Risk of falling: predictors based on reduced strength in persons previously affected by polio.

Abstract

To examine the contributions of sensorimotor factors to postural control and falling in people with prior polio and to determine whether these contributions differ from those found in normal populations. Survey and case-control study. A falls and balance laboratory in Australia. Forty persons with prior polio (age range, 28-71 y) and 38 age- and sex-matched control subjects. Not applicable. Lower-limb muscle strength, sway, vision, lower-limb sensation, reaction time, foot-tapping speed, and falls. Compared with the control subjects, the prior polio subjects performed similarly in sensory tests but worse in tests that involved a motor component. Within the prior polio group, lower-limb strength was strongly associated with postural sway on a compliant surface and explained more of the variance in sway than in control subjects. Prior polio subjects who fell multiple times had reduced lower-limb strength, slower reaction time, lower foot-tapping speed, and increased sway compared with those who fell less often. However, the rate of decline in lower-limb strength within the prior polio group did not exceed normal, age-related changes. This investigation of prior polio subjects provides an appropriate model for studying muscle weakness as a falls risk factor. Weakness was directly associated with falls, and had an indirect effect mediated through increased sway.