Assessment of methods of evaluating sarcopenia in old dogs.

OBJECTIVE: To evaluate clinically applicable methods of assessing lean body mass in dogs and compare muscle mass and inflammatory markers in healthy young and old dogs. ANIMALS: 9 healthy young (1 to 5 years old) and 10 old (> 8 years old) Labrador Retrievers with a body condition score of 5 to 6 of 9. PROCEDURES: Radiography of the thoracolumbar region was performed for measurement of epaxial muscle height at the level of T13-L1. Computed tomographic images were obtained for the measurement of the epaxial and temporal muscles. Ultrasonography also was performed for regional muscle measurements at these same sites and the quadriceps muscle. Serum C-reactive protein, insulin-like growth factor-1, and tumor necrosis factor-α concentrations also were measured, and dogs' activity for 14 days was assessed with an activity monitor.
RESULTS: Mean epaxial muscle area measured by ultrasonography was significantly lower in the old group, compared with the young group, whereas epaxial muscle area measured by CT was only significantly lower in the old group after normalization for vertebral height. Neither temporal and quadriceps muscle measurements nor serum C-reactive protein or insulin-like growth factor-1 concentrations were significantly different between age groups. Tumor necrosis factor-α concentrations were undetectable in all dogs. CONCLUSIONS AND CLINICAL RELEVANCE: This study documented reduced epaxial muscle area in healthy old Labrador Retrievers, consistent with the syndrome of sarcopenia. Ultrasonography and CT were feasible methods of measuring epaxial muscle area, but much additional research is required to assess this method. A better understanding of underlying mechanisms of sarcopenia as well as methods for slowing progression is needed.