Bone mineral density and fractures in patients with rheumatoid arthritis: the DXA-HIP project

Objectives RA is a chronic disabling disease affecting 0.5-1% of adults worldwide. People with RA have a greater prevalence of multimorbidity, particularly osteoporosis and associated fractures. Recent studies suggest that fracture risk is related to both non-RA and RA factors, whose importance is heterogeneous across studies. This study seeks to compare baseline demographic and DXA data across three cohorts: healthy controls, RA patients and a non-RA cohort with major risk factors and/or prior major osteoporotic fracture (MOF).Methods This is a cross-sectional study using data collected from three DXA centres in the west of Ireland from January 2000 to November 2018.Results Data were available for 30 503 subjects who met our inclusion criteria: 9539 (31.3%) healthy controls, 1797 (5.9%) with RA and 19 167 (62.8%) others. Although age, BMI and BMD were similar between healthy controls, the RA cohort and the other cohort, 289 (16.1%) RA patients and 5419 (28.3%) of the non-RA cohort had prior MOF. In the RA and non-RA cohorts, patients with previous MOF were significantly older and had significantly lower BMD at the femoral neck, total hip and spine.Conclusion Although age, BMI and BMD were similar between a healthy control cohort and RA patients and others with major fracture risk factors, those with a previous MOF were older and had significantly lower BMD at all three measured skeletal sites. Further studies are needed to address the importance of these and other factors for identifying those RA patients most likely to experience fractures. What does this mean for patients?Rheumatoid arthritis (RA) is a disabling disease affecting millions of people worldwide. This disease causes pain, disability and other problems. RA affects not only joints (e.g. hip, knee, wrist), but also the bones, lungs, eyes and other body tissues. International studies show that people with RA are almost three times as likely to break a bone as the general population. Experts conclude that this is because of bone loss from the inflammation in RA. We measure bone mineral density (BMD) to manage osteoporosis in clinical practice with a test known as a DXA scan. People with lower BMD are more likely to break bones, causing further suffering and illness. In this study, we found that Irish patients with RA are much more likely to have fractures. An especially interesting finding in our study is that although the RA patients had similar age and BMD to healthy controls, far more of them had fractures. However, those with broken bones had lower BMD than those without, whether they had RA or not. Our findings suggest that more research is needed to gain a better understanding of why RA patients are prone to fractures, in order to prevent fracture occurrence in future.