Background and aims: Older adults' ever-improving health and changing lifestyles necessitate the development of a scale that can better measure their competence at a higher level. We developed the Japan Science and Technology Agency Index of Competence (JST-IC) via item analysis and assessed its psychometric properties.
Methods: Participants were 1306 community-dwelling older adults (623 men and 683 women, 74.0 ± 2.8 years old) who completed the 54-item draft JST-IC to determine their level of independence. Three procedures (including item selection, factor analyses, and reliability and validity analyses) were conducted to finalize the JST-IC and evaluate its psychometric properties.
Results: The item selection resulted in exclusion of 26 items for the following reasons: (a) 15 because of very high ratios (80% or more) of responders who answered "yes", (b) one because of gender differences (phi coefficient = 0.34), (c) five because of their weak association with the Tokyo Metropolitan Institute of Gerontology Index of Competence (TMIG-IC) (Pearson correlation coefficient of 0.30 or smaller), and (d) five because of redundancy of meaning with other items. Through factor analyses, we selected 16 items with a four-factor solution for the final version. JST-IC score exhibited a near-normal distribution and significant gender and age differences, and had moderate correlations with size of social network and level of subjective well-being and strong correlations with TMIG-IC score, physical fitness, and health literacy.
Conclusions: The JST-IC is useful for assessing competence at a higher level in community-dwelling older adults.
Keywords: Community-dwelling older adults; Competence; Functional capacity; Instrumental activities of daily living (IADL).