An off-target scale limits the utility of Short Warwick-Edinburgh Mental Well-Being Scale (SWEMWBS) as a measure of well-being in public health surveys

Objectives: To assess the utility and measurement properties for the well-being scale Short Warwick-Edinburgh Mental Well-Being Scale (SWEMWBS) in a Swedish general population survey. Study design: A cross-sectional survey study. Methods: Data were retrieved from the 2018 public health survey in Stockholm County, containing a random sample of 22 856 persons stratified to be representative for the municipalities and districts within the region. The data were analyzed according to Rasch Measurement Theory. Results: Person attribute values are positively skewed (mean 2.32, SD 1.85), with wide gaps in the item threshold attribute values. Overall item fit statistics were acceptable, and person measurement separation reliability was 0.83, indicating three statistically distinct ranges in the estimated well-being values. Conclusion: While the SWEMWBS items indicated acceptable fit to the Rasch measurement model, targeting of items to sample is skewed toward lower levels of well-being, and there is a ceiling effect. Thus, we suggest a careful reconsideration of SWEMWBS as a tool for use in general public health surveys, especially for assessing change over time and group differences, as there are large measurement uncertainties for the majority of cases when the population as a whole is sampled. We encourage revisions applying a coherent and comprehensive ordinal construct theory for well-being to fill the gaps in the upper end of the SWEMWBS scales' item thresholds. The addition of more challenging items would improve targeting for population-based surveys, increase reliability, and provide more actionable information that could be useful in improving individuals' well-being. (c) 2021 The Authors. Published by Elsevier Ltd on behalf of The Royal Society for Public Health. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).