Cohort studies on 71 outcomes among people with atopic eczema in UK primary care data

Atopic eczema may be related to multiple subsequent adverse health outcomes. Here, we provide evidence to judge and compare associations between eczema and a comprehensive set of outcomes. We conducted 71 cohort studies (age, sex, general practice-matched) using Clinical Practice Research Datalink Aurum primary care records (1997-2023), comparing up to 3.6 million people with eczema to 16.8 million without. Eczema was associated with subsequent diagnosis of outcomes with adjusted hazard ratios (99% confidence intervals) from Cox regression of up to 4.02(3.95-4.10) for food allergy (rate difference [RD] per 1,000 person-years of 1.5). Besides strong associations with atopic and allergic conditions (e.g., asthma 1.87[1.39-1.82], RD5.4) and skin infections (e.g., molluscum contagiosum 1.81[1.64-1.96], RD1.8), the strongest associations were with Hodgkin's lymphoma (1.85[1.66-2.06], RD0.02), Alopecia Areata (1.77[1.71-1.83], RD0.2), Crohn's disease (1.62[1.54-1.69], RD0.1), Urticaria (1.58[1.57-1.60], RD1.9), Coeliac disease (1.42[1.37-1.47], RD0.1), Ulcerative colitis (1.40[1.34-1.46], RD0.1), Autoimmune liver disease (1.32[1.21-1.43], RD0.01), and Irritable bowel syndrome (1.31[1.29-1.32], RD0.7). Sensitivity analyses revealed the impact of consultation bias or choice of cohort age cut-off on findings. Comparatively large HRs in severe eczema were seen for some liver, gastrointestinal and cardiovascular conditions, osteoporosis, and fractures. Most cancers and neurological conditions were not associated with eczema.