Impact of Longitudinal Changes in Dynamic Lower-Limb Function on Care-Needs Certification: A 4-Year Prospective Study of Older Women Attending Community Gathering Places (Kayoi-no-ba).

Background

Japan's rapidly aging society faces a critical challenge in sustaining the public long-term care insurance (LTCI) system. Community gathering places (Kayoi-no-ba) have been promoted for preventive care, but the predictive value of longitudinal changes in physical performance measures (PPMs) within these settings is not fully understood.

Objectives

Our objective was to clarify the association between baseline PPMs and their longitudinal change over four years with subsequent care-needs certification among community-dwelling older women.

Methods

We conducted a 4-year prospective study of independent older women (n = 223-226), assessing handgrip strength (HGS), Timed Up and Go (TUG), the 30-second chair stand test (CS-30), and the one-leg standing test (OLST). Analysis 1 examined baseline risk; Analysis 2 tracked functional transition (maintenance vs. decline) among those at "no risk" at baseline.

Results

Baseline PPM status was not significantly associated with future care-needs certification after adjusting for age and BMI. A longitudinal decline in TUG and CS-30 was associated with a significantly higher risk of certification (TUG: Hazard Ratio [HR] = 17.34, p < 0.001; CS-30: HR = 7.087, p = 0.002), which remained significant after Benjamini-Hochberg false discovery rate correction for multiple comparisons. However, a sensitivity analysis excluding participants certified before their 2023 re-measurement showed that the CS-30 association was no longer supported, while TUG remained nominally significant but with an extremely wide confidence interval (HR = 18.99, 95% CI 1.155-312.390, p = 0.039) reflecting very few events. A complementary continuous-change analysis corroborated this pattern (TUG: HR = 2.34 per 1-SD worsening, 95% CI 1.64-3.33, p < 0.001); no association was observed for HGS, CS-30, or OLST in this or the primary analyses.

Conclusions

A longitudinal decline in TUG performance may be associated with increased care-needs certification risk among older women, but this finding is sensitive to the temporal ordering of measurement and certification and requires confirmation in larger, prospective studies. The CS-30 finding did not withstand sensitivity analysis and should not be treated as a robust predictor.