Reduced bone mineral density in male rheumatoid arthritis patients: frequencies and associations with demographic and disease variables in ninety-four patients in the Oslo County Rheumatoid Arthritis Register

Abstract

Objective: To examine reductions in bone mineral density (BMD) and factors associated with reduced BMD in 94 male rheumatoid arthritis (RA) registry patients ages 20-70 years.

Methods: Dual-energy x-ray absorptiometry was used to measure BMD in the anteroposterior lumbar spine at L2-LA, the femoral neck, and the total hip, and clinical data were collected. The patients were recruited from a validated county RA registry (completeness 85%) comprising 192 men ages 20-70 years. Age-specific BMD values were compared with a pooled healthy European/United States population. Bivariate and multivariate analyses were performed to determine demographic and disease-related associations with BMD and reduced bone mass (Z score of < or =1 SD below the mean value in controls).

Results: A statistically significant BMD reduction was found only for the oldest age group (60-70 years): 5.2% reduction in the femoral neck and 6.9% in the total hip. No BMD reduction was found at L2-L4. The proportions (95% confidence intervals) of RA patients with Z scores of < or =1 SD below control (16% expected) were 30.9% (21.6-40.2) for L2-L4, 30.8% (95% CI 21.3-40.3) for the femoral neck, and 33.0% (95% CI 23.3-42.7) for the total hip. Disease activity and severity measures were, in general, not associated with BMD or reduced bone mass.

Conclusion: A 2-fold statistically significant increased frequency of patients with reduced bone mass (Z score of < or =1 SD below control; 16% expected) was found for both the spine and the hip. The only significant reduction in BMD by age group was for the hip in patients who were ages 60-70 years, with no reduction in L2-LA BMD. Multivariate analyses did not reveal consistent associations between reduced BMD and demographic or disease variables.