Developing and validating the Japanese version of Dimensional Apathy Scale (<scp>J‐DAS</scp>)

Abstract

‘Apathy’ is defined as a syndrome of primary lack of motivation1 and is commonly observed in neurological and psychiatric disorders2 as well as in the healthy population.3 In Japan, apathy has been defined and extensively researched. Clusters of patients who exhibit a loss of motivation can be separated from vascular depression with research focusing on apathy as a construct.4 Levy and Dubois have conceptualized a neurobiological multidimensionality of apathy2 in which there is a “quantitative reduction of voluntary, goal-directed behaviors” and multidimensional apathy is recognized in the diagnostic criteria for apathy.5 Originally developed in English,6 the Dimensional Apathy Scale (DAS) quantifies apathy subtypes, which are related to different brain regions and networks, with reference to the Levy and Dubois model.2 The DAS classifies apathy as: ‘executive apathy,’ a lack of motivation for planning, organization or attention; ‘emotional apathy,’ an emotional flatness, blunting, and indifference; and ‘initiation apathy,’ a lack of motivation for self-generation of thoughts or actions. The DAS has been translated and used in various other languages, such as Italian.7 The aim of the present study was to translate and validate a Japanese version of the DAS (J-DAS) for assessing apathy subtypes. The original DAS was first translated into Japanese by Japanese collaborators (T. K., K. O., and S. Y.) and then back-translated by a third party (Text-Edit.com: www.text-edit.com/english-page/). The translated version was checked by and discussed with a coauthor (R. R.), one of the authors of the original DAS, and further revised. This procedure was iteratively completed until agreement was reached among all authors. The J-DAS can be found in Table S1. We conducted an online survey to validate the J-DAS against the Apathy Scale (AS-14),8 which is a 14-item traditional ‘one-dimensional’ apathy scale, and Beck's Depression Inventory II (BDI-II),9 a 21-item questionnaire for assessing depression. We analyzed 496 participants (mean age = 44.8 years; SD = 13.8 years; 250 female/246 male; mean years of education: 14.6, SD = 2.3) who gave informed consent and whose anonymity has been preserved (see Supplemental Information). They scored a mean of 14.6 (SD = 12.0) on the BDI-II and a mean of 17.5 (SD = 7.0) on the AS-14. On the DAS total, they scored a mean of 35.1 (SD = 6.8), with a mean of 7.9 (SD = 4.1) for the Executive, 12.0 (2.7) for the Emotional, and 15.1 (4.3) for the (Behavioral and Cognitive) Initiation subscales. All J-DAS subscale scores and the total score were significantly positively correlated (weak to strong) with the apathy measure (AS-14); the J-DAS Emotional component was not significantly correlated with the depression measure (BDI-II), while the J-DAS Executive and Initiation components were significantly positively correlated (moderate and weak, respectively) with the depression measure (Table S2). The Cronbach's standardized alpha for the J-DAS was 0.69. There were no floor or ceiling effects for any of the questionnaire measures. An exploratory factor analysis (EFA) with varimax (orthogonal) rotation was used to determine the substructure of the DAS scale, due to factors being uncorrelated (Table 1). Horn's parallel analysis indicated that three factors should be extracted. The mean measure of sample adequacy showed the sample to be factorable (0.88), further supported by a significant Bartlett's test for sphericity (P < 0.001). The three-factor solution cumulatively accounted for 38% of the total variance and the factors were subsequently labeled based on the themes of the items loading onto them. Overall, 87.5% of items saliently loaded onto the original DAS. Although the mapping to emotional apathy seems to lack consistency, over half of the items that mapped onto the Emotional Apathy subscale (D5 and D7) were those that were selected for the Brief-DAS, a short clinical version of the DAS.10 Moreover, analysis between DAS subscales and EFA-derived subscores showed strong positive correlations between corresponding DAS factor subscores (Table S2). As with the original DAS,6 the J-DAS had a three-factor structure mapping onto the executive, emotional, and initiation subtypes of apathy. It also has good internal consistency and reliability, in addition to good convergent validity against a one-dimensional apathy measure (AS-14) and good divergent validity against a gold-standard depression measure (BDI-II). Moreover, the AS-14 was significantly correlated with all J-DAS subscales, supporting the validity of the multidimensional apathy assessment while the inter-subscale correlations showed the nature of multidimensionality of the J-DAS the three subscales showed only weak correlation among them (r = 0.286 at most; Emotional–Initiation). The J-DAS is the first valid and reliable tool in Japanese for assessing multidimensional apathy. It can be used for assessing the general trait motivation of healthy individuals in daily life. Further research should aim to explore the apathy subtype profiles using the J-DAS in neurodegenerative, neurological, and psychiatric conditions, which would extend the understanding of apathy transculturally. Preparation of this manuscript was supported by Grants 18K07558 and 19K14481 from the Japan Society for the Promotion of Science KAKENHI. R.R. was funded by the Motor Neurone Disease Scotland and Motor Neurone Disease Association. Appendix S1 Supporting information including the details of method and the J-DAS scoring sheet in Japanese. Table S1 Item list, assessment, and scoring sheet of Japanese version of Dimensional Apathy Scale. Table S2 Correlations between Japanese version of Dimensional Apathy Scale (J-DAS) subscales and total, Beck's Depression Inventory II (BDI-II), Apathy Scale (AS-14), and exploratory factor analysis (EFA)-derived subscores. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

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