Reliability, validity, and responsiveness of the Japanese version of International Restless Legs Syndrome Study Group rating scale for restless legs syndrome in a clinical trial setting

Test-retest reliability of the Japanese version of the International Restless Legs Syndrome Study Group Rating Scale (J-IRLS) is 0.877.

• J-IRLS demonstrated good test-retest reliability with an intra-class correlation coefficient of 0.877.
• Correlation coefficients between J-IRLS total score and Clinical Global Impression Scale scores were 0.804 and 0.796, indicating strong concurrent validity.
• Factor analysis identified a two-factor structure within the J-IRLS items.
• Exploratory analysis suggested a third factor related to the Japanese version of the Pittsburgh Sleep Quality Index.
• Significant correlations were observed between changes in J-IRLS total score and both Clinical Global Impression Improvement and Patient Global Impression after treatment.

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