in a case control study derived from Swedish national health care registry data.
Atopic dermatitis (AD) is known to be associated with other atopic conditions, and there is increasing evidence it is associated with some nonatopic conditions, including some cancers, cardiovascular disease, and neuropsychiatric disorders, according to Lina U. Ivert, MD, of the dermatology and venereology unit at the Karolinska Institutet, Stockholm, and coauthors. There are also some data indicating that autoimmune diseases, particularly those involving the skin and gastrointestinal tract, are more common in people with AD.
The aim of their study, published in the British Journal of Dermatology, was to investigate a wide spectrum of autoimmune diseases for associations with AD in a large-scale, population-based study using Swedish registers. Findings could lead to better monitoring of comorbidities and deeper understanding of disease burden and AD pathophysiology, they noted.
Large-scale study
With data from the Swedish Board of Health and Welfare’s National Patient Register on inpatient diagnoses since 1964 and specialist outpatient visits since 2001, the investigators included all patients aged 15 years and older with AD diagnoses (104,832) and matched them with controls from the general population (1,022,435). The authors noted that the large number of people included in the analysis allowed for robust estimates, and underscored that 80% of the AD patients included had received their diagnosis in a dermatology department, which reduces the risk of misclassification.
Association with autoimmune disease
The investigators found an association between AD and autoimmune disease, with an adjusted odds ratio) of 1.97 (95% confidence interval, 1.93-2.01). The association was present with several organ systems, particularly the skin and gastrointestinal tract, and with connective tissue diseases. The strongest associations with autoimmune skin diseases were found for dermatitis herpetiformis (aOR, 9.76; 95% CI, 8.10-11.8), alopecia areata (aOR, 5.11; 95% CI, 4.75-5.49), and chronic urticaria (aOR, 4.82; 95% CI, 4.48-5.19).
AD was associated with gastrointestinal diseases, including celiac disease (aOR, 1.96; 95% CI, 1.84-2.09), Crohn disease (aOR 1.83; CI, 1.71-1.96), and ulcerative colitis (aOR 1.58; 95% CI, 1.49-1.68).
Connective tissue diseases significantly associated with AD included systemic lupus erythematosus (aOR, 1.65; 95% CI, 1.42-1.90), ankylosing spondylitis (aOR, 1.46; 95% CI, 1.29-1.66), and RA (aOR, 1.44; 95% CI,1.34-1.54]). Hematologic or hepatic autoimmune disease associations with AD were not observed.
Stronger association with multiple diseases
The association between AD and two or more autoimmune diseases was significantly stronger than the association between AD and having one autoimmune disease. For example, the OR for AD among people with three to five autoimmune diseases was 3.33 (95% CI, 2.86-3.87), and was stronger in men (OR, 3.96; 95% CI, 2.92-5.37) than in women (OR, 3.14; 95% CI, 2.63-3.74).
Sex differences
In the study overall, the association with AD and autoimmune diseases was stronger in men (aOR, 2.18; 95% CI, 2.10-2.25), compared with women (aOR, 1.89; 95% CI, 1.85-1.93), but this “sex difference was only statistically significant between AD and RA and between AD and Celiac disease,” they noted.
Associations between AD and dermatomyositis, systemic scleroderma, systemic lupus erythematosus, Hashimoto’s disease, Graves disease, multiple sclerosis, and polymyalgia rheumatica were found only in women. Dr. Ivert and coauthors observed that “women are in general more likely to develop autoimmune diseases, and 80% of patients with autoimmune diseases are women.”
Provocative questions
Commenting on the findings, Jonathan Silverberg, MD, PhD, MPH, associate professor of dermatology, George Washington University, Washington, said, “At a high level, it is important for clinicians to recognize that atopic dermatitis is a systemic immune-mediated disease. AD is associated with higher rates of comorbid autoimmune disease, similar to psoriasis and other chronic inflammatory skin diseases.”
“At this point, there is nothing immediately actionable about these results,” noted Dr. Silverberg, who was not an author of this study. “That said, in my mind, they raise some provocative questions: What is the difference between AD in adults who do versus those who do not get comorbid autoimmune disease? Does AD then present differently? Does it respond to the same therapies? These will have to be the subject of future research.”
The study was funded by the Swedish Asthma and Allergy Association Research Foundation, Hudfonden (the Welander-Finsen Foundation), and the Swedish Society for Dermatology and Venereology. The authors disclosed no conflicts of interest.
SOURCE: Ivert LU et al. Br J Dermatol. 2020 Oct 22. doi: 10.1111/bjd.19624.