Physical Frailty: A Biological Marker of Aging?
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EDITORIAL PHYSICAL FRAILTY: A BIOLOGICAL MARKER OF AGING? J.E. MORLEY Division of Geriatric Medicine, Saint Louis University School of Medicine, St. Louis, Missouri, USA. Corresponding author: John E. Morley, MB, BCh, Division of Geriatric Medicine, Saint Louis University, SLUCare Academic Pavilion, Section 2500, 1008 S. Spring Ave., 2nd Floor, St. Louis, MO 63110, Email: [email protected], Twitter: @drjohnmorley
Key words: Physical frailty, biological marker, intrinsic capacity.
Intrinsic capacity is defined as the resilience that an individual has to overcome a variety of environmental, physical and psychological factors (1). A person’s intrinsic capacity is created by their genes and a number of life style factors, e.g., exercise and diet, health care, e.g., vaccines and environmental. Intrinsic capacity tends to peak between 30 to 40 years, after which it slowly declines (2) (Figure 1). Frailty is defined when a person declines at a more rapid rate than that normally seen with the decline in age-related intrinsic capacity. Frail persons are at a greater risk of decline when exposed to stressors (3). In modern geriatrics frailty is interpreted as being a transitional process between a resident individual and one with disability (4, 5). Physical frailty was operationalized by Fried et al (6). It was defined as fatigue, weight loss, weakness, slow walking gait and limited physical activity. It is predictive of poor outcomes when persons with disability are excluded (7). There are over 70 other definitions of frailty. The Rockwood Frailty Index is a co-morbidity index which can include disabilities and diseases (8). As such, it is more a marker of the effects of disease than a physiological marker of aging. Psychosocial frailty represents a separate form of frailty. Psychosocial frailty can represent a physiological decline, e.g., some forms of dementia or a disease process, such as depression, Lewy-Body dementia, and schizophrenia (9). Mild Cognitive Impairment (MCI) can be considered the equivalency of Fried’s (6) definition of physical frailty. In many cases there is overlap between MCI and physical frailty (10-12). Sarcopenia is a major component of physical frailty (13, 14). while loss of muscle mass and strength can be due to disease, e.g., diabetes mellitus or congestive heart failure much of sarcopenia is directly related to the aging process (primary sarcopenia) (13). A rapid screen for sarcopenia has been developed, i.e., the SARC-F (15-17). Takeda et al (18) have suggested that both physical frailty and MCI, when not directly disease related, can be considered a clinical model for geroscience. Numerous senolytics and other age-delaying drugs are being developed in animal models (19). While most of these drugs are not yet ready for prime time, an exception is metformin which has been successfully used to treat diabetes mellitus (20). Epidemiological evidence strongly suggests that it delays the onset of dementia (21). Studies in Received October 19, 2020 Accepted for publication October 20, 2020
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