Background Women with Ankylosing Spondylitis (AS) seem to be less responsive to TNF-α blockers and have a shorter drug survival. This might be explained by differences in body composition (BC), as women have higher total body fat (BF).
Objectives Assess the relationship between gender, BC and response to TNF-α blocker treatment in a cohort of TNF-α blocker naïve AS patients.
Methods AS patients (Modified New York criteria), ≥18 years old, who had a Dual-Energy X-ray Absorptiometry BC analysis before the start of TNF-α treatment and at least 6 months thereafter were included. Demographic information and the disease activity measures ASDAS CRP and BASDAI were reported. Fat Mass (FM) was reported as BF% (FM/Total body mass), and Fat Mass Index (FMI= FM kg/height m2). Fat Free Mass (lean mass + bone mineral content) was reported as its index (FFMI kg/m2). BF%, FMI, and FFMI percentiles, according to the reference population tables, stratified by age and gender, were also reported.
Results Forty-one patients were included, 61% were men. Demographic characteristics were similar in men and women. The FFMI percentile was remarkably low in men, probably reflecting muscle wasting (figure 1). The percentiles increased in men and decreased in women after treatment. The clinically important improvement (CII) of ASDAS CRP was achieved by 52% of men and only 37.5% of women. The minimum CII for BASDAI was achieved by 64.7% of men, and only 35.7% of women that had a BASDAI ≥4 at baseline. After multivariate analysis we found a significant relationship between higher BF%, FMI or FMI percentile at baseline and a lower chance of achieving at least a CII of ASDAS CRP; the same relationship was found between FMI percentile at baseline and the minimum CII for BASDAI (table 1).
Conclusions Higher body fat content at baseline is independently associated with a worse response to treatment with TNF-α blockers, measured by ASDAS-CRP and BASDAI change, and might contribute to the lower response to treatment rates in female patients. Also, there is a trend toward muscle mass recovery in male patients after treatment with TNF-α blockers.
Acknowledgements This study was endorsed by an ASAS (Assessment of SpondyloArthritis international Society) Fellowship.
Disclosure of Interest None declared
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