Systems contributing to balance disorders in older adults.

T has been shown repeatedly that older adults show a high risk for falls and that these falls are a principal contributor to fatalities in this population (1‐4). The high risk of fatalities caused by falls in older adults has made this area of research a high priority for health care. An initial aim of this research has been to document age-related deterioration in balance control to subsequently create effective assessment and treatment programs based on these specific deficits. In this issue of The Journal of Gerontology: Medical Sciences , we have included an article by Medell and Alexander (5) that examines the correlation between falls in older adults and performance on a new clinical measure, the Rapid Step Test. They show that this measure of a protective balance response is strongly related to underlying balance impairment in older adults. It is just this type of research, which combines knowledge of research on balance impairments in older adults with the creation and testing of new clinical tools for assessing balance control, that is very important in bridging the gap between research on balance in older adults and its application to clinical practice. During the early years of research on balance function in the older adult, balance was assessed both in the clinic and in the research lab using global measures of balance abilities, such as total body sway (6) and the measurement of reflex function (7). Early research exploring balance changes in older adults by Sheldon (6) examined the degree to which subjects in age groups from 6 years through 80 years swayed during quiet stance. Sheldon used a very simple technique for measuring global body sway that he could take into institutional settings. He devised a triangular metal frame with u-shaped pads that fit over the shoulders of the subject. He placed a pencil at the apex of the triangle. The pencil marked a subject’s sway on graph paper that was placed right below the pencil. Using this technique of measuring global body sway, he observed that subjects at both ends of the age spectrum (6‐ 14 years and 50‐80 years) had greater difficulty in minimizing sway during quiet stance than those in the midrange of the age spectrum. During the last 15 years, stabilometry or static force plate measures of center of foot pressure (COP) have become much more popular as measures of stability. Toupet and colleagues (8) tested 500 adults, ranging in age from 40 to 80 years, and found that postural sway (COP) increased with each decade of life, with the highest levels of spontaneous movement found in 80 year olds. A separate study has shown that sway velocity of a similar group of older subjects was significantly greater than in young adults (9). In addition, Fernie and colleagues (10) examined both sway amplitude and velocity during quiet stance in a population of institutionalized elderly persons and determined that sway velocity (but not amplitude) was significantly greater for those who fell one or more times in a year than for those who had not fallen. This implies that, in certain populations, velocity of sway may be more sensitive to balance problems than absolute sway. Patla and colleagues (11) and others make the point that measures of spontaneous sway during normal quiet stance are not necessarily appropriate measures of balance dyscontrol,