A Psychometric Evaluation of the Measurement of Agency in Adults with Physical Disabilities in Long-Term Care

Abstract

Background: Evaluations of healthy aging tend to focus on a person’s lived environments, their intrinsic capacities (physical and mental capacities to act), and the interplay between the two, as these factors shape the aging process. Currently, there is a lack of research that has identified positive indicators of intrinsic psychological capacities, particularly for adults living with disabilities in long-term care (LTC) homes. Personal agency (beliefs about one’s own abilities to act to achieve goals) and interpersonal agency (beliefs about one’s ability to engage with others to achieve goals) might be useful strengths-based indicators of intrinsic psychological capacities because they reflect individuals’ beliefs about the strategies that they use to achieve control over life. The Personal Agency Scale (PAS) and Interpersonal Agency Scale (IPAS) are measures of these constructs, but little is known about their psychometric properties. Objectives: The primary aim of the study was to test the psychometric characteristics of the PAS and IPAS within the context of adults who are aging with physical disabilities in a LTC home. The specific objectives were to estimate item response variation and internal reliability of these scales, test concurrent validity, and assess their sensitivity to change over time. Methods: Repeated-measures data taken 6-months apart from a sample of 59 adults aging with physical disabilities in a long-term care home were analysed. Between waves of data collection, participants experienced changes to their physical and social environments that were likely to have changed subjects’ levels of agency. Item-analyses were conducted to estimate internal consistency of the scales, including Cronbach’s alpha and assessment of response distributions for all items. Generalized Estimating Equations was used to test for known education-group comparisons in agency scores and known correlations between agency scores and depression to assess the construct validity of the PAS and IPAS. Paired Test-Statistics were used to test for changes in individuals’ levels of agency from baseline to 6-month follow-up. Results: This study found mixed evidence regarding the psychometric properties of the PAS and IPAS. PAS measurements were found to have sufficient internal consistency at both timepoints whereas the IPAS measurements were only internally consistent at baseline. Item response variation was low, particularly for the IPAS at the 6-month follow-up. No education group differences in PAS scores or IPAS scores were found. Furthermore, there was no evidence of an association between depression and agency scores. Individuals’ PAS and IPAS measurements were of similar magnitude at both timepoints. Interpretation: This study did not provide sufficient evidence to endorse the use of the PAS and IPAS as an indicator of intrinsic psychological capacity for older adults living with physical disabilities in LTC, in their current form. Future psychometric evaluations of these measures should consider the impact adopting a 5-point verbal response scale and adding a time-reference to item stems on measurement performance.