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.

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.