Abnormal maximal tubular reabsorption of phosphate as a novel biomarker of physical dysfunction in older adults.

BACKGROUND

Physical dysfunction is a preclinical stage of disability in older adults, linked to severe adverse outcomes such as death and hospitalization. Maximal tubular reabsorption of phosphate (TmP/GFR), as a key biomarker of phosphate metabolism, may be related to physical dysfunction, but this relationship has not yet been explored.

METHODS

Using data from the Rugao Longitudinal Ageing Study (RLAS), longitudinal logistic regression was employed to explore the relationship between abnormal TmP/GFR and physical dysfunction. For validation, the UK Biobank dataset was combined, and mendelian randomization (MR) was conducted to investigate causality. The maximal phosphate reabsorption was assessed using TmP/GFR, while physical dysfunction were evaluated through grip strength and the Timed Up and Go (TUG) test.

RESULTS

During the four-year follow-up, 89 (13.55%) and 279 (40.85%) participants were identified as having a new onset of decreased grip and TUG. The abnormal TmP/GFR population had a significantly higher risk of decreased grip (OR 2.03, 95% CI 1.20-3.49) and decreased TUG (OR 1.49, 95% CI 1.05-2.12). MR analysis demonstrated the causal effect of TmP/GFR dysfunction population had significantly lower grip and lower walking speed.

CONCLUSION

This study first identifies abnormal TmP/GFR as a novel biomarker of physical dysfunction in older adults. Additionally, its causal relationship further substantiates the reliability of this finding. Abnormal TmP/GFR enables early detection of physical dysfunction, facilitating the prevention of severe adverse outcomes.