Although previous studies suggest that psoriasis may be independently associated with an increased risk of serious infection—that which leads to hospitalization—the research had various limitations, and thus, the relationship remains unclear, explains Zenas Yiu, PhD. In a study published in the British Journal of Dermatology, Dr. Yiu and colleagues sought to determine if patients with psoriasis, when compared with those without the condition, have a higher risk of hospitalization due to any infection, respiratory infections, soft tissue and skin infections, or death due to infection.

Using data from the nationally representative UK Clinical Practice Research Datalink linked to Hospital Episode Statistics (HES) and Office for National Statistics (ONS) mortality records between January 2003 and December 2016, the researchers matched adults with psoriasis with up to six comparators on age, sex, and general practice. Hospitalization due to infection was ascertained from HES records and death from ONS mortality records. Stratified Cox proportional hazard models were estimated, with stepwise adjustment in different models for confounding factors, including body mass index, smoking, alcohol intake, socioeconomic status, and comorbid conditions. Approximately 70,000 patients with psoriasis and nearly 340,000 comparators were followed for a median of about 5 years.

“People with psoriasis had a higher incidence rate of serious infection, at 20.5 per 1,000 person-years, than the comparators, at 16.1 per 1,000 person-years,” says Dr. Yiu. “After adjustment, people with psoriasis had a 36% increased relative probability of developing a serious infection during follow-up compared with the general population (hazard ratio, 1.36). However, this only translated to three out of 100 more people with psoriasis developing a serious infection after 10 years of follow-up, compared with the general population.”

Dr. Yiu notes that while patients with psoriasis were found to have a small but increased risk of serious infection when compared with those without the condition, “because the absolute increased probability of serious infection is small, people with psoriasis should not be unduly concerned. We recommend further research to investigate whether this slight increase in the risk of infection can be explained by biological mechanisms.”