Clinical balance scales indicate worse postural control in people with Parkinson's disease who exhibit freezing of gait compared to those who do not: A meta-analysis

Postural instability and freezing of gait (FOG) are key features of Parkinson's disease (PD) that are closely related to falls. Uncovering the postural control differences between individuals with and without FOG contributes to our understanding of the relationship between these phenomena. The objective of this meta-analysis was to investigate whether postural control deficits, as detected by clinical balance scales, were more apparent in FOG+ compared to FOG−. Furthermore, we aimed to identify whether different scales were equally sensitive to detect postural control deficits and whether medication affected postural control differentially in each subgroup. Relevant articles were identified via five electronic databases. We performed a meta-analysis on nine studies which reported clinical balance scale scores in 249 freezers and 321 non-freezers. Methodological analysis showed that in 5/9 studies disease duration differed between subgroups. Despite this drawback, postural control was found to be significantly worse in FOG+ compared to FOG−. All included clinical balance scales were found to be sufficiently sensitive to detect the postural control differences. Levodopa did not differentially affect postural control (p = 0.21), as in both medication states FOG+ had worse postural stability than FOG−. However, this finding warrants a cautious interpretation given the limitations of the studies included. From subscore analysis, we found that reactive and dynamic postural control were the most affected postural control systems in FOG+. We conclude that our findings provide important evidence for pronounced postural instability in individuals with FOG, which can be easily picked up with clinical evaluation tools. Posturographic measures in well-matched subgroups are needed to highlight the exact nature of these deficits.