Association between inflammatory score and incident cancer risk among middle-aged and older Chinese adults: a prospective cohort study from CHARLS.

BACKGROUND: Chronic inflammation is a recognized driver of carcinogenesis. The inflammatory score, a composite metric integrating C-reactive protein (CRP) and white blood cell (WBC) counts, offers a systematic assessment of systemic inflammatory burden. However, prospective evidence linking inflammatory score (IS) with new-onset cancer in the general population remains limited. METHODS: We included 8650 cancer-free participants aged ≥ 45 years from the China Health and Retirement Longitudinal Study (CHARLS) baseline survey (2011). The IS was calculated as the sum of Z-scores for CRP and WBC. Incident cancer was ascertained through follow-up waves (2013, 2015, and 2018). Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI). Restricted cubic spline (RCS) regression was applied to evaluate the dose-response relationship. Subgroup, sensitivity, and E-value analyses were performed to assess robustness. RESULTS: During follow-up, 182 new-onset cancer cases were identified. In the fully adjusted model, each one-unit increment in inflammatory score was associated with an 8.8% increased risk of new-onset cancer (HR = 1.088, 95% CI: 1.011-1.170; p = 0.024). RCS analysis revealed a linear dose-response relationship (P for non-linearity = 0.770). The association remained consistent across subgroups defined by age, sex, smoking, and alcohol consumption (all P for interaction > 0.05). Sensitivity analysis excluding events occurring within the first 4 years attenuated the association (HR = 1.018, 95% CI: 0.911-1.137), suggesting a relatively stronger short-term risk contribution. The E-value was 1.397 (lower limit of the 95% CI: 1.118), indicating moderate robustness to unmeasured confounding. CONCLUSIONS: Higher baseline inflammatory score is independently associated with an elevated risk of new-onset cancer among middle-aged and older Chinese adults. The inflammatory score may serve as an accessible composite biomarker for cancer risk stratification and early prevention.