Atopic dermatitis and the risk of eating disorders: A population-based cohort study
Authors: Saana Kauppi, Jari Jokelainen, Markku Timonen, Kaisa Tasanen, Laura Huilaja
Journal: Journal of the American Academy of Dermatology (2021)

To the Editor: Atopic dermatitis (AD) is a common chronic inflammatory skin disease that significantly impairs the quality of life of patients and their relatives1Langan S.M. Irvine A.D. Weidinger S. Atopic dermatitis.Lancet. 2020; 396: 345-360Abstract Full Text Full Text PDF PubMed Scopus (387) Google Scholar and is associated with mental disorders at any age.2Kauppi S. Jokelainen J. Timonen M. Tasanen K. Huilaja L. Adult patients with atopic eczema have a high burden of psychiatric disease: a Finnish nationwide registry study.Acta Derm Venereol. 2019; 99: 647-651Crossref PubMed Scopus (15) Google Scholar,3Xie Q.W. Dai X. Tang X. Chan C.H. Chan C.L. Risk of mental disorders in children and adolescents with atopic dermatitis: a systematic review and meta-analysis.Front Psychol. 2019; 10: 1-12PubMed Google Scholar Despite emerging knowledge of other comorbidities, no data on eating disorders (EDs) in patients with AD exist. We conducted this retrospective, nationwide, registry-based study to determine whether the risk of EDs is higher in AD patients than in the general population. The Finnish Care Register for Health Care database was queried to extract all AD-diagnosed individuals between 1987 and 2018. Only patients under the age of 18 years at the time of the first AD diagnosis were included in the study population. A group of age- and sex-matched control individuals was derived from the Finnish Population Register Center database (Supplementary Methods, available via Mendeley at https://data.mendeley.com/datasets/gjh23tttfw/1.) The prevalence of preselected codes for EDs (Supplementary Table I, available via Mendeley at https://data.mendeley.com/datasets/gjh23tttfw/1) for both the cases and controls was analyzed, and their associations were evaluated using a logistic regression model. A total of 70,584 individuals with a diagnosis of AD and 270,783 controls were included in the present study (Table I). In an adjusted model controlling for birth year, sex, depression, anxiety, and food allergy, the AD patients had higher odds of having any ED than the controls at the age of both 18 and 30 years. The highest association between AD and ED was found in relation to bulimia nervosa (adjusted odds ratio 2.31; 95% CI 1.54-3.48), followed by binge eating disorder (adjusted odds ratio 1.86; 95% CI 1.29-2.68) at the age of 18 years (Table II). It is of note that a high prevalence of food allergies in the AD population did not seem to explain the co-occurrence of AD and ED.Table ICharacteristics of the study populations with and without atopic dermatitisAtopic dermatitisControlsN70,584∗Excluding 499 individuals from the final study population with the diagnosis of atopic dermatitis recorded only once in the Finnish Care Register for Health Care.270,783†Excluding 299,217 individuals either with no records or with a recorded diagnosis of AD in the Finnish Care Register for Health Care.Female45.3%48.3%Male54.7%51.7%Age at the onset of ED‡Data were represented as years, mean (standard deviation).16.4 (4.19)16.1 (3.62)Prevalence of food allergy21,892 (31.0%)3870 (1.43%)Prevalence of ED by the age of 18 y424 (0.6%)938 (0.35%)Prevalence of ED by the age of 30 y542 (0.77%)1275 (0.47%)ED, Eating disorder.∗ Excluding 499 individuals from the final study population with the diagnosis of atopic dermatitis recorded only once in the Finnish Care Register for Health Care.† Excluding 299,217 individuals either with no records or with a recorded diagnosis of AD in the Finnish Care Register for Health Care.