Patients with inflammatory bowel disease (IBD) are at risk of low bone mineral density (BMD). The aim of this cross-sectional study was to investigate (i) whether patients with IBD in long-term remission have greater bone density relative to patients with active disease, (ii) the effect of remission on BMD in ulcerative colitis and Crohn's disease, and (iii) the effect of azathioprine treatment, used to induce remission, on BMD.
BMD relative to the age-standardised mean (Z-score) was measured by dual-energy X-ray absorptiometry at the left femoral neck and lumbar spine in consecutive patients with IBD. Patients were divided into the following groups: (i) active disease, (ii) remission of less than one year, (iii) remission of one to three years, and (iv) remission of more than three years. Active disease was defined as three or more bowel motions per day, treatment with oral or rectal corticosteroids, and/or presence of a fistula. The subgroups with ulcerative colitis and Crohn's disease and the effect of taking azathioprine were compared. All results were controlled for confounding variables. RESULTS A total of 137 (64 ulcerative colitis, 73 Crohn's disease) patients were evaluated. Patients in remission for more than three years had a normal mean Z-score that was significantly higher than those with active disease at both the femoral neck and the lumbar spine for both ulcerative colitis and Crohn's disease. Patients taking azathioprine and in remission had significantly higher mean Z-scores at the lumbar spine than patients with active disease and who were not taking azathioprine.
In patients with ulcerative colitis and Crohn's disease, age-matched BMD is higher with increasing duration of disease remission and induction of remission by azathioprine.