Inflammatory bowel disease has a small effect on bone mineral density and risk for osteoporosis

A high prevalence of osteoporosis has been reported among individuals with inflammatory bowel disease (IBD). We performed a population-based analysis to determine whether IBD is itself a risk factor for low bone mineral density (BMD) or whether low BMD results from other factors associated with IBD.

We identified 1230 subjects with IBD in the Manitoba BMD Database, which contains results of BMD tests performed on all Manitobans since 1997 (n = 45,714). BMD was assessed at the lumbar spine (mean value, L1-L4), hip (total), femoral neck, and trochanter. Multivariate linear and logistic regression analyses were performed to determine the independent effects of IBD, Crohn's disease (CD), or ulcerative colitis (UC) on T score and the presence of osteoporosis (a low T score was equal to or less than -2.5) at any site; we controlled for age, sex, body mass index, hormone replacement therapy, osteoprotective medications, and corticosteroid use. We also performed regression analysis within the IBD population to determine the effect of IBD-specific factors on T score and osteoporosis.

IBD was associated with a statistically significant but small effect on T score; IBD did not increase the risk for osteoporosis at any site measured. CD was associated with an increased risk of osteoporosis at the lumbar spine and trochanter, but UC was not associated with an increased risk of osteoporosis or low T score. No IBD-specific variables were associated with increased risk of osteoporosis or low T score.

IBD has a small effect on BMD; CD poses a greater risk than UC. The risk of osteoporosis in patients with IBD appears to be related to other known osteoporosis risk factors.