Abstract
Background
Impaired physical performance is common in older people with advanced chronic kidney disease. It is unclear which metabolic derangements contribute to this impairment. This analysis examined cross-sectional associations between renal biochemical indices and physical performance in older people with advanced chronic kidney disease.
Methods
We analysed data from the BiCARB multicentre trial, which enrolled patients aged 60 and over, with chronic kidney disease stage 4 or 5, not on dialysis, and with serum bicarbonate <22 mmol/L. Participants undertook baseline Short Physical Performance Battery (SPPB), grip strength and six minute walk test. Renal biochemistry (serum creatinine, cystatin C, phosphate, bicarbonate), haemoglobin, and NT-pro-B-type natriuretic peptide (NTproBNP) were measured at baseline. Associations were tested using Spearman’s rho and generalised linear modelling using forced entry was used for multivariable regression analysis.
Results
The analysis included 300 participants (mean age 74 years; 86 [29%] women). Mean baseline SPPB was 8.1 points (SD 2.3); mean six-minute walk distance was 311 m (SD 132). Age (r = −0.27, p < 0.001) and BNP (r = −0.27, p < 0.001) were most strongly associated with the SPPB. Age (r = −0.33, p < 0.001), haemoglobin (r = 0.24, p < 0.001), cystatin C (r = −0.21, p < 0.001) and NTproBNP (r = −0.32, p < 0.001) were most strongly associated with six-minute walk distance. For grip strength, age (r = −0.35, p < 0.001), cystatin C (r = −0.24, p < 0.001), and NTproBNP (r = −0.31, p < 0.001) were most strongly associated in men, with similar but weaker associations for women. Creatinine and bicarbonate concentrations were not significantly associated with any physical performance measures. Factors in multivariable regression independently associated with six-minute walk distance were age, sex, BMI, cystatin C, phosphate and NTproBNP; with SPPB were age and BMI; and with grip strength were age, sex and cystatin C.
Conclusions
Some biochemical markers related to kidney function are modestly associated with physical performance in older people with advanced chronic kidney disease; patterns differ between different performance measures.
Associations between frailty, physical performance, and renal biomarkers in older people with advanced chronic kidney disease
