Predictors of bone mineral density reduction in adolescents with anorexia nervosa

Objectives: To determine which variables are associated with a significant reduction in bone mineral density (BMD) in adolescent anorexia nervosa and to establish guidelines for indication of bone densitometry. Method: One hundred seventy patients (treated from 1997 until 1999), aged 10 to 17 years, with a DSM-IV diagnosis of anorexia nervosa were evaluated by dual-energy-x-ray absorptiometry in the lumbar spine (L2-L4) and the femoral neck. The results were compared with the normative data for BMD values by age and sex in Spanish adolescents. Results: 44.1% of patients had osteopenia at the lumbar spine and 24.7% at the femoral neck. The following variables were related to osteopenia: more than 12 months since onset of the disorder (p < .001), more than 6 months of amenorrhea (p < .001), body mass index <15 (p < .001), calcium intake <600 mg/day (p < .01), and <3 hours/week of physical activity (p < .001). In a stepwise logistic regression analysis to predict reduced spinal BMD, 3 variables-months elapsed since the onset of weight loss, calcium intake, and body mass index-correctly classified 78.8% of patients. Conclusions: Adolescent anorexia nervosa patients with the characteristics outlined above are at high risk of reduced BMD, and densitometry is recommended to determine the degree of osteopenia.