Inflammatory markers and niacin skin flush response in men with chronic schizophrenia

To investigate the relationships among inflammatory cytokines, niacin skin sensitivity, and clinical symptoms of male patients with chronic schizophrenia.

The cohort included 80 male inpatients with chronic schizophrenia (illness duration ≥5 years, clinically stable) and 40 demographically matched healthy controls. Serum levels of inflammatory cytokines (IL-1α, IL-6, TNF-α, IFN-γ) were measured using Luminex technology. The niacin skin flush response (NSFR) was assessed using filter paper saturated with aqueous methylnicotinate (0.01 mol/L, scored at 10 min). Clinical symptoms were evaluated using the Positive and Negative Syndrome Scale (PANSS).

As compared to controls, the NSFR of patients was significantly attenuated (p < 0.001). While IL-1α levels were comparable, patients had significantly elevated serum levels of IL-6, TNF-α, and IFN-γ (p < 0.001, Bonferroni-corrected). In the patient group, serum IL-6 level was positively correlated with PANSS positive subscale score (r = 0.316, adjusted p = 0.016) and PANSS total score (r = 0.347, adjusted p = 0.008). Patients were stratified into high- and low-NSFR groups. Binary logistic regression identified IFN-γ as a significant independent correlate of a low NSFR (β = 0.116, p < 0.001, OR = 1.123), after controlling for demographic and clinical variables.

Male patients with chronic schizophrenia demonstrate concurrent peripheral inflammatory cytokine elevation and impaired niacin sensitivity. The association between elevated IFN-γ levels and a reduced NSFR suggests a link between inflammatory imbalance and this established endophenotype. These findings contribute to a clearer understanding of the role of immune dysregulation in the pathophysiology of chronic schizophrenia.