Table 2.

Electronic search keywords

Category	Keywords	Additional common words (in abstract or title)	Additional parameters based on most common non-relevant hits
Population	Parkinson’s disease OR human OR patients OR aged	Subject* OR Participant*
Intervention	Therapy OR Disease Progression	Neuroprotect* OR Delay* OR Improv* OR Treatment
Comparator	Random allocation OR Control groups OR placebo
Outcome	Safety OR adverse	Efficacy OR benefit OR slow OR risk	NOT ‘deep brain stimulation’ NOT ‘predict* model’
Study design	Clinical trial	Study OR Phase