disease (AD) before the onset of cognitive changes typical of dementia. 

One recent study of the brain tissue of deceased participants in two large studies of aging and cognitive impairment revealed the microscopic changes typically associated with AD, Lewy body disease and vascular disease in 40 percent of subjects who experienced cognitive impairment. 

However, the remaining 60 percent studied had none of the microscopic changes, suggesting that other undefined brain processes, perhaps linked to frailty, lead to dementia. 

The possible linkage of cognitive loss and frailty provides a rationale for screening for cognitive function and frailty simultaneously. This has led to the term “cognitive frailty” and the initiation of the search for specific brain processes to explain the link. 

While it may not be rocket science, this search for the cause of dementia and other geriatric syndromes presents an equally daunting challenge.

Screening healthy individuals for the risk of frailty is now a recommended part of a program of primary prevention—closing the barn door before all hell breaks out. The hoped-for goal of screening is to initiate early intervention that could prevent or delay the onset of disability and comorbidity. 

Chances are you’ve been screened if you have had a recent “wellness visit” and have been asked about falls at home, to remember three random words or to draw a clock face.

Below is an established screening tool clinicians may use to define frailty. A combination of any three or more of the signs listed provides a clinical definition of frailty:

More than 10 pounds of unintended weight loss

Self-reported exhaustion (low endurance)

Decreased grip strength

Slowness

Low physical activity

A person’s chronological age provides as little information about functional capacity as the odometer of a car. Aging is not monolithic, yet unfortunately the number of years lived can take precedence over many other attributes a person may possess. 

The prevalence of frailty and dementia increases as we age, but these complex and serious conditions cannot be attributed solely to age. New understanding of brain and physical function could improve early detection and intervention to lessen the social and personal burden of frailty and cognitive impairment.