DYNAMIC BALANCE IN OLDER PERSONS - EFFECTS OF REDUCED VISUAL AND PROPRIOCEPTIVE INPUT

Background. Understanding the motor and sensory contributions to balan ce function in older persons is important in order to design effective interventions to prevent falls and loss of mobility. We tested the co ntributions of visual and proprioceptive input, muscle strength, and a ge to balance performance in 110 subjects free of clinical evidence of neurologic disease (mean age 80 years).Methods. The EquiTest Sensory Organization Test was used to present sequential conditions that alter ed sensory input in a 2 (tactile/proprioceptive input) x 3 (visual inp ut) design. Center of force and shear force data were recorded from th e platform; the primary outcomes were loss of balance (LOB) and anteri or-posterior center of force (COF) displacement as a proportion of foo t length (COFD). Results. Subjects had 3.5 +/- 2.7 LOB during testing. Reduction of vision input increased the odds ratio of a LOB 5.7 fold (3.9, 8.4, 95% CI) in unstable surface conditions, but adaptation with repeated trials was substantial. The adjusted odds ratio of a LOB was 0.65 and 0.45 in the second and third trials, respectively, compared to the first. Muscle strength and age were independent predictors of L OB. Gait velocity, single stance balance, and reported difficulty with ambulation, mobility, and instrumental activities of daily living wer e also associated with LOB. Conclusions. Performance on clinical tests of strength, balance, and gait was associated with performance on a c hallenging balance test which reduced sensory input and effectiveness of motor responses. Adaptation to challenging balance conditions was s ubstantial in this group of older subjects, but was diminished in the oldest subjects.