Risk of hospitalization and death due to infection in people with psoriasis: a population-based cohort study using the Clinical Practice Research Datalink

Background: Psoriasis is associated with risk factors for serious infections, but the independent relationship between psoriasis and serious infection is as yet unclear.

Objectives: To determine whether people with psoriasis have a higher risk of hospitalization due to any infection, respiratory infections, soft-tissue and skin infections, or a higher risk of death due to infection.

Methods: We conducted a cohort study of people (≥ 18 years) with psoriasis using the UK Clinical Practice Research Datalink (CPRD GOLD) linked to Hospital Episode Statistics (HES) and Office for National Statistics (ONS) mortality records between 1 April 2003 and 31 December 2016, and matched with up to six comparators on age, sex and general practice. Hospitalization was ascertained from HES records; death was ascertained from ONS mortality records. Stratified Cox proportional hazard models were estimated, with stepwise adjustment in different models for potential confounders or mediators between psoriasis and serious infection.

Results: There were 69 315 people with psoriasis and 338 620 comparators who were followed up for a median (interquartile range) of 4·9 (5·9) and 5·1 (6·3) years, respectively. People with psoriasis had a higher incidence rate of serious infection [20·5 per 1000 person-years, 95% confidence interval (CI) 20·0-21·0, n = 7631] compared with those without psoriasis (16·1 per 1000 person-years, 95% CI 15·9-16·3, n = 30 761). The fully adjusted hazard ratio for the association between psoriasis and serious infection was 1·36 (95% CI 1·31-1·40), with similar results across the other outcomes.

Conclusions: Psoriasis is associated with a small increase in the risk of serious infection. Further research is needed to understand how psoriasis predisposes to a higher risk of infection.