Age-Related Change in Mobility: Perspectives From Life Course Epidemiology and Geroscience

Abstract

Mobility is the most studied and most relevant physical ability affecting quality of life with strong prognostic value for disability and survival. Natural selection has built the "engine" of mobility with great robustness, redundancy, and functional reserve. Efficient patterns of mobility can be acquired during development even by children affected by severe impairments. Analogously, age-associated impairments in mobility-related physiological systems are compensated and overt limitations of mobility only occur when the severity can no longer be compensated. Mobility loss in older persons usually results from multiple impairments in the central nervous system, muscles, joints, and energetic and sensory physiological systems. Early preclinical changes in these physiological systems that precede mobility loss have been poorly studied. Peak performance, rate of decline, compensatory behaviors, or subclinical deterioration of physiological resources may cumulatively influence both timing of mobility loss and chances of recovery, but their role as risk factors has not been adequately characterized. Understanding the natural history of these early changes and intervening on them would likely be the most effective strategy to reduce the burden of disability in the population. For example, young women with low bone peak mass could be counseled to start strength resistance exercise to reduce their high risk of developing osteoporosis and fracture later in life. Expanding this approach to other physiological domains requires collecting and interpreting data from life course epidemiological studies, establishing normative measures of mobility, physical function, and physical activity, and connecting them with life course trajectories of the mobility-relevant physiological domains.

Keywords: Epidemiology; Geroscience; Life course.; Mobility.

Published by Oxford University Press on behalf of the Gerontological Society of America 2016.

Figures

Figure 1.

Average (and standard errors) annual rates of change of walking speed in men and women participants of the InCHIANTI study according to 5-year age groups at study entry. To address selective attrition, rates of change were estimated by mixed effect models with inverse probability weighting. Three different walking tasks were considered: 4-m walk at usual and fast speed and 400-m walk at fast speed. Rates of change were estimated using data from baseline and 3-, 6-, 9-, and 14-year follow-up. Rates are plotted at the lower age for the interval (eg, 20 is for participants who were 20–25 years old at study entry). Specific values plotted in this figure are reported in Supplementary Tables 1a and b. Description of the performance measures assessed in InCHIANTI and a global description of the InCHIANTI study have been reported elsewhere (134,135).

Figure 2.

Usual walking speed at different ages in Men (n = 711) and Women (n = 766) participants of the Baltimore Longitudinal Study of Aging.

Figure 3.

Hypothetical model of individual versus population trend. Trajectories a–f are from individual subjects, while the red line is the population overall trajectory. At the population level, the critical age for change appears to be around 70, but the ages when critical declines occur (as indicated by the stars) are quite variable across individuals.

Figure 4.

World record times for running 5,000 m according to age and sex.