Gender and skeletal muscle characteristics in subjects with chronic obstructive pulmonary disease

Summary Background The influence of gender in the clinical expression of COPD has received important attention. Limited information exists regarding gender differences in the skeletal muscle characteristics in COPD subjects. The present study was aimed to determine the differences in the skeletal muscle characteristics in men and women with and without COPD. Methods For comparison we studied 24 female (61 ± 9 years) and 30 male (65 ± 8 years) COPD patients with similar disease severity. In addition healthy subjects, 17 women (58 ± 8 years), and 9 men (57 ± 8 years) were studied. Pulmonary function, health status, six minute walk distance test (6MWD) and vastus lateralis muscle biopsy were assessed. Fiber type proportion, fiber type cross sectional area (CSA), capillary counts, and activity of citrate synthase (CS), 3-hydroxyacyl-CoA-dehydrogenase (HAD) and lactate-dehydrogenase (LDH) were determined. Results Pulmonary function, health status and 6MWD were similar in male and female COPD patients. Fiber type distribution was similar between women (I = 42 ± 9%, IIA = 39 ± 13%, IIX = 19 ± 7%) and men (I = 39 ± 13%, IIA = 38 ± 9%, IIX = 29 ± 10%) with COPD, as well as CSA, capillarity and enzymes (CS 8.59 ± 1.6 vs.9.74 ± 2.6, HAD 9.03 ± 1.9 vs. 9.84 ± 2.5, LDH 124 ± 48 vs. 151 ± 68 μmol min −1  g −1 ). In normal subjects a decrease in type IIX fibers CSA was found in women compared with men (3703 ± 1478 vs. 5426 ± 1386 μm 2 , respectively). Conclusions Female and male with COPD have similar skeletal muscle characteristics; it is possible that the disease blurs the gender differences. On the other hand, there seems to be fewer differences in muscle characteristics between older men and women, perhaps due to lower male testosterone levels and physical inactivity.