Comparative Analysis of the Japanese Version of the Revised Impact of Event Scale: a Study of Firefighters

Introduction: The Impact of Event Scale Revised (IES-R) has been used in various epidemiological studies to assess the prevalence of post-traumatic stress disorder (PTSD). Previous studies using the IES-R Japanese version to assess the mental health of firefighters were based on the premise that firefighters had experienced a traumatic event(s) as a matter of course. However, use of the IES-R-J does not indicate whether or not a traumatic event was experienced. The purpose of this study is to clarify the differences between: (1) IES-R-J high and low score groups; and (2) those who report symptoms similar to those of PTSD with and without having been being exposed to a traumatic event.

Methods: Questionnaire packets distributed to all 157 workers in a Japanese fire station included the IES-R, the Japan Brief Job Stress Questionnaire, a questionnaire regarding traumatic event experiences, and demographic questions. Participants who scored > or = 25 points on the IES-R-J scale were defined as the PTSD high risk (HR) group; those with scores < 25 points as the PTSD low risk (LR) group.

Results: One hundred thirty-one of the 157 subjects (83.4%) responded to the questionnaire; three were excluded from the analysis because of missing data. The mean total IES-R-J score was 14.9 +/- 15.2. Twenty-eight subjects scored in the PTSD HR group (> or = 25); 100 scored in the LR group (< 25). A total of 54 (42.2%) participants had experienced a traumatic event; 57.8% had not. In the HR group, 14 subjects had experienced a traumatic event and 14 had not. Participants who had experienced a traumatic event reported a higher incidence of intrusion/re-experience symptoms than did those who had not experienced a traumatic event. The level of social support significantly affected the risk for PTSD. Firefighters who scored > or = 25 on the IES-R-J and, thus, considered to be at high risk for the development of PTSD, were less confident about their health, experienced more job stressors and had less social support than did those whose IES-R-J scores were < 25. Having experienced a traumatic event was reported by only 42% of all the participants and by only 50% of those in the high risk PTSD group.

Conclusions: Although the IES-R is an easily-administered tool useful in epidemiological studies evaluating psychological stress, it is recommended that the questionnaire be amended to include a question regarding the existence of a threatened experience or event and to analyze the data using positive and negative predictive value methodology.