Changes in bone density in patients with ankylosing spondylitis: A two-year follow-up study

The objectives of the study were to determine the 2 year rate of bone chang es in patients with ankylosing spondylitis (AS) and, whether bone loss is r elated to physical impairment, systemic inflammation, and therapy. Consecut ive outpatients fulfulling the modified New York criteria for AS were inclu ded. Baseline assessment included age, disease duration, treatment, clinica l, radiologic and laboratory data. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were determined every 6 months. Persistent system ic inflammation was defined as mean ESR greater than or equal to 28 mm/h or mean CRP greater than or equal to 15 mg/l. Bone mineral density (BMD) at t he lumbar spine and femoral neck was measured by dual-energy X-ray absorpti ometry, at baseline and year 2. Statistical analysis compared the baseline and 24 month follow-up BMD data, and determined whether baseline data, and persistent systemic inflammation during the 2 years, were related to the 24 month percentage changes in BMD. Fifty-four patients (35 men, 19 women; me an age 37.3 +/- 11.3 years, mean disease duration 12.4 +/- 8.6 years) were included. After 2 years, BMD did not change at the lumbar spine (+0.75% +/- 3.5, p = 0.23), and decreased at the femoral neck (-1.6% +/- 4, p = 0.006) . The 24 month percentage change in femoral neck BMD was related to persist ent systemic inflammation, defined using ESR (mean percentage change -4.1% +/- 5.7 and - 1.2% +/- 3.9 in patients with and without persistent inflamma tion; respectively; p = 0.007). These results suggest that persistent infla mmation might be an etiologic factor of bone loss in AS.