Exercise as it relates to Disease/Aerobic Exercise in Parkinson's Disease: does it slow the decline?

This Wikibooks page is an analysis and fact sheet of the Journal article "Enhancing both motor and cognitive functioning in Parkinson’s disease: Aerobic exercise as a rehabilitative intervention" by Duchesne et al. (2015)

What is the background to this research?
What is Parkinson's Disease?

Parkinson’s Disease (PD) is a progressive, degenerative neurological condition that can affect a person’s control over their body. PD results from a loss of cells in the substantia niagra of the basal ganglia, a region of the brain involved in coordinating motor (movement). PD is characterised by both motor and non-motor symptoms that become more severe as the condition progresses. These symptoms are summarised in figure 1.

Statistics

A recent study has quantified the scale of PD, describing following:
 * PD is the 2nd most common neurodegenerative disorder in Australia
 * Affects 1 in every 350 people, including 1 in 100 people over 75 years old.
 * PD is growing at an increasing rate of 17% over the last 6 years
 * 20 % of people affected are of working age
 * PD costs the Australian economy $775 million a year
 * Costs have increased 48% over the last 6 years
 * Including an estimated burden of disease cost of $7.6 billion
 * Once diagnosed with PD life expectancy is 12 years
 * Every year nearly 50,000 years of healthy life are lost to PD

Exercise and Parkinson's Disease

Although PD currently has no cure, it has been shown that exercise is an effective intervention to improve function and slow down the progression of symptoms. However, this research is primarily focused on addressing motor impairments, with little known of the effect of exercise on executive functioning. Since most of our daily living activities involve the coordination of both cognitive and motor functions (eg. cooking and dressing), it is functional important that interventions also target non-motor impairments to enhance quality of life in PD. This research aimed to extend understanding in this area by investigating the affect aerobic exercise training has on cognition and motor learning in a PD population.

Where is the research from?
This study was undertaken in the following research centres and university departments:
 * Academic Geriatrics Research Center of the Institute of Montreal, Montreal, Canada
 * Functional Neuroimaging Unit, Montreal, Canada
 * Montréal University, Montréal, Canada
 * Department of Psychology
 * Department of Psychiatry
 * Centre for Research in Aging, Montréal, Canada
 * Movement Disorder Clinic, Montréal, Canada
 * Ghent University, Ghent, Belgium
 * Department of Movement and Sport Sciences
 * Department of Experimental Psychology
 * Concordia University, Montréal, Canada
 * Perform centre

What kind of research was this?
This study was a controlled, parallel trial of repeat measures design. This design aims to allow a focus population to be compared to a control group to discover whether they respond differently to the same conditions. This type of research is rated a level III-2 on the NHMRC evidence hierarchy scale. It is not rated higher as it lacks randomisation which would help limit allocation bias.

What did the research involve?
There was a total of 39 participants included in this study which were split into two groups including: Both Groups underwent examination to determine their baseline characteristics of aerobic capacity (VO2 max), cognition (inhibition & flexibility) and motor sequence learning (MSL). Both groups then participated in a 3-month, supervised aerobic exercise training (AET) regime of three x one hourly recumbent bike sessions per week. The characteristics were then retested and statistically analysed for significance. See figure 2 for a summary of this section.
 * 19 PD participants
 * 20 healthy controls (HC).

There were however limitations in this design:
 * Participants and therapists were not blinded. Blinding nullifies preconceived views of subjects, so clinicians cannot systematically bias the assessment of outcomes
 * Only included PD participants who had the lowest rating for impairments (Hoen and Yahr scale of 1-2), and were cognitively intact, making results less generalizable to larger PD populations.
 * Control group was a healthy population. A PD control group would be more similar at baseline, helping reduce confounding factors that could influence the results.

What were the basic results?
The results of this study are presented without bias from the authors, showing the effect of AET on both PD and healthy populations. No significant differences were found between the PD group and the HC’s for all characteristics. There was however a significant difference for both groups individually in pre and post testing for: However, there was no significant difference found in the flexibility component of cognitive testing.
 * VO2 Max
 * Aerobic capacity increased 11% for both PD and HC groups
 * Cognitive values
 * Decreased time and increased accuracy when completing inhibition component
 * Motor sequence learning
 * Improved speed of movement execution
 * Reduction in reaction time between sequential and random movements

How did the researchers interpret the results?
The researchers’ interpretation was that AET may improve or restore cognitive and motor functions in PD. AET had a similar effect on components of cognition, motor sequence learning and aerobic capacity in a PD population as it did in the HC. The researchers extrapolate this to suggest that AET-related improvements seen in the cognitively intact early PD could be based on similar neurophysiological mechanisms as those described in healthy older adults.

What conclusions should be taken away from this research?
This paper has highlighted an area of research that needs to be further explored to help address PD’s non-motor impairments. This study is the first to provide evidence that cognitively unimpaired PD individuals benefit from AET to the same extent, and in a similar manner, as the matched healthy controls. This merits further investigation, increasing understanding in what is a mostly untested and unproven area of research.

What are the implications of this research?
This research has successfully identified that there is a positive link between AET and cognition and MSL in mild, early PD. An AET intervention should therefore be considered as an alternative to current pharmacological interventions in combating the progression of cognitive and motor learning decline that occurs in PD. This research therefore has direct clinical implications for the management of individuals with PD.