A new study has reinforced the link between anorexia nervosa and reduced bone mineral density (BMD), especially in patients with lower body mass index.

“Our large study raises further concerns that [anorexia nervosa] has significant deleterious effects on BMD,” wrote Cassandra Workman, MD, of the Eating Recovery Center in Denver and coauthors. The study was published in Bone.

To determine the degree of low BMD in patients with certain severe eating disorders, the researchers reviewed the medical records of 336 patients with either anorexia nervosa–restricting subtype (AN-R) or anorexia nervosa–binge/purge subtype (AN-BP) who had been admitted to a treatment facility in Denver. Bone density was assessed using dual-energy x-ray absorptiometry, with osteopenia being diagnosed for an average BMD z score between –1.0 and –2.0 and osteoporosis being diagnosed for an average BMD z score of less than –2.0. The average age of the patients was 27 years (standard deviation, 9.12; range, 18-69), and 91% (n = 305) were women.

Across the sample, the average BMD z score was –1.67 (SD, 1.21), and 43.5% of the sample met the established criteria for low BMD.

Patients with AN-R had slightly lower z scores (–1.79; SD, 1.31), compared with patients with AN-BP (–1.54; SD, 1.08; P = .06), but the severity of osteoporosis was greater in patients with AN-R, compared with patients with AN-BP (chi-square, 7.40; P less than .01). Lower body mass index topped both anorexia nervosa subtype and duration of illness as a predictor of low BMD and probable osteoporosis (P less than .001).

The authors acknowledged their study’s limitations, including the use of retrospective data from the patient charts, which did not allow for assessment of follow-up improvements or longer-term effects. In addition, they noted that extrapolation of their findings may be problematic because all the patients were from a single site and the data might be representative of “a more ill population than a true cross section of the eating disorder population.”

The authors reported no conflicts of interest.

SOURCE: Workman C et al. Bone. 2019 Nov 23. doi: 10.1016/j.bone.2019.115161.