Clinical data and data on BMD are shown in . Ninety-eight percent of patients were white and 2% were Asian. Mean T-scores were −1.4 ± 0.1 SD for the anterior–posterior spine, −1.8 ± 0.1 SD for the lateral spine, and −1.4 ± 0.1 SD for the total hip. Twenty-six percent of patients (n = 34) reported a history of fracture (foot or ankle [n = 6], hand or wrist [n = 7], leg [n = 1], arm or elbow [n = 4], stress fracture [n = 5], and other fracture [n = 11]).
Clinical Characteristics of Study Patients and Comparison by Estrogen Use and Menstrual History*
Osteopenia and osteoporosis, respectively, were seen at the anterior–posterior spine in 50% and 13% of patients, at the lateral spine in 57% and 24% of patients, and at the total hip in 47% and 16% of patients. Normal BMD was seen at the anterior–posterior spine in only 37% of patients, at the lateral spine in 19% of patients, and at the total hip in 37% of patients. Results of lateral and anterior– posterior spinal tests of BMD were discordant in 36 patients, of whom 31 had normal BMD at the anterior– posterior spine (T-score−1.0) but low BMD at the lateral spine (T-score ≤ −1.0) (P < 0.001). Bone mineral density was reduced by at least 1.0 SD at one or more skeletal sites in 92% of patients and by at least 2.5 SD in 38% of patients. No differences in BMD were observed between patients with anorexia nervosa alone and patients with anorexia nervosa and concomitant bulimia nervosa (P < 0.05 at all sites; data not shown).
Twenty-three percent of patients were current estrogen users (mean duration, 25.3 ± 5.4 months) and 58% were previous estrogen users (mean duration, 23.9 ± 3.1 months). Bone mineral density did not differ at any site according to current or previous estrogen use (). Age, body mass index, and age at menarche were similar in the subgroup comparisons according to estrogen status. Oral contraceptives were used in all but 3 of the current estrogen users (10%) and all but 7 of the ever-estrogen users (10%); these 10 women received conjugated estrogen. Similar results were obtained in a subanalysis limited to the patients receiving oral contraceptives (data not shown). Total duration of estrogen use was not correlated with BMD at the anterior–posterior spine, lateral spine, femoral neck, total hip, trochanter, or total body (P > 0.10 for all comparisons). Patients with primary amenorrhea (n = 7) weighed less and had lower BMD at all sites than patients with secondary amenorrhea (n = 123) (), although sample size was small in the primary amenorrhea group. Total calcium intake was not correlated with BMD at any site (P > 0.1 for all sites). Fifty-seven percent of patients were receiving calcium supplements, 53% were receiving a multivitamin containing 400 IU of vitamin D, and 43% were receiving both. Bone mineral density did not differ in patients receiving nutritional supplements (data not shown).
Weight was a significant independent predictor of BMD at all skeletal sites (). Patients with normal BMD, osteopenia, and osteoporosis at the total hip weighed 48.7 ± 0.8 kg, 45.9 ± 0.8 kg, and 39.0 ± 0.7 kg, respectively. Similar trends were seen at other skeletal sites (data not shown). Age at menarche was a significant independent predictor of BMD measured by anterior–posterior spinal densitometry. Time since last menstrual period was a significant predictor of BMD at the anterior–posterior and lateral spine. Our results were similar when we used multivariate regression models with total duration of amenorrhea instead of last menstrual period in patients for whom this information was available (n = 78) (data not shown).
Univariate and Multivariate Regression Analyses*