Factor structure and longitudinal measurement invariance of the K6 among a national representative elder sample of China

BACKGROUND: As the number of older people is rapidly growing, prevention, screening, and treatment of mental health problems (including anxiety and depression) in this population increasingly become a heavy burden to individuals, families, and even the whole society. The Kessler-6 screening measure (K6) is an efficient and effective instrument for general mental health problems. However, few studies have examined its measurement invariance across time, which is particularly important in longitudinal studies, such as exploring developmental trajectories of non-specific psychological distress and evaluating the effects of certain interventions. METHODS: The current study investigated the factor structure and the longitudinal measurement invariance of the K6 among a national representative elder sample of China. Longitudinal data in two survey waves (the year 2010, and the year 2014) from the China Family Panel Studies were drawn for secondary data analysis. A total of 3845 participants aged 60 years old and above (52.2% male, mean age = 66.99 years, SD = 5.93 years) responded to both waves of the survey. RESULTS: A comparison of four existing models with confirmatory factor analysis supported a two-factor solution of the K6. A series of multi-group confirmatory factor analyses further indicated that the K6 held strict longitudinal measurement invariance across time. Additionally, the internal consistency indices across time and the stability coefficients over time were acceptable. CONCLUSIONS: The findings further confirmed the psychometric defensibility of the K6 when used in the old Chinese population. The longitudinal measurement invariance justified comparisons of psychological distress scores among different measurement time points.