Prevalence and pathogenesis of osteoporosis in patients with inflammatory bowel disease

Decreased bone mineral density is a frequent finding in patients with inflammatory bowel disease. Factors contributing to this are: 1) malabsorption of vitamin D, calcium and possibly vitamin K and other nutrients, 2) treatment with corticosteroids, 3) inflammatory cytokines in inflammatory bowel disease, and 4) hypogonadism induced by the inflammatory bowel disease. Among patients with Crohn's disease from 32% to 38% have osteopenia (Z-scores <-1), and among patients with ulcerative colitis 23% to 25% have osteopenia. The mean deficit was 0.44+/-0.08 Z-scores in the spine in Crohn's disease and 0.34+/-0.08 in ulcerative colitis. A similar deficit was seen in the hip in both conditions. From these deficits, an increase in overall fracture risk of 1.1-1.3 should be expected. The observed excess fracture risk was limited compared to the general population in both Crohn's disease (RR=1.2, 95% CI: 0.9-1.6 for any fracture and 2.2, 95% CI: 1.2-4.0 for spine fractures) and ulcerative colitis (RR=1.1, 95% CI: 1-1.2 for any fracture, and 1.5, 95% CI: 0.9-2.5 for spine fractures). The observed excess fracture risk was close to that expected from the changes in BMD. Despite the limited excess fracture risk, a relatively large percentage of all fractures may be attributable to corticosteroid use among users of corticosteroids.