‡ Data were represented as years, mean (standard deviation). Open table in a new tab Table IIOdds ratios of eating disorder diagnoses in study populations with and without atopic dermatitisComorbidityBy the age of 18yBy the age of 30 yGroupN (%)Crude OR (95% CI)Adjusted OR (95% CI)∗Adjusted for age, sex, depression, anxiety and food allergy.N (%)Crude OR (95% CI)Adjusted OR (95% CI)∗Adjusted for age, sex, depression, anxiety and food allergy.All eating disordersAD424 (0.6)1.74 (1.55-1.95)1.31 (1.15-1.49)542 (0.77)1.64 (1.48-1.81)1.25 (1.11-1.40)Controls938 (0.35)ReferenceReference1,275 (0.47)ReferenceReferenceAnorexia nervosaAD214 (0.3)1.54 (1.31-1.80)1.15 (0.96-1.38)266 (0.38)1.47 (1.28–1.70)1.09 (0.93-1.28)Controls534 (0.2)ReferenceReference693 (0.26)ReferenceReferenceBulimiaAD45 (0.06)2.79 (1.90-4.09)2.31 (1.54-3.48)90 (0.13)1.75 (1.37-2.25)1.58 (1.21-2.06)Controls62 (0.02)ReferenceReference197 (0.07)ReferenceReferenceBinge eating disorderAD57 (0.08)2.33 (1.68-3.24)1.86 (1.29-2.68)82 (0.12)2.25 (1.71-2.95)1.68 (1.25-2.27)Controls94 (0.03)ReferenceReference140 (0.05)ReferenceReferenceEDNOSAD273 (0.39)1.91 (1.65–2.21)1.39 (1.17-1.63)367 (0.52)1.84 (1.62-2.08)1.33 (1.16-1.53)Controls549 (0.2)ReferenceReference769 (0.28)ReferenceReferenceAD, Atopic dermatitis; EDNOS, eating disorder not otherwise specified; OR, odds ratio.∗ Adjusted for age, sex, depression, anxiety and food allergy. Open table in a new tab ED, Eating disorder. AD, Atopic dermatitis; EDNOS, eating disorder not otherwise specified; OR, odds ratio. In the present study, we found a positive association between AD and ED. A negative cutaneous body image may be the link between AD and mental disorders4Butler M.J. Perrini A.A. Eckel L.A. The role of the gut microbiome, immunity, and neuroinflammation in the pathophysiology of eating disorders.Nutrients. 2021; 13: 500Crossref PubMed Scopus (11) Google Scholar because both AD and ED have been shown to be associated with a disturbed body image, and negative attitudes toward weight, body, and eating are important factors influencing the onset and maintenance of EDs.5Hinkley S.B. Holub S.C. Menter A. The validity of cutaneous body image as a construct and as a mediator of the relationship between cutaneous disease and mental health.Dermatol Ther (Heidelb). 2020; 10: 203-211Crossref PubMed Scopus (7) Google Scholar In addition, autoreactivity, defined as evidence of an immune response against self-antigens, may also play a role in the pathophysiology behind the association between AD and ED because immune dysregulation has been shown to be linked to both the disease entities.1Langan S.M. Irvine A.D. Weidinger S. Atopic dermatitis.Lancet. 2020; 396: 345-360Abstract Full Text Full Text PDF PubMed Scopus (387) Google Scholar,4Butler M.J. Perrini A.A. Eckel L.A. The role of the gut microbiome, immunity, and neuroinflammation in the pathophysiology of eating disorders.Nutrients. 2021; 13: 500Crossref PubMed Scopus (11) Google Scholar The main strength of our study is the high validity and completeness of the medical register data. We admit that our results need to be interpreted with caution because in large datasets, statistical significance may be seen with minor differences that are not clinically relevant. Additionally, we could not consider all confounding factors—eg, socioeconomic status—although E values suggested that unmeasured confounding is unlikely to explain the association (Supplementary Table I). Our findings suggest that AD patients are at particular risk of concomitant ED. Hence, it is important to be aware of the cutaneous signs of hidden ED as well as discuss eating habits and possible anxiety related to food in patients with AD. Dr Kauppi has received educational grants from Novartis, LEO Pharma, Sanofi Genzyme, AbbVie, and Janssen-Cilag and honoraria from Sanofi Genzyme for speaking. Dr Tasanen has received educational grants from Novartis and Pfizer and honoraria from Novartis, AbbVie, Janssen-Cilag, Sanofi Genzyme, and Lilly for consulting and/or speaking. Dr Huilaja has received educational grants from Takeda, Janssen-Cilag, Novartis, AbbVie, and LEO Pharma; received honoraria from Sanofi Genzyme, Novartis, AbbVie, and UCB Pharma for consulting and/or speaking; and is an investigator for AbbVie. Dr Timonen and Author Jokelainen have no conflicts of interest to declare.