Determinants of pro- and anti-inflammatory cytokine profiles across populations.
BACKGROUND: Cytokine dysregulation contributes to chronic inflammation and immune-mediated diseases, yet population-level determinants of pro- and anti-inflammatory cytokines remain poorly characterized. We aimed to identify demographic and lifestyle determinants of plasma cytokine levels and evaluate reproducibility of inflammatory patterns across European populations. METHODS: In the population-based Rotterdam Study cohort (n = 3,456; mean age 57 years; 56% female), we examined associations between plasma levels of nine cytokines (Olink Inflammation Panel) and age, sex, smoking, body mass index (BMI), and alcohol consumption. Linear and non-linear regression models were applied, with stratified analyses where appropriate. Cytokine clustering was assessed using principal component analysis (PCA). Findings were replicated in two independent European cohorts using identical protocols. Additionally, associations between raw IL-6 levels and determinants were meta-analyzed across the two replication cohorts (total n > 4,000). RESULTS: Plasma IL-10, IL-6, IL-17 A, TNF, IFN-γ, IL-18, and IL-17 C increased with age; IL-18 and IL-17 C followed non-linear trends (P < 0.01). Females had lower IL-18 and IL-17 C levels (β: - 0.41 and - 0.32, respectively) but higher IFN-γ (β: 0.17). Smoking was associated with higher IL-10, IL-6, IL-18, and IL-17 C (β range: 0.10-0.54) and lower IFN-γ (β: -0.15) and IL-13 (β: - 0.10). BMI was positively associated with IL-6, IL-18, TNF, and IL-17 A levels (P < 0.05), and inversely with IL-10 (P < 0.001). Sex-specific associations were observed for alcohol use. PCA revealed stable pro-inflammatory cytokine clustering, consistent across cohorts. Replication in analyses confirmed a robust, shared pro-inflammatory signature, and meta-analysis supported consistent associations with older age, higher BMI, and current smoking. CONCLUSIONS: Older age, higher BMI, male sex, and current smoking are consistent and reproducible determinants of inflammatory cytokine profiles across European populations. These findings support the use of cytokine profiling in enhancing risk stratification for inflammation-related diseases.