Population norms and meaningful differences for the Assessment of Quality of Life (AQoL) measure

Objective: The Assessment of Quality of Life (AQoL) instrument is widely used in Australian health research. To assist researchers interpret and report their work, this paper reports population and health status norms, general minimal important differences (MIDs) and effect sizes. Method: Data from the 1998 South Australian Health Omnibus Survey (n = 3,010 population-based respondents) were analysed by gender, age group and health status. Data from four other longitudinal studies were analysed to obtain estimated MIDs. Results: The mean (SD) AQoL utility score was 0.83 (0.20). Gender and age subgroup differences were apparent; the mean scores for women were consistent until their 50s, when scores declined. Greater variability was observed for males whose scores declined more slowly but consistently between 40-80 years. For both genders, those aged 80+ years had the lowest scores. When assessed by health status, those reporting excellent health obtained the highest utility scores; progressive declines were observed with decreasing health status. Effect sizes of 0.13 or greater may reflect important differences between groups. A difference in AQoL scores of 0.06 utility points over time suggests a general MID. Conclusions: AQoL population norms, MIDs and effect sizes can be used as reference points for the interpretation of AQoL data. These findings add to the growing evidence that the AQoL is a robust and sensitive measure that has wide applicability. Implications: The availability of population norms will assist researchers using the AQoL to more easily interpret and report their work.