Quality of Life and Health-Related Quality of Life over 1 Year in Older Women: Monitoring Stability and Reliability of Measurement

Abstract

Assessing quality of life (QOL) and health-related quality of life (HRQOL) in older adults is important. Yet, limited research is available on the stability of these constructs and the psychometric properties of QOL [e.g., Satisfaction with Life Scale (SWLS)] and HRQOL [e.g., Short-Form 12 Health Survey (SF-12)] measures in this population. Such knowledge is important for designing and interpreting interventions. We examined stability of QOL (SWLS) and HRQOL (SF-12) and their test–retest reliability, measurement error, and interpretability over 1 year in older Black and White women (n = 230). Stability and reliability were ascertained through paired sample t tests and intraclass correlation coefficients (ICCs). Standard error of measurement and coefficient of variation assessed measurement error. Smallest detectable change estimated score interpretability. QOL and HRQOL remained stable; ICC values indicated moderate reliability for the SWLS and SF-12 (SWLS = 0.73, SF-12 Physical Composite Summary = 0.69, SF-12 Mental Composite Summary = 0.58). Measurement error and interpretability estimates were similar for both the SWLS and SF-12. Interpretability estimates indicated a change in score of around 33 % may represent an important change. We provide novel data for selecting and interpreting QOL and HRQOL measures contributing to a better understanding of intervention efficacy.