Factors influencing bone loss in rheumatoid arthritis: a longitudinal study

Abstract

Objectives: To assess the occurrence of bone loss in rheumatoid arthritis (RA) and to determine 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 was 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 the 0 and 18-month investigations. Bone turnover was assessed at baseline by measuring the serum levels of 4 biological markers. Three of them reflected bone formation, i.e., procollagen type I C-terminal propepeptide (PICP), procollagen type I N-terminal propeptide (PINP) and osteocalcin (OC). The fourth, procollagen type I-C terminal telopeptide (ICTP), reflected bone resorption. Bone mineral density (BMD) was measured by dual energy X-ray absorptiometry both at the lumbar spine (LS) and femoral neck (FN) at baseline and 18 months later.

Results: Bone loss occurred both at the LS: 2.1%, [95% CI: 0.8%-3.4%, P < 0.005] and femoral neck: 3.1%, [95% CI: 1.1%-5.1%, P < 0.005]. Bone loss was markedly 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 between 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 only (r = 0.34, P < 0.05). Fast losers (bone loss at the LS above the median) had higher OC (P < 0.01) and ESR (P < 0.05) levels at baseline as compared with 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.