Abstract
Conventional wisdom suggests that children who develop inflammatory bowel disease are at particularly increased risk of osteopenia and osteoporosis because of the effects of disease activity, nutritional factors and medications, especially glucocorticoids, during critical periods of bone growth. In this study, Bernstein et al endeavoured to determine the prevalence of reduced bone mineral density (BMD) in a population-based cohort of women with onset of inflammatory bowel disease (IBD) before 20 years of age. A secondary goal of the study was to compare estimates of the rates of osteopenia and osteoporosis using two different techniques: the more conventional areal BMD and volumetric BMD. The latter measure is designed to account for the reduction in bone size that can occur because of growth delay associated with childhood IBD. On the other hand, areal BMD is said to underestimate true bone density. The authors identified a cohort of patients using their research registry of IBD patients in Manitoba. Women who developed IBD before 20 years of age and who were younger than age 45 at the time of the study were invited to complete a questionnaire and undergo dual energy x-ray absorptiometry (DEXA). Of the 148 subjects who were approached, 70 were eligible and agreed to participate. More than 80% of the participating subjects had Crohn's disease (CD) and more than 80% affected had onset of disease after puberty. BMD did not appear to differ between the patients with prepubertal and those with postpubertal onset. Twenty-five of the 70 subjects had an areal T score less than -1 at one or more site. Only three had osteoporosis (T score less than -2.5). Individuals with a T score less than -1 had lower body weight and were more likely than other patients to have experienced amenorrhea in the year prior to DEXA testing. When T scores were adjusted for abnormalities in bone size, the mean volumetric T score was slightly but statistically significantly higher than the corresponding areal T score at each site.