Low-Grade Inflammation Increases Risk of Psoriasis, Especially in Severe Cases: Study Finds

Inflammatory markers—such as the systemic immune-inflammation index (HR 1.78), neutrophil-to-lymphocyte ratio (HR 1.56), and C-reactive protein (HR 2.83)—were identified as independent predictors of psoriasis, underscoring their potential role in its pathogenesis. Traditionally linked to cardiovascular and metabolic disorders, these biomarkers now appear to play a key role in the development of this chronic inflammatory skin condition.

Biomarkers of low-grade systemic inflammation are often elevated in individuals with psoriasis compared to healthy individuals. However, it has remained unclear whether this inflammation plays a causal role in the development of psoriasis or is simply a result of the disease. To address this, Charlotte Näslund-Koch, Department of Clinical Medicine, Copenhagen University, Copenhagen, Denmark, and colleagues aimed to determine whether low-grade systemic inflammation—assessed through indicators such as the systemic immune-inflammation index (SII), neutrophil-to-lymphocyte ratio (NLR), and C-reactive protein (CRP)—serves as an independent risk factor for the onset of psoriasis.

For this purpose, the researchers analyzed data from the Copenhagen General Population Study, enrolling adults aged 20–100 between 2003 and 2015. Participants underwent physical exams, completed lifestyle questionnaires, and provided blood samples to measure SII, NLR, and CRP. Psoriasis cases were identified using ICD codes from national health records. Associations were assessed using Cox regression models, adjusting for age, sex, smoking, alcohol use, physical activity, education, hypertension, dyslipidemia, and obesity.

The study revealed the following findings:

• The study included 105,418 individuals with a median age of 58 years, 55% of whom were women.
• Higher levels of systemic immune-inflammation index (SII), neutrophil-to-lymphocyte ratio (NLR), and C-reactive protein (CRP) were associated with an increased risk of developing psoriasis.
• Individuals with values above the 90th percentile for SII, NLR, and CRP had multivariable adjusted hazard ratios of 1.78, 1.56, and 2.83, respectively, compared to those with lower levels.
• These associations remained consistent, though slightly reduced, when considering cases of mild psoriasis treated with topical calcipotriol (alone or with corticosteroids).

Low-grade systemic inflammation—reflected by elevated levels of systemic immune-inflammation index, neutrophil-to-lymphocyte ratio, and C-reactive protein (CRP)—was found to be independently associated with an increased risk of developing psoriasis in a large population-based study. The risk was particularly pronounced in individuals with moderate-to-severe disease.

"These findings strengthen the hypothesis that chronic low-grade inflammation may actively contribute to the development of psoriasis, rather than being merely a result of the condition," the authors concluded.

Reference:

Bojesen, S. E., Skov, L., & Kobylecki, C. J. Low-grade systemic inflammation is associated with risk of psoriasis in a general population study of more than 100,000 individuals. British Journal of Dermatology. https://doi.org/10.1093/bjd/ljaf147