Normative Data for Lean Mass Using FNIH Criteria in an Australian Setting

Recommendations from the FNIH Sarcopenia Project are that appendicular lean mass (ALM, kg) adjusted for body mass index (BMI, kg/m²) be used for identifying low lean mass, with ALM/BMI cutpoints of < 0.789 m² for men and < 0.512 m² for women. We report normative ALM/BMI values for Australian adults, and compare the performance of cutpoints derived from reference values for this population with FNIH values for identifying low lean mass. Body composition was measured by DXA (Lunar) for 1411 men and 960 women, aged 20-93 years, from the Geelong Osteoporosis Study, a population-based study in Australia. Sex-stratified means and standard deviations for DXA-derived ALM/BMI were generated for each age-decade, and cutpoints equivalent to T-scores of - 2.0 were derived using reference data for 374 men and 308 women aged 20-39 years. Mean ALM/BMI values were greater for men than women, and decreased with age in both sexes. Cutpoints for ALM/BMI corresponding to T-scores of - 2.0 were 0.827 m² for men and 0.518 m² for women. For individuals aged 65+ years, cross-classification of low lean mass according to FNIH criteria (ALM/BMI < 0.789 m² men and < 0.512 m² women) in comparison with our cutpoints for ALM/BMI showed overall agreement of 94.6% for men and 99.0% for women (κ 0.73 and 0.89, respectively). We report good agreement for low ALM indexed to BMI, particularly for women, between classifications based on recommendations from the FNIH Sarcopenia Project for identifying clinically significant weakness, with low values identified within our population distribution of ALM/BMI.