Individuals with Down syndrome possess lower handgrip strength, appendicular lean mass, and muscle quality versus weight-matched adults

Individuals with Down syndrome (DS) face accelerated musculoskeletal aging and increased sarcopenia, leading to functional limitations and health risks. Despite its potential value, research has yet to compare the muscle quality index (MQI) between adults with and without DS (NDS). We hypothesized that individuals with DS will have lower MQI values compared to NDS. Therefore, this study compared MQI between weight-matched peers with and without DS. Individuals with DS (n = 12) were weight-matched against a group of NDS (n = 12). Appendicular lean mass (ALM) was measured using dual-energy X-ray absorptiometry. Handgrip strength (HGS) was measured using a handheld dynamometer. MQI was computed as follows: 1). MQI_ARMS: (lean mass of upper limbs; HGS of right + left hand); and 2). MQI_{ARMS + LEGS}: (lean mass of upper and lower limbs; HGS of right + left hand). The DS group showed lower mean values for arm lean mass (LM_ARMS) (3.95 ± 1.49 kg vs. 5.17 ± 2.14 kg, d = 0.97) and ALM (15.50 ± 4.01 kg vs. 23.04 ± 6.30 kg, d = 1.55) against NDS. NDS also demonstrated higher HGS (all P < 0.01) than DS for HGS_RIGHT (d = 1.81), HGS_LEFT (d = 1.55), and HGS_SUM (d = 1.81). Additionally, the NDS group exhibited large differences in MQI_ARMS versus DS (11.98 ± 2.00 and 8.90 ± 2.43 kg/kg, respectively; d = 1.33). Lastly, MQI_{ARMS + LEGS} was greater in NDS (2.89 ± 0.46 kg/kg, d = 0.97) than the DS group (2.25 ± 0.83 kg/kg). Individuals with DS exhibit lower HGS, ALM, and MQI compared to weight-matched peers without DS, underscoring the need for targeted interventions to improve muscle health.