Validation of the Japanese translation of the Dysphagia Handicap Index

Background: We developed, and examined the reliability and validity of, a Japanese version of the Dysphagia Handicap Index (DHI; DHI-J), which is a self-reported measure to assess the quality of life (QOL) of individuals with dysphagia. Participants and methods: The DHI-J was developed via the back-translation method: the DHI was translated into Japanese and then translated back into English by a native English speaker. The back translation was discussed with and approved by the DHI's lead author. A total of 229 patients (119 males, 110 females; median age: 66 years) who underwent videofluorography at our hospital between January and December 2013 and 65 controls (23 males, 42 females; median age: 44 years) were included in the study. All the subjects completed the DHI-J and self-reported their dysphagia severity. Twenty-three patients repeated the procedure 1 week later. Patients' swallowing function was classified as "normal", "moderately impaired", or "severely impaired", and the DHI-J total scores were compared between the severity groups. Results: The internal consistency of the DHI-J was high (Cronbach's alpha=0.95), as was the test-retest reliability of the 23 patients who answered the questionnaire twice (intraclass correlation coefficient = 0.98, P<0.01). The DHI-J total score and its three subscale scores were significantly higher among the patients than among controls. A significant correlation (rho = 0.85) was observed between the DHI-J total score and self-reported dysphagia severity score. Regarding the comparison of DHI-J scores by severity groups, the DHI-J total scores significantly differed between the normal and moderately impaired groups, and the normal and severely impaired groups. However, the moderately and severely impaired groups showed no significant difference in scores. Conclusion: The DHI-J is a reliable and valid questionnaire for assessing the QOL of patients with dysphagia. However, we did not survey patients with cerebrovascular diseases; thus, the questionnaire must be validated for that patient group.