2025 Volume 74 Issue 5 Pages 498-508
The Washington Group Short Set on Functioning (WGSS), an internationally comparable measure for identifying persons with disabilities (PWDs), was introduced for the first time in a national survey in Japan. Understanding the psychometric properties of this measure is crucial to appropriately use disability statistics based on the WGSS for improving disability-related policy making and welfare services in Japan. The purpose of this study is two-folds: (1) to describe the difference of disability prevalences between the new measure and existing domestic definitions of disability, namely, possession of certificates for disability and designated intractable diseases, and (2) to explore influence of aging on the difference. This cross-sectional descriptive study used secondary data from a representative survey on PWDs, Seikatsu no Shizurasa Chosa, in 2022, which translates into the Comprehensive Survey of Persons with Difficulties. The analysis included data from individuals aged ≥ 5 years (n=11,346, mean age; 64.0±23.4). The eligible data were divided into ten groups based on the type of certificate and disability; physical disability certificate for vision impairment (a), hearing impairment (b), limb or trunk impairment (c), visceral impairment (d), unknown (e), mental disorder certificate (f), intellectual disability certificate (g), intractable disease (h), multiple disabilities (i), and no certificates (j). Disability was defined on the WGSS following the recommended criteria; at least one “a lot of difficulty” or #8220;cannot to do at all” in six WGSS-related questions. The percentage of disability defined by the WG-SS were calculated for each group and its subgroups stratified by age group (younger group (Y); < 65 years, older group (O); ≥ 65 years). Comparisons between types of disability and age groups were conducted using Chi-square test. Overall, the percentage of disability as defined by the WGSS was 52.6% (Y; 40.7%, O; 60.5%) among all eligible data. In alphabetical order of the groups, the percentages were 92.5%，67.8%，55.0%，33.6%，52.7%，35.0%，46.2%，39.7%，68.2%，53.0%. Significant differences between the groups were observed (p<0.05). In all groups except for (a), (b), and (g), the older age groups showed significantly higher percentages than the younger age groups(p<0.05). The WGSS showed distinctive characteristics; lower prevalence of disability, in particular younger age group, compared with the existing disability definitions. This difference should be considered if the WGSS is used for policymaking and service planning for PWDs.
