Large trials could help assess impact of exercise in Parkinson’s

Evidence from new study hints higher intensity training may have benefit

Lindsey Shapiro, PhD avatar

by Lindsey Shapiro, PhD |

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A new review study found limited evidence that exercise may be beneficial in slowing Parkinson’s disease progression, as assessed by behavioral, neurochemical, and imaging measures.

Yet no particular exercise type emerged as superior to the others for Parkinson’s patients, although evidence hinted that a higher intensity training with more cognitive involvement could be of benefit.

“Exercise may slightly improve potential indicators of disease severity and possibly slow down disease progression in PD [Parkinson’s],” the researchers wrote.

Further research — including large clinical trials — is still needed, according to the team, with a goal to “determine differential effects based on exercise type, exercise dose and disease severity.”

The study, “Does Exercise Attenuate Disease Progression in People With Parkinson’s Disease? A Systematic Review With Meta-Analyses,” was published in Neurorehabilitation and Neural Repair.

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A large body of evidence indicates that regular exercise — typically targeted as at least 2.5 hours per week — is beneficial for people with Parkinson’s and other neurodegenerative disorders. Such workout programs may help patients maintain their functional independence and ease symptoms.

In contrast to available Parkinson’s medications, which can ease symptoms but don’t overall alter the disorder’s progression, it’s been suggested that exercise could have a disease-modifying effect. Specifically, it’s thought that regular exercise may promote a process called neuroplasticity — where the brain re-wires itself in response to new inputs.

Still, studies that have evaluated the benefits of exercise haven’t been consistent in the type of exercise or clinical outcomes evaluated. That means that information on the forms of exercise — and how much of it — that might be able to slow Parkinson’s progression is not well-established.

To find out, the researchers conducted a systematic review of previously published clinical trials that looked at exercise in Parkinson’s, focusing particularly on outcome measures that could reflect a slowing of disease progression rather than only symptom suppression.

The analysis ultimately included 4o trials which cumulatively involved 2,104 Parkinson’s patients. All were randomized and controlled. Overall, participants had mild to moderate Parkinson’s with a mean disease duration of 6.1 years.

Exercise types included aerobic or cardio, strength, balance, dance, aquatic, or a combination. The exercise of interest was compared with either a no-exercise control or another form of exercise. The trials varied widely in terms of exercise duration, intensity, and outcome measures, the team noted.

A total of six trials and seven analyses evaluated Movement Disorder Society-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) motor scores during off periods as an indicator of Parkinson’s progression.

Off periods are those in between doses of standard Parkinson’s medications during which symptoms may re-emerge. The scientists noted that measuring motor scores during these periods may “more closely reflect disease severity” without the confounding effects of medication.

A pooled analysis of these studies indicated a possible medium beneficial effect of exercise on MDS-UPDRS motor scores during off periods relative to a control group. However, given the low number of studies, “this result needs to be interpreted with caution,” the researchers noted.

A pooled analysis of studies that reported patients’ blood levels of brain-derived neurotrophic factor (BDNF) with exercise similarly found some evidence that BDNF may increase with exercise, but could not be interpreted with certainty. BDNF is a brain signaling molecule thought to promote the survival and function of the dopamine-producing nerve cells that are progressively lost in Parkinson’s.

Exercise was not overall linked to reductions in inflammation or oxidative stress, a type of cellular damage implicated in Parkinson’s.

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Larger, more specific studies needed on Parkinson’s and exercise

Findings from trials that reported MRI outcomes generally found that exercise was associated with more normalized brain activation and connectivity, which could reflect underlying neuroplasticity.

Some studies did also indicate that exercise could increase dopamine receptor binding, a finding that could indicate stronger dopamine signaling in the brain.

While the possible benefits of exercise over a control were observed, additional analyses did not reveal that any particular exercise to be most beneficial.

“Overall, no one type of exercise was found to be consistently superior to another in attenuating [Parkinson’s] progression across the various outcome measures investigated,” the researchers wrote, noting that data for each exercise type were limited and variable.

Some evidence did indicate that exercising at a higher intensity or with greater cognitive engagement may be most beneficial on disease progression, but these findings were not consistent.

In all, the study did not identify a particular type of exercise that could most benefit Parkinson’s patients, but did identify outcome measures that could be useful for monitoring Parkinson’s progression in future studies.

Future [clinical trials] should include participants from only 1 disease severity stage, or include large samples ensuring sufficient participants in each disease stage and report results for each disease stage, to enable subgroup analysis.

Inclusion of measures such as MDS-UPDRS off scores, BDNF, and dopamine receptor binding, “will enable future trials to better elucidate any benefits of exercise for attenuating [Parkinson’s] progression and conduct of larger, more robust meta-analyses,” the team concluded.

The researchers did recommend that further studies involve more patients and be more specific, noting that the work reviewed here involved a “large number of heterogenous outcomes examined by very few trials, many of which had small samples.”

“Future [clinical trials] should include participants from only 1 disease severity stage, or include large samples ensuring sufficient participants in each disease stage and report results for each disease stage, to enable subgroup analysis,” the  team wrote.