Association between fasting insulin levels and cognitive impairment in patients with first-episode drug-naïve schizophrenia: a large-scale cross-sectional study.

Previous studies have primarily investigated the adverse effects of insulin resistance (IR) on cognitive function in schizophrenia (SZ) patients. IR is typically assessed based on fasting insulin (FINS) and fasting blood glucose (FBG) levels. This study revealed that first-episode, drug-naïve (FEND) SZ patients had normal FBG levels, with no significant difference from healthy controls, while significantly elevated FINS levels, indicating that IR in FEND SZ patients may be predominantly driven by increased FINS. This study primarily investigated the association between FINS levels and cognitive impairment in FEND SZ patients. This cross-sectional research recruited 466 FEND SZ patients. The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was utilized to evaluate participants' neurocognitive performance, and measured the levels of FINS, FBG, and glycated hemoglobin. The link between FINS and cognitive performance was evaluated using multiple linear regression and smoothing curve fitting methods. After adjusting for relevant confounding factors, FINS were negatively correlated with immediate memory (β = -7.77), attention (β = -9.09), delayed memory (β = -13.02), and total RBANS scores (β = -5.21) (all p < 0.001). Quartile analysis revealed that elevated FINS were linked to decreased cognitive function scores. (all p < 0.001). In FEND SZ patients, higher FINS levels are associated with more severe cognitive impairment, suggesting that FINS may be indicative of evaluating cognitive impairment as a potential biomarker. Measurement of pre-treatment FINS at the initial clinical visit is of important clinical value for guiding therapeutic interventions to improve insulin sensitivity and, consequently, patients' cognitive function.