Background Secondary osteoporosis is a comorbidity of Rheumatoid Arthritis (RA). Previous studies have suggested that biological therapies may reduce the rate of generalized bone loss in RA. Most of them focus on the short-term effect of Tumor Necrosis factor alpha (TNFα) inhibitors while the long-term effect of biological therapies is rarely studied.

Objectives Our primary aim was to analyze the long-term effect of biological therapies on bone mineral density (BMD) for RA patients compared to patients treated by synthetic DMARD over an 8-year follow-up.

Methods Patients were selected from a prospective, observational cohort of RA patients meeting the ACR/EULAR 2010 settings in Nice University Hospital between 2001 and 2016. BMD was assessed before the introduction of the biological therapy and during the follow-up. Two groups were studied: patients treated by biological therapies (TNFα inhibitors, Tocilizumab, Abatacept, Rituximab or Anakinra) and patients treated by synthetic DMARD only. Demographic, disease and treatment data were collected at each visit and BMD of the lumbar spine, femoral neck and total hip were assessed using dual energy X-ray absorptiometry (DXA) at baseline and after 1, 2, 3, 5 and 8 years.

Results A total of 181 patients with active RA starting a biological therapy were included versus 131 patients treated by synthetic DMARD. In both groups, the BMD of the lumbar spine, femoral neck and total hip remained stable after a 2-year follow-up (respectively -0.37%, p=0.66 versus +0.02%, p=0.83, -3.70%, p=0.77 versus -5.35%, p=0.74 and -3.31%, p=0.45 versus -4.84%, p=0.16), while a significant bone loss was found between initial measurement and 3, 5 and 8 -year- follow-up at femoral neck and total hip level. There was no significant difference between patients whether treated by biological or non-biological DMARD neither over the 0–1-year period nor over the 0–2, 0–3, 0–5 and 0–8-periods. Bone loss in patients treated by Tocilizumab were statistically lower at femoral neck level compared with TNFα inhibitors (p=0.02), Abatacept (p=0.02) and Rituximab (p=0.02), but also at total hip level, in comparison with TNF α inhibitors (p=0.05) and Abatacept (p=0.05).

Conclusions This study is the first to assess the effects of biological RA therapies as compared to synthetic DMARD ones. It highlights the protective effect of both biological and non-biological DMARD on bone loss during the first two years of treatment with no significant difference between them. Our results suggest that the effects of RA treatments depend on the inflammatory and disease activity which must be monitored clearly. Tocilizumab seems to be more effective than the other biological therapies, but further studies are necessary to confirm or infirm this tendency.

Disclosure of Interest None declared