Predictors of Outcome in Inpatients with Anorexia Nervosa: A Prospective Multi-Center Study
Authors: Denise Kästner, Antje Gumz, Bernhard Osen, Ulrich Voderholzer, Eileen Wollburg, Matislava Karacic, Björn Meyer, Matthias Rose, Bernd Löwe
Journal: Psychotherapy and Psychosomatics (2015)

Inpatient treatments for anorexia nervosa (AN) are highly effective with respect to rapid weight gain. Nevertheless, the proportion of patients with poor responses in recent naturalistic studies appears to be critically high: more than half of the patients remain underweight (BMI <17.5) at discharge [1,2], and there is a strong need for more effective treatments for inpatients with AN [3].An important starting point for evidence-based improvements and tailored recommendations is knowledge of the factors associated with poor responses. However, only one study predicted adult inpatient BMI gain using a comprehensive set of potential predictors [4]. This study found that BMI gain depended solely on the therapy duration. Thus, the predictive value of the remaining variables was judged to be insufficient, and the need for future research was highlighted. Other studies focused on the influence of one specific factor on BMI gain, potentially ignoring yet unidentified but important control variables. Consequently, we aimed to analyze predictors of BMI gain in a large sample of adult inpatients with AN.We conducted a prospective multi-center study with a pre-post design. Three participating hospitals offering adult eating disorder (ED) specialist treatment (Schön clinics Bad Bramstedt, Prien, and Hamburg-Eilbek) recruited patients who met the following inclusion criteria: primary DSM-IV diagnosis of AN; female gender; a minimum age of 16 years, and sufficient German language skills. The exclusion criteria were acute drug or alcohol abuse, acute suicidality, psychotic or bipolar disorders, or severe somatic disorders. Written informed consent was obtained prior to study inclusion. The local research ethics committees (the Medical Associations of Hamburg and Schleswig-Holstein and the University Medical Centre of Munich) approved the study.At admission (t0) and discharge (t1), the participants completed a battery of standardized questionnaires (ED pathology: EDI-2 [5]; depressive symptoms: PHQ-9; anxiety symptoms: GAD-7; somatic symptoms: PHQ-15 [6], and therapy motivation: FEVER [7]). Patient weight was measured at t0 and t1 and weekly during treatment by a staff member. Patients with missing data for all BMI measurements after t0 or missing t0 BMI were excluded from the analysis. We tested for baseline differences between the therapy completers and noncompleters using two-tailed t tests and χ2 tests. For t0 and t1 BMIs, paired sample t tests and effect sizes (Cohen's d) were conducted. Inpatient BMI gain was predicted using stepwise linear regression analysis with the following predictors: therapy duration; median split age; age of onset; living alone; partnership; education; previous hospitalizations; AN subtype; BMIt0; centers; PHQ-9t0; PHQ-15t0; GAD-7t0; median split FEVERt0, and all EDI-2t0 subscales. All analyses were calculated for the therapy completers and the intention-to-treat (ITT) sample.We recruited 233 patients (April 2010-July 2012). Twenty-five patients were removed from the analysis because of implausible or missing BMI measurements. In 3 cases, BMIt1 was imputed using the last observation carried forward (the BMI 1 week earlier). Of the 208 patients analyzed, 176 completed the therapy (noncompletion rate: 15.4%). The regression analyses included the patients who had complete data for all predictor variables.The ITT study sample consisted of patients with a mean age of 26.9 years (SD = 8.6, range: 17-58) and an average age of illness onset of 17.8 years (SD = 5.9). The majority had a restrictive AN subtype (n = 103, 53.7 %) and at least one previous psychiatric or psychosomatic inpatient stay (n = 120, 57.7 %). Only about one third of the patients (n = 67, 32.2 %) were currently in a partnership. Therapy completers stayed longer in the hospital compared to noncompleters (t = 7.01, p < 0.001, meanCompleters = 11.8 weeks, SDCompleters = 5.2; meanNoncompleters = 5.1, SDNoncompleters = 3.1). We found no baseline differences between therapy completers and therapy noncompleters with respect to clinical or demographic variables. As expected, the BMI significantly improved from t0 to t1 with an effect size of 1.16 within the ITT sample (t = -19.7, p < 0.001; meant0 = 15.0, SDt0 = 1.6, ranget0: 10.8-18.0; meant1 = 16.9, SDt1 = 1.7, ranget1 = 11.8-20.7) and an effect size of 1.35 for completers (t = -20.1, p < 0.001; meant0 = 15.0, SDt0 = 1.6, ranget0 = 10.8-18.0; meant1 = 17.1, SDt1 = 1.5, ranget1 = 12.8-20.7).The strongest predictor of BMI gain was the therapy duration (fig. 1). Moreover, a lower t0 BMI, primary education (vs. university degree), lower ineffectiveness, and, within the ITT sample, an older age of onset emerged as significant predictors of BMI gain (table 1).Our analysis of the factors influencing adult inpatient BMI gain identified previously unknown factors and explained a considerably higher amount of variance compared with the only previous related study (60 vs. 41%) [4]. Consistent with earlier results, we found the treatment duration to be the strongest predictor [1,4]. This result is not surprising considering the use of therapeutic weight contracts; however, it is important for ongoing discussions of reducing treatment durations. The clinically most relevant finding appears to be the influence of the EDI-2 ineffectiveness subscale, which is conceptually very similar to low self-esteem [5]. The result is in line with previously reported associations between self-esteem and outcome [8]. Furthermore, low self-esteem has been conceptualized as a decisive maintaining factor within the 'transdiagnostic' theory of EDs [9]. Within the ITT analysis, patients who were younger at the onset of AN were identified as a risk group. Thus, early interventions targeting a young age group might be important [10]. Consistent with the work by Schlegl et al. [1], patients with a higher level of education were found to be more vulnerable. Future research should address the role of academic achievement as maintaining factor. Finally, the significance of BMI at t0 most likely reflects the mechanism of a regression to the mean [1].In summary, the present model explained a major amount of variance in adult inpatient BMI gain by using a large sample size, a multi-center design, and a comprehensive list of predictors. However, we were unable to consider all variables with a potential influence and cannot draw conclusions about the development after t1. Future studies might consider including additional predictors such as the duration of untreated illness or the confidence in the ability to change [2] as well as follow-up measurements. The robust finding of a strongly positive effect of longer treatment durations on short-term BMI gain in adult inpatients with AN seems highly relevant to health policy. From a clinical perspective, therapeutic work on self-esteem may be a starting point for improving treatments.This study was funded by a research grant from the Swiss Anorexia Nervosa Foundation to Prof. Dr. B. Löwe and Dr. B. Meyer.We gratefully acknowledge the support of all physicians and psychotherapists at the three study centers who contributed to this study. We thank all patients for their participation in our study.The authors declare that they have no conflicts of interest.D.K. and A.G. contributed equally to this work.