1 Department of Medicine School of Physical and Occupational Therapy, McGill University, Montreal, Canada. nancy.mayo@mcgill.ca.
2 Divisions of Clinical Epidemiology, Geriatrics, Experimental Medicine, McGill University Health Center (MUHC), Montreal, Canada. nancy.mayo@mcgill.ca.
3 Center for Outcomes Research and Evaluation (CORE), MUHC-Research Institute, 5252 de Maisonneuve, Montreal, QC, H4A 3S5, Canada. nancy.mayo@mcgill.ca.
4 School of Rehabilitation Therapy, Queen's University, Kingston, ON, Canada.
5 Department of Physical Therapy, College of Rehabilitation Sciences, Rady Faculty of Health Sciences, University of Manitoba, R106-771 McDermot Ave, Winnipeg, MB, R3E 0T6, Canada.
6 Rehabilitation Hospital, RR323A, 800 Sherbrook St, Winnipeg, Canada.
7 Center for Health and Aging, Pasadena, CA, 91106, USA.
8 Department of Public Health & Sports Sciences, Faculty of Health and Life Sciences, University of Exeter Medical School, University of Exeter, Medical School Building, College of Medicine and Health, St Lukes Campus, Heavitree Road, Exeter, EX12LU, UK.
9 Department of Public Health, Erasmus MC University Medical Center Rotterdam, PO Box 2040, 3000 CA, Rotterdam, The Netherlands.
10 Concordia University, Montreal, QC, Canada.
11 Department of Philosophy, McGill University, Leacock Building, Room 933, Montreal, Canada.
12 School of Nursing, UT Health San Antonio, San Antonio, USA.
13 Center for Outcomes Research and Evaluation (CORE), Research Institute of McGill University Health Center, Montreal, Canada.
14 Faculty of Medicine, McGill University, Montreal, Canada.
15 School of Rehabilitation Science, McMaster University, 1400 Main Street West, Hamilton, ON, L8S 1C7, Canada.

Introduction: Through interviews with 148 older persons from four countries and in four languages, the content for a 17-item measure of active living was developed. The purpose of this paper is to present further evidence of the extent to which this new measure, Older Persons Active Living (OPAL), is "fit-for-purpose" for measuring the extent of active living at one point in time.

Methods: A cross-sectional study was carried out on a population aged 65 + and living independently, drawn from a participant panel, HostedinCanada, sampling people from Canada, United States, United Kingdom, and Netherlands. The survey instrument comprised the OPAL questionnaire rated on importance and frequency, sociodemographics, and information on physical and mental function. The argument-based approach to validity framed the analyses. Logistic regression, structural equation modeling, ordinary least-squares regression, and correlation were used to generate estimates for parameters underpinning validity evidence.

Results: A total of 1612 people completed the survey, 100 to 400 people across the 6 country-language strata. The proportion of people rating the items as extremely or quite important ranged from 60 to 90%, with no important differences between men and women and few differences between strata. A single-factor structure was supported. The ordinality of the response options justified an additive total score yielding a near normal distribution (mean: 33.1; SD: 11.5; range 0-51). Correlations with other measures of converging constructs were of moderate strength (~ 0.50), and differences across groups known to affect functioning and health were observed, suggesting a Miminal Important Difference (MID) of 6 out of 51.

Conclusion: The results of this study provide evidence that the 17-item OPAL measure is fit for the purpose of estimating the extent to which older persons are living actively at one point in time.