Background: Bone mineral density (BMD) is known to be lower in patients with systemic sclerosis (SSc) compared to the background population especially in women, but the underlying factors are not entirely understood.

Objectives: The first aim is to explore the known risk factor of low bone density in subgroups of SSc patients with normal BMD, T-scores <-1.00 ─ >-2.5 or T-score of ≤-2.5 in relation to sex and compared to controls. In addition, we want to explore the effect of these factors in SSc patients compared to controls, to predict the subgroup after adjusting for confounders like age, sex, menopause and BMI.

Methods: In total, 211 SSc patients, 182 women and 29 men (mean age 61.4 (SD 13.4) years and mean disease duration 9.2 (SD 8.0) years) regularly followed at the Rheumatology Department, Skåne University Hospital in Lund, Sweden and 505 age and sex matched controls from the same catchment area were included. Data on BMD performed using DXA, BMI, a questionnaire regarding potential risk factors for low BMD and blood samples were collected in both patients and controls. Multinomial logistic regression analysis was used to calculate odds ratio (OR) for having low BMD with a T-scores <-1.00 ─ >-2.5 or T-score of ≤-2.5. Since the missing data in variables used in this study were <4%, the Random Forest was employed for the imputation.

Results: Compared to individuals with normal BMD, women (both patients and controls) with T-score ≤-2.5 were older, hade lower BMI and were more likely to be in menopause (Table 1). There were no significant effects of several other traditional risk factors for low BMD such as smoking status, usage of corticosteroids for more than three months, history of first degree relative with hip fracture or physical activity >2.5 h/week (excluding walks). Higher CRP had an increased OR for the lowest BMD (T-score ≤-2.5); p=0.05 and less sufficient exercise (defined as <2.5 h/week excluding walks) predicted lower BMD (T-scores <-1.00 ─ >-2.5) in patients, p=0.047 (Table 2). CRP and exercise had no significant effect on BMD for controls.

Conclusion: In this cohort of patients with established SSc, the traditional risk factors such as higher age, lower BMI and being in menopause were confirmed as risk factor for decreased BMD. However, after adjustment for sex, age, menopause and BMI other risk factors including daily use of corticosteroids, family history of hip fracture or smoking status had no impact on the lower BMD. However, higher marker of inflammation measured with CRP, less sufficient exercise defined as <2.5 h/week excluding walks predicted lower BMD in patients but not in controls.

REFERENCES: NIL.

Acknowledgements: Thanks are extended to funders and the research staff at the Clinical and Molecular Osteoporosis Research Unit, Malmö and staff at the Rheumatology Department at Skåne University Hospital, Lund. In memoriam of Fiona McGuigan.

Disclosure of Interests: Kerstin Lillpers: None declared, Morteza Najibi: None declared, Kristofer Andréasson: None declared, Roger Hesselstrand Employee at Boehringer Ingelheim, Kristina Åkesson Amgen, Astellas Pharma, Chugai and UCB, Meliha C Kapetanovic: None declared.

© The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.