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Multicenter Study
. 2020 Jun;35(6):969-975.
doi: 10.1002/mds.28002. Epub 2020 Mar 27.

Factor Analysis and Clustering of the Movement Disorder Society-Non-Motor Rating Scale

Pablo Martinez-Martin  1 , Jose Manuel Rojo-Abuín  2 , Daniel Weintraub  3 , Kallol Ray Chaudhuri  4 , Carmen Rodriguez-Blázquez  5 , Alexandra Rizos  4 , Anette Schrag  6
Affiliations
Multicenter Study

Factor Analysis and Clustering of the Movement Disorder Society-Non-Motor Rating Scale

Pablo Martinez-Martin et al. Mov Disord. 2020 Jun.

Abstract

Background: The primary validation of the Movement Disorder Society Non-Motor Rating Scale was recently published, but 2 important structural analyses were not included. The objective of this study was to examine the structural characteristics of the Movement Disorder Society Non-Motor Rating Scale by factor and cluster analyses.

Methods: Data came from the validation study, an international multicenter cross-sectional study of 402 Parkinson's disease patients. Demographic and clinical data, the Movement Disorder Society Non-Motor Rating Scale, and Hoehn and Yahr staging were used. Exploratory and confirmatory factor analysis and nonhierarchical cluster analysis were performed.

Results: The exploratory factor analysis showed that all 13 domains of the Movement Disorder Society Non-Motor Rating Scale, except 1, and the Non-Motor Fluctuations subscale performed as unidimensional (variance explained: 0.36, sleep and wakefulness; -0.82, orthostatic hypotension). The confirmatory factor analysis could be carried out in 9 domains and showed that 6 of them and the Non-Motor Fluctuations subscale adjusted to the model satisfactorily according to the root mean square error of approximation. Furthermore, all domains had comparative fit index values >0.95, except depression and pain (both, 0.94) and sleep and wakefulness (0.90). The Non-Motor Fluctuations subscale showed satisfactory root mean square error of approximation (0.07), but a low comparative fit index value (0.91). A 5-cluster solution, correctly classifying 96% of the cases, was found.

Conclusions: Overall, most subscales of the Movement Disorder Society Non-Motor Rating Scale are unidimensional, and although each subscale is distinct in terms of content covered, factors and clusters that are of clinical relevance are discernible and contribute to our understanding of possible nonmotor subtypes in Parkinson's disease. © 2020 International Parkinson and Movement Disorder Society.

Keywords: Nonmotor symptoms; Parkinson's disease; cluster analysis; factor analysis; rating scale.

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References

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    1. Martinez-Martin P, Schrag A, Weintraub D, et al. Pilot study of the International Parkinson and Movement Disorder Society-sponsored Non-Motor Rating Scale (MDS-NMS). Mov Disord Clin Pract 2019;6:227-234.
    1. Ray Chaudhuri K, Schrag A, Weintraub D, Rizos A, Rodriguez-Blazquez C, Mamikonyan E, et al. The Movement Disorder Society Non-Motor Rating Scale (MDS-NMS): Initial validation study. Mov Disord 2019; https://doi.org/10.1002/mds.27862.
    1. Goetz CG, Tilley BC, Shaftman SR, et al. Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS): scale presentation and clinimetric testing results. Mov Disord 2008;23:2129-2170.
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