The life-course changes in muscle mass using dual-energy X-ray absorptiometry: The China BCL study and the US NHANES study.

backgroundSarcopenia is an important indicator of ill health and is linked to increased mortality and a reduced quality of life. Age-associated muscle mass indices provide a critical tool to help understand the development of sarcopenia. This study aimed to develop sex- and age-specific percentiles for muscle mass indices in a Chinese population and to compare those indices with those from other ethnicities using the National Health and Nutrition Examination Survey (NHANES) data.

methodsWhole-body and regional muscle mass was measured by dual-energy X-ray absorptiometry (DXA) in participants of the China Body Composition Life-course (BCL) study (17 203 healthy Chinese aged 3-60 years, male 48.9%) and NHANES (12 663 healthy Americans aged 8-59 years, male 50.4%). Age- and sex-specific percentile curves were generated for whole-body muscle mass and appendicular skeletal muscle mass using the Generalized Additive Model for Location Scale and Shape statistical method.

resultsValues of upper and lower muscle mass across ages had three periods: an increase from age 3 to a peak at age 25 in males (with the 5th and 95th values of 41.5 and 66.4 kg, respectively) and age 23 in females (with the 5th and 95th values of 28.4 and 45.1 kg, respectively), a plateau through midlife (30s-50s) and then a decline after their early 50s. The age at which muscle mass began to decline was 52 years in men with the 5th and 95th percentile values of 43.5 and 64.6 kg, and 51 years in women with the 5th and 95th percentile values of 31.6 and 46.9 kg. Appendicular skeletal muscle mass decreased earlier than whole body muscle mass, especially leg skeletal muscle mass, which decreased slightly after age 49 years in both sexes. In comparison with their US counterparts in the NHANES, the Chinese participants had lower muscle mass indices (all P < 0.001) and reached a muscle mass peak earlier with a lower muscle mass, with the exception of similar values compared with adult Mexican and White participants. The muscle mass growth rate of Chinese children decreased faster than that of other races after the age of 13.

conclusionsWe present the sex- and age-specific percentiles for muscle mass and appendicular skeletal muscle mass by DXA in participants aged 3-60 from China and compare them with those of different ethnic groups in NHANES. The rich data characterize the trajectories of key muscle mass indices that may facilitate the clinical appraisal of muscle mass and improve the early diagnosis of sarcopenia in the Chinese population.