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Table 5 Outcomes and risk of bias of clinical trials on human Parkinson’s disease

From: The effects of exercise on cognition in Parkinson’s disease: a systematic review

Study Behavioral outcomes Major sources of risk of bias
Studies that specifically measured executive function (n = 4)
McKee et al. 2013 [29] • Tango improved disease severity (UPDRS-III) and spatial cognition/mental imagery (Brooks Spatial Task) more than education group, maintained gains 10–12 weeks post-intervention • Detection bias: study was underpowered (n = 23 tango, n = 8 education) to evaluate some main effects within groups, so main effect of time was evaluated
Cruise et al. 2011 [26] • Exercise improved verbal fluency and spatial working memory on Cambridge Neuropsychological Test Automated Battery • Selection bias: the control group received usual care, no control for the effect of social interaction with exercise
• Exercise was of “possible benefit” on semantic fluency and mood • Information bias: the variable intensity level of the intervention could have affected outcomes
• Exercise did not benefit spatial or pattern recognition, quality of life, had no negative impact
Ridgel et al. 2011 [28] • Time to complete Trail Making Test A & B (tests executive function) decreased after passive cycling • Selection bias: no control
• Information bias: the same test pattern was used pre- and post-intervention, although practice effects were attempted to be controlled through pre-test training with the task
• Performance improved on Trail Making Test B following passive cycling
Tanaka et al. 2009 [27] • Exercise improved executive function for “Categories Completed” (i.e., capacity for abstraction) and “Preservative Errors” (i.e., mental flexibility) on the Wisconsin Card Sorting Task • Selection bias: small sample size, no long-term follow-up, not purely randomized
•Information bias: no mention of medication administration; only one participant in the group had a heart rate monitor, so the intensity was targeted towards the group and not the individual
• No interactions for confounding variables: concentrated attention, trait or state anxiety, depression
Studies that measured unspecified aspects of cognition (n = 4)
Dos Santos Mendes et al. 2012 [25] • PD showed no deficit in learning or retention on 7/10 games, deficits related to cognitive demands of tasks • Selection bias: the baseline physical fitness of the subjects was not compared
• PD had worse performance than healthy individuals on 5 tests • Performance bias: no PD controls not performing intervention, no control for enjoyment or motivation
• PD could transfer learning to an untrained motor task at follow-up
Pompeu et al. 2012 [24] • Both groups improved UPDRS-II, MoCA and balance, no additional advantage from Wii FitTM • Information bias: the baseline physical fitness of the subjects was not compared, so potential for differences between groups
• Improved scores on Wii FitTM games, maintained at follow-up
• No differences in outcomes between groups pre- to post-intervention or in follow-up
Müller et al. 2010 [23] • Reaction time increased after rest and decreased after exercise, movement time decreased after exercise • Selection bias: no PD control group, no healthy controls
• Information bias: one-day washout period (24 hours) may not have been long enough; pilot trial
• Number of correct answers decreased after rest
• Tapping rate increased after exercise • Detection bias: unclear how reactivity was measured
• Peg insertion interval time decreased after exercise (complex movement sequences, visual and spatial cognition, sorting and planning)
Baatile et al. 2000 [22] • Improved UPDRS score (only total score significant) • Selection bias: limited sample size, no control group; pilot trial
• Improved PDQ-39 score, most improved in cognition component • Information bias: exercise intensity not standardized