Background It is widely accepted that patients with rheumatoid arthritis (RA) lose bone mass more rapidly those without such history over time due to a number of factors including systemic inflammation and corticosteroid use. It is, however, not known whether peak bone mass is affected by rheumatoid arthritis. Quantifying bone loss in such patients will help to inform fracture prevention strategies and may indicate the need for lowering the threshold for intervention.
Objectives To investigate the peak bone mass and subsequent change in bone mass over time in patients with rheumatoid arthritis compared to patients without such history attending for multiple routine dual-energy X-ray absorptiometry (DXA) scans.
Methods Patients referred for two or more dual-energy X-ray absorptiometry (DXA) scans at the Rheumatology outpatient department at a district general hospital in the North West of England between June 2004 and August 2012 were identified and their data were included in the analysis. Information collated on these patients included age at scan, bone mass at the femoral neck, total femur and lumbar spine and history of rheumatoid arthritis. Other risk factors for osteoporosis were also identified. Linear mixed effects models were constructed to longitudinally predict peak bone mass and change over time in patients with and without RA from the age of 30 years, identifying and defining the significance of a history of rheumatoid arthritis on bone mass at the three anatomical sites.
Results During the study period, 1,353 patients had a total of 2,775 DXA scans. Of these patients, 131 individuals with a history of rheumatoid arthritis had a total of 268 DXA scans.
Of the RA patients, 79% were female and the median age at first scan was 69.0 years (interquartile range 60.3 to 76.8 years). The median interval between scans was 3.1 years (interquartile range 2.7 to 3.9 years).
At the femoral neck, a history of rheumatoid arthritis was not significant to the peak bone mass (p>0.05) or change in bone mass over time (p>0.05). This was also the case for the lumbar spine site.
At the total femur, a history of rheumatoid arthritis was significant to both the peak bone mass (p<0.001) and change in bone mass over time (p<0.001). Peak bone mass achieved was significantly higher in those with rheumatoid arthritis, however these subjects lost bone mass at a rate twice that of those without such history.
Conclusions These results echo the literature suggesting that RA patients lose bone at a significantly higher rate than those without such history, although this study did not find consistency between all anatomical sites. Despite having significantly higher peak bone mass - which may be explained by increased local bone degeneration or unmeasured confounders - this rate of bone loss places RA patients at a substantially higher risk of fracture than the normal population. These results strongly support a lower threshold for initiating bone protective measures in RA patients and highlight the importance of further research.
Disclosure of Interest None declared
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