Advanced Age and Lower BMI Associated With Reduced Bone Mineral Density Among Patients with IIM

Patients with idiopathic inflammatory myopathies (IIM) exhibited a higher prevalence of reduced bone mineral density (BMD) compared against patients with nonrheumatological conditions, according to study results published in Therapeutic Advances in Musculoskeletal Disease.

Investigators conducted a single-center, case-control study to assess and compare the occurrence of and risk factors for reduced BMD among patients with IIM and a nonrheumatological control group.

Patients diagnosed with IIM according to 2017 European League Against Rheumatism/American College of Rheumatology classification criteria were age- and sex-matched 1:1 with patients with nonrheumatological conditions. Additionally, the BMD results of female patients with IIM were compared against those of age-matched female patients with rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE).

Reduced BMD was defined as osteopenia or osteoporosis at the lumbar spine or neck of the femur.

A total of 230 patients were included in the analysis: 65 patients with IIM, 65 patients in the nonrheumatological control group, 50 patients with RA, and 50 patients with SLE.

Among patients with IIM, the average age was 58.6+11.0 years and 50 (76.9%) patients were women. There were no significant differences observed between the 2 groups in terms of smoking, drinking habits, menopausal status, and comorbidity status.

Reduced BMD, osteopenia, and osteoporosis were present among 73.8%, 44.6%, and 29.2% of patients with IIM vs 56.9%, 43.1%, and 13.8% of patients in the nonrheumatological control group, respectively.

The prevalence of reduced BMD (P =.043) and osteoporosis (P =.033) was significantly higher among patients with IIM vs the nonrheumatological control group.

Results of the multivariate analysis revealed that IIM was independently correlated with reduced BMD (odds ratio, 2.12; P =.048; 95% CI, 1.01-4.46).

The median major osteoporotic fracture scores were 8.05% among the IIM group vs 3.75% among the nonrheumatological control group (P =.005).

Among patients with IIM, advanced age and lower body-mass index were associated with reduced BMD at the hip (P <.001 and P =.003) and lumbar spine (P =.006 and P =.001), respectively.  

Among female patients with IIM, 38 women (76%) had reduced BMD, consistent with the 38 (76%) women in the RA group. A total of 31 women (62%) in the SLE group had reduced BMD (P =.205).

Among study limitations, the investigators only assessed BMD, which does not provide a comprehensive reflection of actual bone quality. Additionally, the analysis was underpowered to detect differences in the pervasiveness of fragility fractures between each group. Finally, selection bias due to the retrospective nature of the analysis cannot be ruled out.

The study authors concluded, “Vigilant monitoring of BMD and timely initiation of bone protective therapies should be considered in IIM patients, especially those who are at advanced age and underweight.”