Association of change in muscle mass assessed by D₃-creatine dilution with changes in grip strength and walking speed

Background: Muscle mass declines with age. However, common assessments used to quantify muscle mass are indirect. The D₃-creatine (D₃Cr) dilution method is a direct assessment of muscle mass; however, longitudinal changes have not been examined in relation to changes in other measures of muscle mass, strength, and performance. Methods: A convenience sample of 40 men from the Osteoporotic Fractures in Men Study (mean age = 83.3 years, standard deviation = 3.9) underwent repeat assessment of D₃Cr muscle mass, dual-energy X-ray absorptiometry (DXA) lean mass, grip strength, and walking speed at two time points approximately 1.6 years apart (2014–2016). One-sample t-tests and Pearson correlations were used to examine changes in DXA total body lean mass, DXA appendicular lean mass/height², DXA appendicular lean mass/weight, D₃Cr muscle mass, D₃Cr muscle mass/weight, grip strength, walking speed, and weight. Results: D₃-creatine muscle mass, D₃Cr muscle mass/weight, grip strength, and walking speed all significantly declined (all P < 0.01). The change in DXA measures of lean mass was moderately correlated with changes in D₃Cr muscle mass. There was no significant correlation between the change in DXA measures of lean mass and change in walking speed (all P > 0.05). The change in D₃Cr muscle mass/weight was moderately correlated with change in walking speed (r = 0.33, P <.05). The change in grip strength was weakly correlated with the change in DXA measures of lean mass and D₃Cr muscle mass (r = 0.19–0.32). Conclusions: The results of our study provide new insights regarding the decline in muscle strength and D₃Cr muscle mass. The D₃Cr method may be a feasible tool to measure declines in muscle mass over time.