Factor structure of the General Health Questionnaire (GHQ-12) in subjects who had suffered from the 2004 Niigata-Chuetsu Earthquake in Japan: a community-based study

Abstract

Background: Factor structure of the 12-item General Health Questionnaire (GHQ-12) was studied by a survey of subjects who had experienced the 2004 Niigata-Chuetsu earthquake (6.8 on the Richter scale) in Japan.

Methods: Psychological distress was measured at two years after the earthquake by using GHQ-12 in 2,107 subjects (99.0% response rate) who suffered the earthquake. GHQ-12 was scored by binary, chronic and Likert scoring method. Confirmatory factor analysis was used to reveal the factor structure of GHQ-12. Categorical regression analysis was performed to evaluate the relationships between various background factors and GHQ-12 scores.

Results: Confirmatory factor analysis revealed that the model consisting of the two factors and using chronic method gave the best goodness-of-fit among the various models for factor structure. Recovery in the scale for the factor 'social dysfunction' was remarkably impaired compared with that of the factor 'dysphoria'. Categorical regression analysis revealed that various factors, including advanced age, were associated with psychological distress. Advanced age affected the impaired recovery of factor 'social dysfunction' score as well as total GHQ score.

Conclusion: The two-factor structure of GHQ-12 was conserved between the survey at five month and that at two years after the earthquake. Impaired recovery in the ability to cope with daily problems in the subjects who had experienced the earthquake was remarkable even at two years after the earthquake.

Figure 1

Relative frequency polygons for GHQ-12 score. GHQ-12 was scored by three different methods. In each method of scoring, the proportions of subjects with each score were plotted. Vertical dotted lines indicated the cutoff points for each scoring method.

Figure 2

Differences of lower scale points by age group of subjects. The relationship between age of subjects and GHQ scores is shown as mean and standard deviation values. The data obtained two years after the earthquake (second survey) are shown with the data obtained five months after the earthquake (first survey). Trends of GHQ scores with increasing age of subjects were analyzed by ANOVA (ANOVA) with Scheffe post hoc tests and Jonckheere-Terpstra Test (JT). The p value of each test is shown in the plot. The factor I score of age group years 40–49 was significantly lower than groups years 65–79 and 80-(*) in the first survey. Age group years 80-showed significantly higher factor I score than other age groups (†).