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

Baer, Michael, PT, DPT; Klemetson, Bradley, PT, DPT; Scott, Diana, PT, DPT; Murtishaw, Andrew, S., MA, PhD(c); Navalta, James, W., PhD; Kinney, Jefferson, W., PhD; Landers, Merrill, R., PT, DPT, PhD, OCS

Journal of Neurologic Physical Therapy: April 2018 - Volume 42 - Issue 2 - p 61–71
doi: 10.1097/NPT.0000000000000213
Research Articles

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.

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Spring Valley Hospital, Las Vegas, Nevada (M.B.); Meier and Marsh Professional Therapies, Tooele, Utah (B.K.); Centennial Hills Hospital, Las Vegas, Nevada (D.S.); and Departments of Psychology (A.S.M., J.W.K.), Kinesiology (J.W.N.), and Physical Therapy (M.R.L.), University of Nevada, Las Vegas.

Correspondence: Merrill R. Landers, PT, DPT, PhD, OCS, Department of Physical Therapy, University of Nevada, Las Vegas, 4505 Maryland Pkwy, Box 453029, Las Vegas, NV 89154 (

Presented at: Baer M, Klemetson B, Scott D, Navalta J, Murtishaw A, Kinney J, Landers MR. The effects of fatigue on balance in individuals with Parkinson's disease: influence of medication and brain-derived neurotrophic factor genotype. APTA Combined Sections Meeting, San Antonio, Texas, February 15-18, 2017.

Research reported in this publication was supported by a University of Nevada, Las Vegas, Student Opportunity Research Award and an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number 5P20GM109025.

The authors declare no conflict of interest.

Supplemental digital content is available for this article. Direct URL citation appears in the printed text and is provided in the HTML and PDF versions of this article on the journal's Web site (

© 2018 Academy of Neurologic Physical Therapy, APTA