Our study results show that women with AN reported significantly impaired function compared to healthy, normal-weight controls on all aspects measured, i.e. disease-specific HRQoL (EDQLS), generic health status (SF-36), eating disorder psychopathology (EDI-3), psychological well-being (WHO-5), work functioning (WSAS), and depressive symptomatology (BDI). In addition, poorer HRQoL (lower EDQLS score) in AN were predicted by more severe eating disorder symptoms (higher EDI-3 score), more symptoms of depression (higher BDI score), poorer psychological health (lower scores for SF-36 emotional role and vitality), and older age.
Comorbid mental disorders are common in AN and can require more intensive management of AN [29] as well as contribute to poorer outcome in terms of weight gain [30]. Our study participants were not asked about diagnosed comorbidities, and the high use of medication in the AN group indicated high psychiatric comorbidity. Among women with AN, 31% (n = 65) reported daily use of medication, with antidepressants representing almost half of this (n = 30). Ten of these were taking daily antipsychotic medication, while the remaining 25 women took daily medication for a somatic disorder (e.g. diabetes, thyroid disorder). Study participants with AN reported a significantly higher level of depressive symptoms compared to controls, with median scores indicating severe depression. A recently published scoping review found that comorbid depression was a negative predictor of prognosis in AN [29].
The current study confirms the significantly impaired HRQoL measured by SF-36 and EDQLS in women with AN, as reported previously [2, 6]. Our finding that severe psychopathology in terms of eating disorders symptoms and depression predicted poorer disease-specific HRQoL is in line with AN studies assessing generic HRQoL with SF-36 [31] and EQ-VAS [14]. Several identical subscales of the EDI-3 were associated with poorer HRQoL in both women with AN and controls, but it appeared that impaired HRQoL in AN was also associated with low self-esteem and fear of reaching adulthood. We also found that poorer specific HRQoL was associated with low levels of vitality (SF-36 VT score) and limitations in everyday life due to emotional problems (SF-36 RE score). These may be important aspects of AN to consider during treatment as they are likely to contribute to low motivation for completion of treatment. Jones et al. [32] suggested that motivation may be important for treatment completion, with completers being more motivated to improve their symptoms and their general quality of life.
Finally, we found that higher age predicted more impaired HRQoL in women with AN. In the general population, SF-36 scores for physical health decreased with age while SF-36 scores for mental health showed no clear age pattern [33]. Age has not previously been identified as a predictor for disease-specific HRQoL in AN [13], although higher age has been associated with poorer clinical outcome in AN [34, 35]. In population-based studies, aging itself has been perceived to decrease QoL, but this effect tends to diminish when controlled for other factors [36].
It is interesting that eating disorder pathology measured by EDI-3 was associated with HRQoL in both women with AN and controls. The EDI-3 measures psychological constructs that are clinically relevant in individuals with eating disorders, and the controls were not expected to exhibit eating disorder behavior. Eating disorders are likely to be present as a continuum, however, and include milder forms of disordered eating that would be present in a general population—and particularly in a young, female control group as in the current study. In future studies it would be interesting to investigate differences in HRQoL between patients with an ED, people with elevated ED symptoms but not a diagnosis, and people with non-disordered eating. The validity and reliability of applying the EDI-3 to healthy people has been questioned [37, 38] as it has been designed specifically for individuals with eating disorders. When we used regression analysis to further investigate the predictive value of the EDI-3 subscales, we found similar results for women with AN and controls in terms of Drive for thinness, Personal alienation, Interpersonal insecurities, and Emotional dysregulation. However, Low self-esteem and Maturity fears were additionally associated with poorer HRQoL only in women with AN. Self-esteem issues and fear of adulthood/maturing are both inherent features of people with AN and appear to play a significant role in determining self-reported HRQoL. While low individual body weight, i.e. as characterized in drive for thinness, may be a means of coping with the psychological conflict and imbalance of an eating disorder, the psychopathology in terms of emotional dysregulation and personal alienation may be consequences of the disorder. However, these factors may also very well be present in young females not diagnosed with an eating disorder but simply going through the tumultuous time of adolescence/early adulthood. When these different factors occur together, they appear to be related to a particularly low quality of life.
As expected, women with AN had a significantly lower median BMI compared to healthy controls, as well as a lower BMI-for-age percentile. However, about 40% of the 13–17-year-olds with AN had a BMI-for-age percentile in the normal range despite being diagnosed with AN and in treatment at specialized centres for the AN. The participants in our study thus comprised patients at very different stages of AN. We found that BMI (including BMI-for-age) did not predict HRQoL in any of the regression models. This is in line with Abbate-Daga et al. [31], who found that eating disorder symptomatology but not BMI had an impact on HRQoL. It is in contrast, however, to the findings of Bamford et al. [12], who reported that changes in BMI predicted improvement in HRQoL. The latter study comprised a different and smaller selection of AN individuals than our study as it included 63 adults with severe and enduring AN. This might explain the difference in results as patients with severe and enduring AN would be expected to have a higher burden of eating disorder symptomatology and to be more physically affected by their emaciated state, thus lowering their HRQoL. The abovementioned findings contribute to the argument that BMI cannot stand alone in determining outcome, but it is important to include PRO measures. It could be used in monitoring treatment response. In previous studies nadir BMI has been determined to be a strong predictor of mortality/poor outcome in AN [39], but in this study BMI was not associated with HRQoL, which needs to be considered when assessing outcome.
The strengths of our study are that it represents the largest AN cohort study to date, includes a wide range of assessment measures, and collects data from treatment-seeking individuals in all regions of Denmark. The analyses are further strengthened by the absence of missing values on the assessment measures. A limitation of the current study is that the controls were significantly older than the women with AN (median 24 years vs. 22 years). Recruitment of controls was achieved by advertising online through social media, and the results reflect self-selection. Thus, the control group is perhaps best described as normal-weight women who did not take regular medication.
The results of this study would be useful as reference material for intervention studies where EDQLS is included as an effect parameter. We further hope that the study results will help to stimulate interest in patient-reported outcome measures in AN, which presents very special challenges in the form of patient egosyntonicity and ambivalence. Biomedical effect measures cannot stand alone in AN as ‘successful’ treatment in terms of anthropometric and biomedical effect parameters can also be associated with reduced patient-reported quality of life.