Relationship between bone mineral density and duration of rheumatoid arthritis

BackgroundLonger disease duration is believed to be associated with more pronounced bone loss in rheumatoid arthritis (RA). This study was designed to assess bone mineral density (BMD) status in RA compared with age-matched control in relation to disease duration.MethodsThis study included 177 RA and 283 age-matched non-RA controls. BMD at the femoral neck and lumbar spine was assessed by Dual Energy X-ray Absorptiometry Osteoporosis was diagnosed according to WHO criteria. We divided patients with RA into groups based on disease duration of <2, 2–5, 5–10, and >10 years and compared them with controls. The relationship between disease duration and BMD was investigated by chi square and Spearman test.ResultsMean age of patients and control subjects was 51.2 ± 12.5 and 52.2 ± 6.7 years, respectively and mean disease duration was 86.5 ± 73.3 months. Osteoporosis at the femoral neck and lumbar spine in patients with RA was significantly higher than in controls. Femoral neck BMD in RA was negatively correlated with disease duration and 4.5% variations of femoral neck BMD was explained by disease duration (r² = 0.045, P = 0.005). Odds Ratio (OR) for osteoporosis in RA patients as compared to controls was increased by prolongation of disease duration from 2.38 (0.38–14.7) in patients with disease duration <2 years to 12.56 (2.24–70.2) in patients with disease duration >10 years. For patients treated with methotrexate compared to those who had never received methotrexate the odds ratio for femoral neck osteoporosis reduced by 64% (OR = 0.36, 95% CI, 0.15–0.91).ConclusionThere is a significant negative relationship between femoral neck BMD and disease duration in RA. The value of OR increases proportionately with lengthening of disease duration which can be reduced significantly by methotrexate therapy.