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Effects of Fatigue on Balance in Individuals With Parkinson Disease: Influence of Medication and Brain-Derived Neurotrophic Factor Genotype

Background and Purpose: Because falls can have deleterious consequences, it is important to understand the influence of fatigue and medications on balance in persons with Parkinson disease (PD). Thus, the purpose of this study was to investigate the effects of fatigue on balance in individuals with PD. Because brain-derived neurotrophic factor (BDNF) has been shown to be related to motor performance, we also explored its role. Methods: A total of 27 individuals (age = 65.4 ± 8.1 years; males = 14, females = 13) with neurologist-diagnosed PD with 13 genotyped for BDNF as Val66Val, 11 as Val66Met, 2 as Met66Met (1 refused). Participants were tested both on and off medication, 1 week apart. On both days, they completed a pre- and posttest separated by a fatiguing condition. Factorial analyses of variance were performed for the following balance domains: (1) anticipatory postural responses; (2) adaptive postural responses; (3) dynamic balance; (4) sensory orientation; and (5) gait kinematics. For BDNF, t-tests were conducted comparing genotype for the pre-post difference scores in both the on and off medication states. Results: There were no interactions between time (pre- and postintervention) and medication for any of the domains (Ps ≥ 0.187). Participants with BDNF Met alleles were not significantly different from Val66Val participants in balance (Ps ≥ 0.111) and response to a fatiguing condition (Ps ≥ 0.070). Discussion and Conclusions: Fatigue does not appear to have a detrimental effect on balance, and there was not a differential effect of medication in individuals with PD. These results also indicate that participants with a BDNF Met allele did not have a greater decay in function after a fatiguing condition. Video Abstract available for more insights from the authors (see Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A196).