A Growing Trend: Lower Admission Weights for Patients with AN

According to British eating disorders specialists Drs. Richard Sly and Bryony Bamford, inpatient eating disorders unit are increasingly being asked to admit patients at lower body mass indexes (BMIs), often delaying hospital treatment until it is medically unavoidable. At their hospital, St. George’s Hospital, London, there has been a consistent drop in inpatient BMIs for adults with anorexia nervosa (AN), from a yearly average of 14.1 kg/m² in 2007 to 13.6 kg/m² in 2009.

The two physicians designed a study to explore two hypotheses: first, that patients admitted at lower BMIs will have poorer weight outcomes at the end of treatment, and next, that these patients will have higher rates of re-admission within one year of discharge (Eur Eat Disorders Rev 2011; 19:407). To test the hypotheses, the authors studied 79 females and 3 males recruited from a national eating disorder inpatient unit. The mean age of participants was 27 years and participants met DSM-IV criteria for AN restrictive subtype (80.5%) or AN binge-purge subtype (19.5%). Participants were assigned to two groups: those with a BMI greater than 15 (15 patients) or BMIs less than 15 kg (67 patients). Patients were allocated to a “poor weight outcome” subgroup if their discharge weight was less than 17.5 or to “good weight outcome” subgroup if their discharge weight was more than 17.5.

How patients did

As the authors had anticipated, there was a significant positive correlation between a patient’s admission BMI and discharge BMI. Patients who had been admitted with BMIs greater than 15 had significantly higher BMIs on discharge than did those whose BMIs had been less than 15 on admission. Dropout rates were similar between the two groups ( 53% and 54%). Weight gained and duration of treatment were approximately the same in the two groups of patients.

As predicted, 95.5% of patients who had been originally admitted for treatment at BMIs less than 15 were readmitted to treatment within a year of discharge; only 1 patient with a pre-admission BMI above 15 was re-admitted. Thus, there was a significant relationship between low admission BMI and subsequent re-admission for treatment.

As Drs. Sly and Bamford note, no differences were seen in total weight gain across hospital stay, which meant that those patients admitted at lower weight were subsequently being discharged at lower weights. Nearly one-third of patients admitted below a BMI of 15 were readmitted for treatment within 1 year. Should longer hospital stays be promoted to achieve healthy weight gain before discharge or should patients be admitted at an earlier stage of AN to maximize the chances of patients achieving a healthy weight gain before being discharged? The authors obviously vote for being proactive, and admitting patients earlier to achieve a better outcome and reduce the need for re-hospitalization.