Body mass index and in-hospital mortality in anorexia nervosa: data from the Japanese Diagnosis Procedure Combination database.

One of the main purposes of admission for anorexia nervosa is to manage acute medical conditions related to this condition. Factors associated with in-hospital mortality in anorexia nervosa remain unclear. This study describes the clinical features of anorexia nervosa patients requiring hospitalization in Japan. We analyzed the association between in-hospital mortality and body mass index upon admission using a currently available, nationwide hospital-based database. We identified 669 eligible patients with anorexia nervosa (BMI ≤ 16.5) from 229 hospitals between July and December, 2010. More than 90 % of the patients were female and 100 patients were admitted involuntarily. The average body mass index was 13.1, and the in-hospital mortality rate was 0.7 %. Five patients who died had a BMI under 11, indicating that patients with an extremely low BMI may be likely to die, despite admission.