Association Between the Functional Independence and Difficulty Scale and Physical Functions in Community-Dwelling Japanese Older Adults Using Long-term Care Services

The Functional Independence and Difficulty Scale (FIDS), a newly developed basic activities of daily living (BADL) assessment tool, assesses both independence and subjective difficulty of BADL performance. This patient-reported outcome measure has been shown to have acceptable internal consistency, concurrent validity, and reliability. However, little is known about the relationship between FIDS and objective measures of physical function among older Japanese adults using long-term care insurance services. This study aimed to reveal the relationship between FIDS and physical functions and to examine the concurrent validity of FIDS against physical functions. Participants of this cross-sectional, correlational research study included community-dwelling Japanese adults aged 65 years or older and certified as long-term care insurance service users with musculoskeletal disease, internal disease, cerebrovascular diseases without observable motor paralysis, and others. Data on physical functions, including muscle strength (grip strength and isometric knee extension muscle strength [IKEMS]), flexibility (range of motion [ROM] of hip flexion and knee flexion), balance (Modified Functional Reach Test [M-FRT]) and gait performance (timed 2.4-m walk), and BADL performance assessed by FIDS, were obtained. Associations between FIDS scores and physical functions were determined by Spearman correlation coefficient and partial correlations after controlling for subject age and sex. Data were collected on 53 participants (mean age = 81.9 years; 62.3% women). Spearman partial correlation coefficients controlled for sex and age between FIDS score and grip strength, IKEMS, ROM of hip flexion, ROM of knee flexion, M-FRT, and timed 2.4-m walk were 0.47 (P = .001), 0.44 (P = .001), 0.29 (P = .04), -0.05 (P = .73), 0.51 (P < .001), and -0.64 (P < .001), respectively. The strength of association was moderate for the M-FRT and 2.4-m walk and was low for grip strength and IKEMS. However, ROM of the knee showed no significant association and hip flexion had negligible association with FIDS. The FIDS, a patient-reported BADL assessment tool, mainly reflected balance and gait performance and had concurrent validity as an objective measure of balance and gait performance.