Background: Atopic dermatitis (AD) has been proposed as systemic disease due to underlying systemic inflammation and reports on various comorbidities.
Objective: This study aimed to examine the associations between AD and (non-atopic) multimorbidity in a population-based cohort from the Northern Netherlands and to identify differences in multimorbidity patterns between multimorbid participants with and without AD.
Methods: We assessed lifetime prevalence of 52 diseases, from 15 domains, combining data from questionnaires, medication records and clinical assessments within the Lifelines Cohort. Lifetime AD was self-reported, physician-diagnosed and disease severity based on the Patient Oriented Eczema Measure. Multimorbidity was defined as lifetime presence of at least two diseases, while non-atopic multimorbidity excluded asthma, rhinitis and food allergy. A composite morbidity score (cMS) indicated the degree of multimorbidity. We analysed associations of AD and AD severity with multimorbidity and cMS using binary and multinomial logistic regression, adjusting for age and sex and additionally adjusting for socioeconomic and lifestyle factors. Patterns of non-atopic multimorbidity based on disease domains were explored using Latent Class Analysis (LCA), stratified by AD presence.
Results: Among 37,193 participants, 8.7% had AD. The risk for non-atopic multimorbidity was 1.47-fold higher in participants with AD, particularly for those with moderate-to-severe disease (adjusted Odds Ratio (aOR) 1.74 vs. mild AD aOR 1.41). The association strengthened with higher degrees of non-atopic multimorbidity, reaching 2.09-fold for ≥5 diseases. When considering atopic diseases in the definition of multimorbidity and the cMS, the associations with AD were even stronger. Further adjustments for socioeconomic and lifestyle factors were corroborative. We identified five distinct multimorbidity classes, among participants with and without AD, with two differing across the groups. One class, characterized by the orofacial domain was only present among those with AD, while another class, resemblant of the metabolic syndrome showed more respiratory contribution in AD with further differences regarding cardiometabolic involvement.
Conclusion: Participants with AD, especially moderate-to-severe cases, are at higher risk for (non-atopic) multimorbidity and showed unique patterns of non-atopic multimorbidity with regards to orofacial and cardiometabolic diseases. Whether this is due to systemic inflammation in AD, needs further investigation.
Key words: atopic dermatitis, multimorbidity, comorbidities, pattern analysis