Translation, Adaptation, and Validation of the SF-36 Health Survey for Use in Japan

Abstract

Development of the Japanese SF-36 was completed in two phases: Phase 1: Japanese version 1.1 was produced according to International Quality of Life Assessment (IQOLA) project guidelines, but some results of psychometric tests were unexpected. First, scores varied little across physical-functioning items. Second, using factor analysis, we could not clearly distinguish the scales designed to measure the “physical” component of quality of life from those designed to measure the “mental” component. Phase 2: Focus-group discussions revealed that limited had often been interpreted as limited by a doctor. Therefore, is difficult to do was used instead (version 1.2). Results of two surveys indicated that version 1.2 yields scores that are reliable by internal consistency and test–retest standards and yields two principal components. In Japan, however, the pattern of correlations between some scales and the principal components differs from that in the United States. Iterative use of qualitative and quantitative methods was very important in developing the Japanese SF-36.

Introduction

Studies of health status and quality of life in Japan have become increasingly common [1]. Of the health-status measures used in Japan, some were developed domestically and others are translations of instruments originally developed in other countries. Among those translated into Japanese are both disease-specific measures, including Zung’s Self-Rating Depression Scale [2] and the Chronic Respiratory Disease Questionnaire [3], and generic instruments, including the Sickness Impact Profile [4] and the Nottingham Health Profile [5].

The SF-36 Health Survey is a questionnaire used to measure health status in general. In the SF-36, one item is designed to assess perceived change in health status, and each of the remaining 35 items contributes to a score on one of eight scales: physical functioning (PF), role-physical (RP), bodily pain (BP), general health perception (GH), vitality (VT), social functioning (SF), role-emotional (RE), and mental health (MH). Scores on these eight scales can be used to compute a summary index of physical health and a summary index of mental health. This structure is referred to as the SF-36 measurement model [6].

The International Quality of Life Assessment (IQOLA) network was established to translate and adapt the SF-36 for use in languages other than U.S.-English [7]. The founding members of the IQOLA Project represented 14 countries and 16 languages. With one exception, all 16 languages are closely related—Japanese is the only one that did not develop from Indo–European. In addition, Japan is the only one of those 14 counties in which Western culture is not dominant. Against this backdrop of linguistic and cultural differences, we translated the U. S.-English version of the SF-36 into Japanese and adapted it for use in Japan.

Here, we document the translation and cultural adaptation of the SF-36 for use in Japan, and the results of the initial psychometric testing of the Japanese version. We describe the process in chronological order, for two reasons. First, the development of the Japanese version involved two phases, each with its own methods and results (Figure 1); and second, we want to emphasize the importance of the fact that translation, evaluation (both qualitative and quantitative), and revision were done iteratively. Part I of this article describes phase 1, which included most of the translation and adaptation, and the first quantitative test. Some results of that test were unexpected, which made phase 2 necessary. Part II of this article describes phase 2, which included qualitative reevaluation, the resulting revisions, and further quantitative tests.