Successful aging: Advancing the science of physical independence in older adults

Abstract

The concept of 'successful aging' has long intrigued the scientific community. Despite this long-standing interest, a consensus definition has proven to be a difficult task, due to the inherent challenge involved in defining such a complex, multi-dimensional phenomenon. The lack of a clear set of defining characteristics for the construct of successful aging has made comparison of findings across studies difficult and has limited advances in aging research. A consensus on markers of successful aging is furthest developed is the domain of physical functioning. For example, walking speed appears to be an excellent surrogate marker of overall health and predicts the maintenance of physical independence, a cornerstone of successful aging. The purpose of the present article is to provide an overview and discussion of specific health conditions, behavioral factors, and biological mechanisms that mark declining mobility and physical function and promising interventions to counter these effects. With life expectancy continuing to increase in the United States and developed countries throughout the world, there is an increasing public health focus on the maintenance of physical independence among all older adults.

Keywords: Age; Healthspan; Longevity; Mobility; Obesity; Sarcopenia.

Figure 1

The conceptual model illustrates important factors that can affect physical function during aging and ultimately maintenance of health and independence in older adults. Biological mechanisms and behavioral factors associated with reductions in physical function are illustrated in the outer ring. Specific health conditions that contribute to reductions in mobility and physical performance during aging are displayed in the middle ring. These conditions include but are not limited to cognitive decline, dynapenia, obesity, pain, and sarcopenia. Promising interventions for enhancing mobility and physical function, which target one or more biological mechanisms, behavioral factors, or health conditions contributing to functional decline, are shown in the outer edges. The ultimate goal is maintenance of health and independence, displayed in the inner most ring, through enhancement of mobility and/or physical function. This figure is not intended to be exhaustive but rather to highlight key biological mechanisms, behavioral factors, and health conditions that can contribute to functional decline in older adults, as well as promising interventions to attenuate declines in mobility and physical function during aging. MT: Mitochondria.

Figure 2

The pathophysiology model illustrates key biological mechanisms that contribute to functional decline. Cellular mechanisms are displayed in the outer ring, tissue specific mechanisms are displayed in the next ring, and systemic mechanisms are displayed in the two inner rings.

Figure 3

The intervention model displays the effects different interventions have on biological and behavioral factors contributing to functional decline, as well as the interconnection between biological and behavioral factors with health conditions known to contribute to functional decline. Connections that have clear empirical support are displayed with a solid line, and theoretical connections are displayed with a dotted line.