Impact of Lean and Fat Mass on Disease Activity and Function in Spondyloarthritis

Changes in body mass composition, such as reduced lean and fat mass, can occur in a patient with rheumatic diseases. However, data about body composition in spondyloarthritis (SpA) showed conflicting results. The aim of the present study was to assess by DXA the distribution of lean and fat mass in SpA patients compared to healthy controls and to investigate the association between body mass composition and disease characteristics.

We conducted a cross-sectional case-control study including 50 SpA patients and 50 controls. Sociodemographic data, as well as disease characteristics, were assessed. Body composition measurements and biochemical and inflammatory serum markers were evaluated. Radiographic data (Bath Ankylosing Radiologic Index and the modified Stroke Ankylosing Spondylitis Spine Score) was also recorded.

No statistically significant correlation was found between the two groups regarding bone mineral density and body mass distribution. However, a lower weight was observed in the study group compared to the control group (p = 0.043). Male gender and younger age were associated with a higher lean mass (p = 0.05). C-reactive protein (CRP) level was positively correlated with lean mass (r = 0.38, p = 0.023). Similarly, BASFI was higher in patients with lower fat mass (r = -0.42, p = 0.024). A longer duration of NSAIDs intake was associated with a lower lean mass and a higher fat mass. However, no correlations were found between body mass composition and BASRI mSASSS scores as well as bone mineral density and calcium intake.

Our findings suggest that younger age, male gender, and axial phenotype were associated with higher lean mass.