Disease activity and severity in early inflammatory arthritis predict hand cortical bone loss

OBJECTIVES To determine the influence of disease-related variables on hand cortical bone loss in women with early inflammatory arthritis (IA), and whether hand cortical bone mass predicts subsequent joint damage. METHOD Adults aged ≥ 16 years with recent onset of IA were recruited to the Norfolk Arthritis Register between 1990 and 1998, and followed prospectively. At baseline, patients had their joints examined for swelling and tenderness and had CRP and disease activity 28-joint assessment score (DAS-28) measured. Radiographs of the hands were performed in a subgroup of patients at Year 1 and at follow-up, which were assessed using digital X-ray radiogrammetry (DXR). They were also evaluated for the presence of erosions using Larsen's method. Linear mixed models were used to investigate whether disease-related factors predicted change in DXR-areal bone mineral density (BMD(a)). We also evaluated whether DXR-BMD(a) predicted the subsequent occurrence of erosive disease. RESULTS Two hundred and four women, mean (s.d.) age 55.1 (14.0) years, were included. Median follow-up between radiographs was 4 years. The mean within-subject change in BMD(a) was 0.024 g/cm(2) equivalent to 1% decline per year. After adjustment for age, height and weight, compared with those within the lower tertile for CRP, those in the upper tertile had greater subsequent loss of bone. This was true also for DAS-28 and Larsen score. Among those without erosions on the initial radiograph (121), DXR-BMD(a) at baseline did not predict the new occurrence of erosions. CONCLUSION Increased disease activity and severity are associated with accelerated bone loss. However, lower BMD(a) did not predict the new occurrence of erosive disease.