Abstract and Introduction
Objective: Low bone mineral density (BMD) is a frequent and invalidating consequence of chronic undernourishment in patients with anorexia nervosa (AN). The aim of this study was to assess prevalence and clinic-biological correlates of low BMD and fractures in extremely undernourished inpatients with AN.
Design: Retrospective cohort study.
Patients and Measurements: This study included 97 extremely malnourished female inpatients with AN consecutively admitted over 2 years. Clinical-biological variables, history of fractures and BMD by dual-energy X-ray absorptiometry (DXA) were examined to find predictors of low BMD and fractures.
Results: The prevalence of low BMD was of 51% for lumbar spine and 38% for femoral neck. Z-scores were lower at lumbar spine (−2.2 ± 1.2 SD) than at femoral neck (−1.9 ± 0.9 SD) (P<.01). Fragility fractures were reported by 10% of patients. BMD was mainly predicted by FFM, illness duration, age at onset and restricting AN (P<.05). Fractures were predicted by sodium concentrations, femoral neck Z-score and illness duration (P<.03).
Conclusion: Extremely severe patients with AN have high prevalence of low BMD, predicted by severity and chronicity of malnutrition.
Anorexia nervosa (AN) is a severe eating disorder characterized by an emotional and cognitive inability to maintain a normal weight. Quantitative and qualitative restriction of nutritional intakes, purging behaviours, physical hyperactivity and laxative abuse are the main strategies to control weight and shape. These behaviours are maintained by a persisting distortion of body image, generating a vicious circle of weight loss. Prevalence varies between 0.9% and 4% among women and is 10 to 13 times lower among men.[2–4]
Weight control strategies progressively lead to malnutrition, which in turn can generate acute and chronic somatic complications, functional damage and decreased quality of life. Bone mineral density (BMD) loss is a potentially irreversible consequence of AN,[6,7] favoured by the combined effect on malnutrition, vitamin D deficiency, hypoestrogenism, elevated serum cortisol and low body mass index (BMI).[7,8] Epidemiological studies indicate that 45 to 95% of patients with AN suffer from osteopenia and up to 40% suffer from osteoporosis.[9–11] Bone fragility exposes these patients to a sevenfold increased risk of fractures, compared to healthy individuals of the same age and gender. The prevalence of fractures is estimated at 31% in adolescents with AN, 12% higher than healthy controls at normal weight. The occurrence of alterations of bone structure even at mild BMD decreases is not excluded in AN.
A recent study on 336 adult patients with AN found a prevalence of low BMD of 20%. Identified factors of low BMD are duration of illness and of amenorrhea, age, precocity of AN onset, restricting type, low body mass index (BMI), hyponatremia, increased cortisol levels,[12,14] and lean and fat mass percentage.[15,16]
In the current study, we aimed to replicate an inquiry of bone mineral status in AN in a population at extreme stages of malnutrition (average BMI<13 kg/m2). The primary aim of this research was to determine the prevalence and severity of low BMD and fractures. The secondary aim was to explore which clinic-biological variables were the best predictors of BMD loss and fractures.
Clin Endocrinol. 2021;95(3):423-429. © 2021 Blackwell Publishing