Eczema affects 20% of children and up to 10% of adults in developed countries. Eczema is a challenging disease causing significant problems for sufferers and their families. The severity of eczema can vary substantially between people and within the same person over time. There is paradigm shift towards understanding eczema as a systemic inflammatory disorder with a dysregulated immunity. This has resulted from multiple studies, where an association with multiple comorbidities has been found. Eczema is associated with changes in the immune system, including inflammation and an increased risk of infection. Eczema may also be associated with low numbers of a particular type of white blood cell (lymphocyte count), either due to the use of drugs that suppress the immune system to treat severe eczema, or due to movement of white blood cells (lymphocytes) to the skin. This low white blood cell count may explain the increased risk of infection. This study will determine if there is an association between eczema and infections, and if infection risk is explained by a low lymphocyte count.
We aim to use data from the Clinical Practice Research Database (CPRD) and Hospital Episodes Statistics (HES) to examine associations between eczema and infections, and the role of lymphopenia. We will identify people with eczema in CPRD using a validated algorithm comprising Read codes and therapies and/or using ICD-10 codes in linked HES data.
Increased infection prevalence has been associated with eczema. There is a lack of longitudinal population-based data to support these associations. We will undertake a matched-cohort study to assess the strength of association between eczema and infections (Phase 1). We will then assess if this association is mediated or modified by lymphopenia (Phase 2). We will use conditional Poisson or negative binomial regression models to compute rate ratios with 95% confidence intervals to assess the associations between eczema and different infections. We will examine how robust our results are using several sensitivity analyses.
Health Outcomes to be Measured:
Rate or specific cutaneous and non-cutaneous infections in people with and without eczema
• Hospitalisations for infections in people with and without eczema
• Rate of specific cutaneous and non-cutaneous infections, and hospitalisations for infections in people with and without eczema stratified by lymphopenia status
HES Admitted Patient Care;Patient Level Index of Multiple Deprivation;Practice Level Index of Multiple Deprivation