of nearly 95,000 patients.
Although previous studies have shown a higher risk for comorbid conditions in people with psoriasis, compared with those without psoriasis, data on the occurrence of severe and rare infections in patients with psoriasis are limited, wrote Nikolai Loft, MD, of the department of dermatology and allergy, Copenhagen University Hospital, Gentofte, and colleagues.
Psoriasis patients are often treated with immunosuppressive therapies that may promote or aggravate infections; therefore, a better understanding of psoriasis and risk of infections is needed, they said. In a study published in the British Journal of Dermatology, Dr. Loft and his coinvestigators reviewed data on adults aged 18 years and older from the Danish National Patient Register between Jan. 1, 1997 and Dec. 31, 2018. The study population included 94,450 adults with psoriasis and 566,700 matched controls. Patients with any type of psoriasis and any degree of severity were included.
The primary outcome was the occurrence of severe infections, defined as those requiring assessment at a hospital, and rare infections, defined as HIV, TB, HBV, and HCV. The median age of the participants was 52.3 years, and slightly more than half were women.
Overall, the incidence rate of severe and rare infections among patients with any type of psoriasis was 3,104.9 per 100,000 person-years, compared with 2,381.1 for controls, with a hazard ratio, adjusted for gender, age, ethnicity, socioeconomic status, alcohol-related conditions, and Charlson comorbidity index (aHR) of 1.29.
For any infections resulting in hospitalization, the incidence rate was 2,005.1 vs. 1,531.8 per 100,000 person-years for patients with any type of psoriasis and controls, respectively.
The results were similar when severe infections and rare infections were analyzed separately. The incidence rate of severe infections was 3,080.6 and 2,364.4 per 100,000 person-years for patients with any psoriasis, compared with controls; the incidence rate for rare infections was 42.9 and 31.8 for all psoriasis patients and controls, respectively.
When the data were examined by psoriasis severity, the incidence rate of severe and rare infections among patients with severe psoriasis was 3,847.7 per 100,000 person-years, compared with 2,351.9 per 100,000 person years among controls (aHR, 1.58) and also higher than in patients with mild psoriasis. The incidence rate of severe and rare infections in patients with mild psoriasis (2,979.1 per 100,000 person-years) also was higher than in controls (aHR, 1.26).
Factors that might explain the increased infection risk with severe psoriasis include the altered immune environment in these patients, the researchers wrote in their discussion of the findings. Also, “patients with severe psoriasis are defined by their eligibility for systemics, either conventional or biologic,” and their increased infection risk may stem from these treatments, rather than disease severity itself, they noted.
The study findings were limited by several factors including the lack of data on such confounders as weight, body mass index, and smoking status, they added. Other limitations included potential surveillance bias because of greater TB screening, and the use of prescriptions, rather than the Psoriasis Area Severity Index, to define severity. However, the results were strengthened by the large sample size, and suggest that patients with any type of psoriasis have higher rates of any infection, severe or rare, than the general population, the researchers concluded.