The risk of venous thromboembolism in atopic dermatitis: a matched cohort analysis in UK primary care.

Background: Atopic dermatitis (AD) is a common chronic inflammatory skin condition. While other chronic inflammatory conditions are associated with increased risk of venous thromboembolism (VTE), associations between AD and VTE have not been established.

Objectives: We examined whether AD is associated with an increased risk of VTE in a population-based study.

Methods: Electronic health records were extracted from UK general practices contributing to the Optimum Patient Care Research Database (1 January 2010 to 1 January 2020). All adults with AD were identified (n = 150 975) and age- and sex-matched with unaffected controls (n = 603 770). The risk of VTE, consisting of pulmonary embolism (PE) or deep-vein thrombosis (DVT), was compared in people with AD vs. controls using Cox proportional hazard models. PE and DVT were examined separately as secondary outcomes.

Results: We identified 150 975 adults with active AD and matched them with 603 770 unaffected controls. During the study, 2576 of those with active AD and 7563 of the matched controls developed VTE. Individuals with AD had a higher risk of VTE than controls [adjusted hazard ratio (aHR) 1.17, 95% confidence interval (CI) 1.12-1.22]. When assessing VTE components, AD was associated with a higher risk of DVT (aHR 1.30, 95% CI 1.23-1.37) but not PE (aHR 0.94, 95% CI 0.87-1.02). The VTE risk was greater in older people with AD (≥ 65 years: aHR 1.22, 95% CI 1.15-1.29; 45-65 years: aHR 1.15, 95% CI 1.05-1.26; < 45 years: aHR 1.07, 95% CI 0.97-1.19) and those with obesity [body mass index (BMI) ≥ 30: aHR 1.25, 95% CI 1.12-1.39; BMI < 30: aHR 1.08, 95% CI 1.01-1.15). Risk was broadly consistent across mild, moderate or severe AD.

Conclusions: AD is associated with a small increase in risk of VTE and DVT, with no increase in risk of PE. The magnitude of this risk increase is modest in younger people, and those without obesity.