Physical Strength Predicts Mortality

Aging gracefully is a challenge for all who are fortunate enough to be given the privilege of growing old. If there was a secret to staying strong and avoiding death as long as possible, someone would have surely discovered it by now. While the secret to successful aging might still elude researchers, new evidence suggests that clinicians can, at least, predict patients that will stay stronger longer.

A new study published in the British Medical Journal (BMJ) is a review and meta-analysis of 33 observational studies that evaluated the association between objective measures of physical capabilities and mortality. Grip strength was the most common measurement of physical capability, recorded in 23 of the studies, but walking speed, chair rising speed, and standing balance were also measured in several studies. Overall, poor performance on any of the 4 physical tests was associated with higher all-cause mortality. For example, participants with the lowest recorded grip strength were 1.67 times more likely to die from all-cause mortality than those with the highest grip strength, after adjustment for confounding factors. Similarly, participants with the slowest walking speed experienced a near 3-fold risk of death compared to those with the fastest walking speed.

A majority of these studies included in the BMJ analysis were conducted in people over 70 years of age. However, 5 studies evaluated grip strength in people under age 60. Across all ages, poor physical performance was associated with increased mortality. All participants were community-dwelling adults.

A similar analysis conducted by the same authors as the BMJ study compared the same objective measurements of physical performance to health status. They concluded that poor grip strength and slow walking speed were associated with an increased fracture risk and increased cognitive decline, although confounding factors may have played a role in these associations.

The BMJ study provides potentially useful markers for identifying older people at higher risk of death, but the broader question surrounds how to develop and maintain physical capabilities and strength in older age. Frailty as a component of aging describes a syndrome of global impairment and decreased physiologic reserves and overlaps with the metrics evaluated by the BMJ authors. Frailty leads to increased vulnerability, decreased tolerance for internal and external stressors, and an inability to maintain physiologic and psychosocial equilibrium. Frailty, as a clinical syndrome, is characterized by low physical activity, low muscle strength, increased fatigue, slowness of gait, and weight loss, and it is associated with adverse health outcomes, including dependency, disability, hospitalization, institutionalization, and mortality. The ambiguity of the definition and consequences of frailty in the elderly allow the clinical symptoms to be explained by comorbid conditions, nutritional deficiencies, overall deconditioning, and a host of non-descript balance and motor disorders, as well as hormonal imbalances and immune and inflammatory status. Still, elderly people who are classified as “frail” experience a significantly higher risk of falls, decreased mobility, disability, hospitalization, and death, after accounting for other confounding factors.

Related research indicates that cognitive and physical markers of physical performance and frailty are evident as early as childhood. Men and women with the highest cognitive performance and slowest memory decline throughout life (measured from adolescence to adulthood) perform better on tests of standing balance and chair rising speed. Additionally, children who performed better at milestone attainment in childhood, cognitive ability, and motor coordination showed better physical performance and muscular strength later in life. Thus, it seems that healthy living in later life begins in childhood.

Growing old is not for the faint of heart, or body, and there may never be an answer to the ever-elusive question of how to travel through life with a strong body and mind. But now, clinicians can quantify physical strength related to health and mortality risk and identify those who can make medical and lifestyle changes to increase their chance of growing old gracefully.

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