Agreement between upper and lower limb measures to identify older adults with low skeletal muscle strength, muscle mass and muscle quality

Background Identifying low skeletal muscle strength (SMS), skeletal muscle mass (SMM) and skeletal muscle quality (SMQ) is pivotal for diagnosing sarcopenia cases. Age-related declines in SMS, SMM, and SMQ are dissimilar between the upper (UL) and lower limbs (LL). Despite this, both UL and LL measures have been used to assess SMS, SMM and SMQ in older adults. However, it is not clear whether there is agreement between UL and LL measures to identify older adults with low SMS, SMM and SMQ. Objective To investigate the agreement between UL and LL measures to identify older adults with low SMS, SMM and SMQ. Methods Participants (n = 385; 66.1 +/- 5.1 years; 75,4% females) performed the handgrip strength test (HGS) and the 30-s chair stand test (CST) to assess UL- and LL-SMS, respectively. The SMM was assessed by dual-energy X-ray absorptiometry (DXA). The UL-SMQ was determined as: handgrip strength (kgf) divided by arm SMM (kg). LL-SMQ was determined as: 30-s CST performance (repetitions) divided by leg SMM (kg). Results below the 25th percentile stratified by sex and age group (60-69 and 70-80 years) were used to determine low SMS, SMM and SMQ. Cohen's kappa coefficient (kappa) was used for the agreement analyses. Results There was a slight and non-significant agreement between UL and LL measures to identify older adults with low SMS (kappa = 0.046; 95% CI 0.093-0.185; p = 0.352). There was a moderate agreement to identify low SMM (kappa = 0.473; 95% CI 0.371-0.574; p = 0.001) and a fair agreement to identify low SMQ (kappa = 0.206; 95% CI 0.082 to 0.330; p = 0.005). Conclusion The agreement between UL and LL measures to identify older adults with low SMS, SMM and SMQ is limited, which might generate different clinical interpretations for diagnosing sarcopenia cases.