Factors influencing bone loss in rheumatoid arthritis: A longitudinal study

Objectives To assess the occurrence of bone loss in rheumatoid arthritis (RA) and to d etermine the factors influencing bone loss (particularly the usefulness of bone turnover markers) over an 18-month period. Methods A total of 51 patients were studied, 6 men and 45 females (of whom 35 were menopausal). Their mean age was 56 +/- 10 years and the mean RA duration wa s 12 +/- 10 years. Twenty-eight (55%) were receiving corticosteroids (10 mg /day for a mean duration of 6 +/- 5 years). Several clinical and biological parameters reflecting disease activity or severity were recorded both at t he 0 and 18-month investigations. Bone turnover was assessed at baseline by measuring the serum levels of 4 biological markers. Three of them reflecte d bone formation, i.e., procollagen type I C-terminal propepeptide (PICP), procollagen type I N-terminal propeptide (PINP) and osteocalcin (OC), The f ourth, procollagen type I-C terminal telopeptide (ICTP), reflected bone res orption. Bone mineral density (BMD) was measured by dual energy X-ray absor ptiometry both at the lumbar spine (LS) and femoral neck (FN) at baseline a nd 18 months later. Results Bone loss occurred both at the LS: 2.1%, [95% CI: 0.8% - 3.4%, P < 0.005] a nd femoral neck: 3.1%, [95% CI: 1.1% - 5.1%, P < 0.005]. Bone loss was mark edly increased for postmenopausal women at the FN: 5.3% [95% CI: 2.9% - 7.6 %, P < 0.005]. Bone loss was not statistically significantly different betw een users and non-users of steroids. Bone loss at the LS was significantly correlated with both osteocalcin (r = 0.51, P < 0.01) and ICTP levels (r = 0.32, P < 0.05). FN bone loss was correlated with the osteocalcin level onl y (r = 0.34 P < 0.05). Fast losers (bone loss at the LS above the median) h ad higher OC (P < 0.01) and ESR (P < 0.05) levels at baseline as compared w ith slow losers (bone loss at the LS below the median). Conclusion Bone loss occurs in RA particularly at the FN and seems to be influenced by increased bone turnover and high levels of inflammation.