42 Is Mitochondrial Function Measured by 31P Magnetic Resonance Spectroscopy Associated with Physical Performance in Older People with Functional Impairment?

Background Mitochondrial dysfunction has been proposed as a therapeutic target to improve muscle strength and endurance, but the contribution that mitochondrial dysfunction makes to impaired skeletal muscle performance in older people remains unclear. We studied the relationship between phosphocreatine recovery rate (a measure of skeletal muscle mitochondrial function) and physical performance in older people. Methods We analysed data from the Allopurinol in Functional Impairment (ALFIE) trial. Participants aged 65 and over, who were unable to walk 400 m in six minutes, underwent 31P magnetic resonance spectroscopy of the calf after exercise at baseline and at 20 weeks follow up. The phosphocreatine recovery half-life time (t-half) was derived as a measure of mitochondrial function. Participants also undertook the 6-minute walk distance, the Short Physical Performance Battery test (SPPB), and had muscle mass measured using bio-impedance analysis. Bivariate correlations and multivariable regression analyses were conducted to determine associations between t-half and baseline factors. Results One hundred and seventeen people underwent baseline 31P magnetic resonance spectroscopy, mean age 80.4 years (SD 6.0); 56 (48%) were female. Mean 6-minute walk was 291 m (SD 80) and mean SPPB score was 8.4 (SD 1.9). T-half was significantly correlated with SPPB score (r = 0.22, p = 0.02) but not with 6-minute walk distance (r = 0.10, p = 0.29). In multivariable linear regression, muscle mass and weight, but not t-half, were independently associated with SPPB score and with 6-minute walk distance. The change in t-half between baseline and 20 weeks was not significantly associated with the change in SPPB (r = 0.03, p = 0.79) or with the change in 6-minute walk distance (r = −0.11, p = 0.28). Conclusion Muscle mass, but not phosphocreatine recovery time, was associated with Short Physical Performance Battery score and 6-minute walk distance in this cohort of older people with functional impairment.