Background: Studies have shown an association between inflammatory bowel disease (IBD) and low bone density. Previous publications, however, measured only a single parameter, either T or Z score, making comparison of data difficult.
Objective: To assess the effect of disease factors on both T and Z scores in a population of patients with IBD.
Methods: Risk factors for development of low bone density were recorded in IBD patients with confirmed diagnosis and disease extent. Bone density was then measured at the spine and neck of femur using dual-energy X-ray absorptiometry.
Results: Ninety-one patients (49 male, 42 female) with a mean age of 46.6 years (range 22-84) were studied. Forty-eight patients had ulcerative colitis and 43 had Crohn's disease. Mean Z scores were -0.60 at the hip and -0.61 at the spine, whilst mean T scores were - 1.61 at the hip and -1.15 at the spine. Univariate analysis of Z scores identified Crohn's disease, high steroid use and low BMI as significantly associated with low bone density. An identical analysis using T scores failed to show any significant relationships. On multivariate analysis of Z scores, only disease type and BMI remained significant.
Conclusions: Low bone density is associated with IBD particularly in patients with Crohn's disease and low BMI. This large UK study is the first to report both T and Z scores in patients with IBD and shows that Z scores are the most reliable guide to the effect of IBD on bone density.