Evaluation of the association between impaired renal function and physical function among community-dwelling Japanese frail elderly based on the estimated glomerular filtration rate (eGFR)

Aim: Falls are major risk factors in nursing care and reported to be associated with low vitamin D levels or impaired renal function. It is unknown whether physical function is associated with impaired renal function. The aim of this study was to examine the association between estimated glomerular filtration rate (eGFR) (ml/min/1.73 m ²), vitamin D, and physical function in Japanese frail elderly. Methods: A cross-sectional survey was conducted in two towns (latitude 36 degrees north) from June 2006 to January 2008. Subjects counted of 109 community-dwelling frail elderly, aged 65 years and over (mean ± SD: 75.8 ± 5.2 yr) who attended a program for nursing care prevention. An interview was conducted based on a questionnaire. The serum levels of intact parathyroid hormone (iPTH), 25-hydroxyvitamin D (25 (OH) D), 1,25-dihydroxyvitamin D (125 (OH) ₂D), and creatinine were measured. eGFR (ml/min/1.73 m ²) was calculated using the Modification of Diet in Renal Disease formula. The following functional fitness tests were performed: timed up and go (TUG), a 5-meter walk, functional reach (FR), one leg stance, tandem stance, and grip strength. Results: Of the subjects, 59.6% experienced falls, 75.2% experienced stumbling at least once during the past year. eGFR was 68.0± 14.1 ml/min/1.73 m ² in the subjects. The prevalence of eGFR<60.0 ml/min/1.73 m ² was 30%. The subjects with eGFR ≥60 ml/min/1.73 m ² showed significantly better results for FR, one leg stance, and tandem stance than those with eGFR< 60 ml/min/1.73 m ². Multiple liner regression analysis suggested that FR and tandem stance were significantly affected by eGFR. Conclusions: Our data suggest that assessment of renal function seems to be significant when we consider balance ability in the frail elderly.