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Risk of falling: predictors based on reduced strength in persons previously affected by polio
Stephen R Lord1, Gabrielle M Allen, Philippa Williams
1Prince of Wales Medical Research Institute, Randwick, Sydney, NSW, Australia. s.lord@unsw.edu.au
Objectives:
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.
Design:
Survey and case-control study.
Setting:
A falls and balance laboratory in Australia.
Participants:
Forty persons with prior polio (age range, 28-71 y) and 38 age- and sex-matched control subjects.
Interventions:
Not applicable.
Main Outcome Measures:
Lower-limb muscle strength, sway, vision, lower-limb sensation, reaction time, foot-tapping speed, and falls.
Results:
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.
Conclusions:
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.