Background Sarcopenia is a syndrome characterized by progressive loss of skeletal muscle mass, which results in decreased muscle strength and impairment of physical and functional capacity. There are no data regarding this disorder in AS patients and the possible beneficial effect of anti-TNF therapy in this complication.

Objectives To determine the longitudinal anti-TNF induced changes in the frequency of sarcopenia and in body composition of AS patients.

Methods Thirty active AS patients (24 men and 6 women) were assessed at baseline (BL), 6 (6M), 12 (12M) and 24 months (24M) after anti-TNF therapy. Patients were evaluated for clinical parameters (BASDAI, BASFI, BASMI, ASQol) and inflammatory markers (ESR, CRP). Physical activity remained stable during the study. Body weight and Body Mass Index (BMI) were also measured. Fat mass (FM), total lean mass (LM) and appendicular lean mass (ASM = sum of arms and legs) were analyzed by dual-energy X-ray absorptiometry (DXA). Sarcopenia was defined when the relative skeletal muscle mass index (RSMI= ASM/height²) was less than 7.26 kg/m²for men and 5.45 kg/m²for women (Baumgartner’s criteria).

Results Sarcopenia was found in 16.6% of AS patients. There was a significant decrease in the frequency of sarcopenia with a complete reversion in all patients at 24 months (BL: 16.6% vs. 6M: 13.3% vs. 12M: 6.6% vs. 24M: 0%, p<0.001). This finding was paralleled by an increase of body weight (BL: 72.65 kg vs. 6M: 73.87 kg vs. 12M: 74.65 kg vs. 24M: 75.01 kg, p=0.007), BMI (BL: 25.66 kg/m² vs. 6M: 26.07 kg/m² vs. 12M: 26.34 kg/m² vs. 24M: 26.90 kg/m², p=0.038) and total lean mass (BL: 52.56 kg vs. 6M: 53.19 kg vs. 12M: 54.08 kg vs. 24M: 54.01 kg, p≤0.001), particularly in the first 12 months of therapy (BL vs. 12 months, p<0.05). No difference was observed in fat mass (BL: 17.79 kg vs. 6M: 18.10 kg vs. 12M: 18.14 kg vs. 24M: 18.90 kg, p=0.07) and percentage of fat mass (BL: 24.14% vs. 6M: 24.27% vs. 12M: 54.08% vs. 24M: 24.86%, p=0.146). BASDAI (BL: 5.11 vs. 6M: 2.79 vs. 12M: 2.79 vs. 24M: 2.57, p<0.001), BASFI (BL: 5.40 vs. 6M: 2.97 vs. 12M: 2.86 vs. 24M: 2.41, p<0.001), BASMI (BL: 4.07 vs. 6M: 3.23 vs. 12M: 3.07 vs. 24M: 3.00, p=0.001) and ASQoL (BL: 10.03 vs. 6M: 6.43 vs. 12M: 6.40 vs. 24M: 5.80, p<0.001) improved during study period, with asignificant reduction in ESR (BL: 23.75 mm/h vs. 6M: 8.17 mm/h vs. 12M: 7.30 mm/h vs. 24M: 9.87 mm/h, p<0.001) and CRP levels (BL: 37.03 mg/L vs. 6M: 3.36 mg/L vs. 12M: 7.22 mg/L vs. 24M: 5.32 mg/L, p<0.001) after TNF therapy.

Conclusions The novel demonstration of anti-TNF induced recovery in sarcopenia reinforces its beneficial effect in muscle mass and functional capacity in AS patients, most likely associated with inflammation resolution.

1. Baumgartner RN, Koehler KM, Gallagher D, Romero L, Heymsfield SB, Ross RR et al (1998) Epidemiology of sarcopenia among the elderly in New Mexico. Am J Epidemiol 147:755-63

Disclosure of Interest None Declared