Postural instability during reaching tasks in Parkinson's disease.

BACKGROUND AND PURPOSE Reaching, like turning and rising from sitting, is an activity commonly associated with falls by people with Parkinson's disease. We set out to: (a) identify how people with moderate and severe Parkinson's disease performed high and low reaches and (b) to explore in detail the standard functional reach (functional reach) test and the fall histories of those who appeared unstable when reaching. METHOD In this cross-sectional study, people with moderate or severe Parkinson's disease (Hoehn and Yahr Grade III or IV) were video-recorded at home, reaching above shoulder height and below knee level. Blinded observers rated stability, alignment, foot position, floor contact, use of support and reach type. Functional reach was also measured and participants were interviewed about falls. RESULTS Of 51 participants, 33 (65%) had moderate Parkinson's disease and 18 (35%) severe. A greater proportion of the latter used support when reaching high (p = 0.029) and aligned forward when reaching low (p = 0.015); otherwise, strategies were similar across groups. Six people (all with severe Parkinson's disease) appeared unstable when reaching: they had a shorter functional reach than the others (median 10 cm versus 18 cm; p = 0.042) and had fallen frequently (median five falls in a year), although rarely when reaching. CONCLUSIONS Reaching tasks challenge postural stability in severe Parkinson's disease. People who appear unstable when reaching are likely to be repeat-fallers and at risk of further falls during more demanding activities. Research should address whether discouraging potentially destabilizing manoeuvres (such as squatting and toe-standing) and promoting safety-enhancing strategies (such as using support and facing forward), with or without balance retraining, reduces the risk of falling among people with severe Parkinson's disease.