Association Between Systemic Inflammation Response Index and All-Cause Mortality in Individuals with Chronic Pain:...

Chronic pain is a common condition that has been linked to systemic inflammation. In recent years, the system inflammation response index (SIRI) has aroused researchers' interest as a novel inflammatory biomarker. The association between SIRI and mortality in individuals with chronic pain remains unclear.

To explore the association between SIRI and all-cause mortality in individuals with chronic pain, and to assess the index's potential as a tool for risk stratification in this population.

A population-based prospective cohort study.

The National Health and Nutrition Examination Survey (NHANES) 1999-2004, with mortality follow-up through December 31, 2019.

Cox proportional hazards regression models were employed to evaluate the association between log10-transformed SIRI and all-cause mortality in the chronic pain population, adjusting for demographic and health-related factors. To handle missing data, multiple imputation by chained equations was performed, generating 5 imputed datasets. Nonlinear relationships were examined using restricted cubic spline (RCS) regression and piecewise models to explore potential threshold effects.

The study included 1,938 patients with chronic pain, of whom 647 died during follow-up. Higher log10(SIRI) was associated with higher all-cause mortality in fully adjusted models (hazard ratio [HR] per one-unit increase, 2.56; 95% confidence interval [CI], 1.67-3.94; P < 0.001). Compared to patients in the lowest SIRI tertile, those in the highest tertile had a higher mortality risk (HR, 1.45; 95% CI, 1.11-1.90; P < 0.001). RCS analyses further suggested a nonlinear association between SIRI and mortality, with a steeper increase in risk at higher SIRI levels. The association appeared stronger among adults aged ≥ 52 years.

Chronic pain status was self-reported using a duration-based definition (≥ 3 months) and lacked detailed clinical characterization and treatment data.

In adults with chronic pain, higher SIRI was associated with a higher risk of all-cause mortality, with a more pronounced association in older adults. SIRI may be useful for mortality risk stratification in this population.