Background Body component change and functional decline are common problems in patients with COPD. Little was known about patients with dynapenia. This study intends to compare sarcopenia and dynapenia in patients with COPD.

Methods This study prospectively collected patients with stable spirometry confirmed COPD. Patients received body impedance analysis, handgrip strength, short physical performance battery, and six-minute walk evaluation. Dynapenia was defined by preserved fat free mass by Bioelectrical impedance analysis (M: ? 7.0 kg/m2, F: ? 5.7 kg/m2) but decreased handgrip strength (M: <28 kg, F: <18 kg) while sarcopenia entailing significant decrease in both dimensions.

Results Totally 377 patients completed all evaluations and were analyzed cross-sectionally. Patients were grouped into three categories: 81 (21.5%) patients in Dynapenia group, 87(23.1%) patients in Sarcopenia group and the remaining in General group. Dynapenia group patients have the highest BMI, and the highest body fat component among the three groups, but similar fat-free mass to General group patients. Both fat component and fat-free mass are severely reduced in sarcopenic patients. The degrees of symptoms became severe in a trend from General group, then Dynapenia group to Sarcopenic group (p<0.05). The mean 6-minute walk test and the percent of predicted value were 406.1m (84.2%), 344.6m (78.5%) and 289.2m (68.2%) for General, Dynapenia, and Sarcopenia groups, respectively (p<0.05).

Conclusions The clinical characteristics are extremely different in dynapenic and sarcopenic patients. They are two different extrapulmonary phenotypes that deserve attention when treating patients with COPD.