Bone mineral density and estimated hip strength in men with anorexia nervosa, atypical anorexia nervosa and avoidant/restrictive food intake disorder

Abstract

Objective: Few bone mineral density (BMD) data are available in men with anorexia nervosa (AN), and none in those with atypical AN (ATYP) (AN psychological symptoms without low weight) or avoidant/restrictive food intake disorder (ARFID) (restrictive eating without AN psychological symptoms). We investigated the prevalence and determinants of low BMD and estimated hip strength in men with these disorders.

Design: Cross-sectional: two centres.

Patients: A total of 103 men, 18-63 years: AN (n = 26), ARFID (n = 11), ATYP (n = 18), healthy controls (HC) (n = 48).

Measurements: Body composition, BMD and estimated hip strength (section modulus and buckling ratio) by DXA (Hologic). Serum 25OH vitamin D was quantified, as was daily calcium intake in a subset of subjects.

Results: Mean BMI was lowest in AN and ARFID, higher in ATYP and highest in HC (AN 14.7 ± 1.8, ARFID 15.3 ± 1.5, ATYP 20.6 ± 2.0, HC 23.7 ± 3.3 kg/m² ) (P < 0.0005). Mean BMD Z-scores at spine and hip were lower in AN and ARFID, but not ATYP, than HC (postero-anterior (PA) spine AN -2.05 ± 1.58, ARFID -1.33 ± 1.21, ATYP -0.59 ± 1.77, HC -0.12 ± 1.17) (P < 0.05). 65% AN, 18% ARFID, 33% ATYP and 6% HC had BMD Z-scores <-2 at ≥1 site (AN and ATYP vs HC, P < 0.01). Mean section modulus Z-scores were lower in AN than HC (P < 0.01). Lower BMI, muscle mass and vitamin D levels (R = 0.33-0.64), as well as longer disease duration (R = -0.51 to -0.58), were associated with lower BMD (P < 0.05).

Conclusions: Men with AN, ARFID and ATYP are at risk for low BMD. Men with these eating disorders who are low weight, or who have low muscle mass, long illness duration and/or vitamin D deficiency, may be at particularly high risk.

Keywords: anorexia nervosa; bone density; feeding and eating disorders; vitamin D deficiency.

FIGURE 1

(A) Mean bone mineral density (BMD) Z-scores at the postero-anterior (PA) spine and total hip were lower in men with anorexia nervosa (AN) and avoidant/restrictive food intake disorder (ARFID) compared to healthy controls (HC). (B) The prevalence of any BMD Z-score <−1 was higher in AN than HC, while the prevalence of any BMD Z-score <−2 was higher in AN and ATYP than HC. (C) Estimated hip strength as assessed by mean section modulus was lower in men with AN compared to HC. (D) Mean section modulus Z-scores at the narrow neck and femoral shaft were lower in AN than HC. (E) The prevalence of any section modulus Z-score <−1 was higher in AN, while the prevalence of any section modulus Z-score <−2 was higher in AN and ARFID, than HC. (F) Mean buckling ratio, with a higher buckling ratio denoting more impaired estimated hip strength, was higher in AN than HC at the narrow neck. Mean ± SEM. *P ≤ 0.05

FIGURE 2

Positive linear relationship between BMI and (A) postero-anterior (PA) spine, (B) total hip and (C) femoral neck bone mineral density (BMD) Z-scores, as well as appendicular lean mass and (D) PA spine, (E) total hip and (F) femoral neck BMD Z-scores, in men with anorexia nervosa, avoidant/ restrictive food intake disorder, atypical anorexia nervosa and healthy controls

FIGURE 3

Men with eating disorders and vitamin D deficiency (25OH vitamin D level <20 ng/mL) had lower mean (A) bone mineral density (BMD) Z-scores and (B) section modulus at all sites, as well as (C) higher narrow neck buckling ratio compared to those with 25OH vitamin D sufficiency. Mean ± SEM. *P ≤ 0.05