Background: The Older people Quality of Life-7 domains (OQoL-7) is a 28-item multidimensional questionnaire developed to measure community-dwelling older people's QoL. The OQoL-7 assesses both importance of and satisfaction in seven QoL domains (Material resources; Close entourage; Social and cultural life; Esteem and recognition; Health and mobility; Feeling of safety; and Autonomy). This study aimed to investigate concurrent and construct validity of the OQoL-7. A secondary aim was to compare different methods of weighting participants' ratings of satisfaction according to their individual ratings of importance, as compared to the OQoL-7 total score (unweighted).
Methods: Data came from the first and second samples of the Lausanne cohort 65+ study, assessed at the same age of 72-77 years in 2011 (N = 1117) and 2016 (N = 1091), respectively. To assess concurrent validity, the OQoL-7 was compared to other measures of the same concept (single QoL item) or related concepts (self-rated health, SF-12). Construct validity was tested by comparing subscores in the seven QoL domains in the presence and absence of two stressful events during the preceding year (financial difficulties and relationship difficulties). The effect of importance weighting was assessed using moderated regression analysis.
Results: The OQoL-7 total score was significantly associated with the single QoL item (Spearman's rho 0.46), self-rated health (Spearman's rho 0.34), SF-12 physical (Spearman's rho 0.22) and mental (Spearman's rho 0.28) component scores. Large differences (Cohen's d > 0.8) were observed in the presence or absence of stressful events in the expected QoL domains: "Material resources" in the presence or absence of "Financial difficulties" (Cohen's d 1.34), and "Close entourage" in the presence or absence of "Relationship difficulties" (Cohen's d 0.84). Importance weighting resulted in a very small improvement in the prediction of the single QoL item (ΔR2 0.018). All results were highly consistent across 2011 and 2016 samples.
Conclusions: The OQoL-7 showed adequate concurrent and construct validity in two samples of older people. In future studies, the decision to use weighted or unweighted scores will depend on the priority given to either optimizing the prediction of QoL or limiting the burden on respondents and the amount of missing data.
Keywords: Importance weighting; Older people; Quality of life; Scale; Validity.