Predictive ability of the total score of the Kihon checklist for the incidence of functional disability in older Japanese adults: An 8-year prospective study.

Aim: To investigate the association between the total score of the Kihon checklist (t-KCL score) and functional disability over an 8-year follow-up period, and to examine whether the t-KCL score in the basic model with risk factors contributes to the incremental predictive ability for functional disability among older adults.

Methods: We followed 2209 older adults aged ≥65 years without functional disability at baseline. The t-KCL score was determined using a baseline survey questionnaire. Functional disability was defined based on information from long-term care certifications. The association between the t-KCL score and functional disability was examined using the Cox proportional hazards model. The incremental predictive ability of the t-KCL score for functional disability was evaluated by the difference of the C-statistic, category-free net reclassification improvement (NRI), and integrated discrimination improvement (IDI).

Results: The median follow-up period was 7.8 years, and 557 participants developed functional disability. The adjusted hazard ratio (95% confidence interval [CI]) of functional disability for a 1-point increase of the t-KCL score was 1.08 (1.06-1.10). Adding the t-KCL score to the basic model significantly improved the C-statistic (95% CI) from 0.747 (0.728-0.768) to 0.760 (0.741-0.781). When the t-KCL score was added to the basic model, the NRI and IDI were 0.187 (95% CI: 0.095-0.287) and 0.020 (95% CI: 0.012-0.027), respectively.

Conclusions: The t-KCL score had an independent positive association with functional disability over an 8-year follow-up. Furthermore, adding the t-KCL score to the basic model improved the predictive ability for functional disability. Geriatr Gerontol Int 2022; 22: 723-729.