Hyperlipidemia correlated with better neurocognition in patients with schizophrenia

Cognitive dysfunction is a core feature of schizophrenia and is associated with functional dysfunction. It is generally believed that metabolic abnormalities may further impair neurocognition in schizophrenia. This study analyzed prospective data from the NIMH-funded schizophrenia CATIE study to examine the effects of hyperlipidemia on neurocognitive measures. We hypothesized that higher cholesterol and triglyceride levels are correlated with lower cognitive performance.

Screening data was collected on 1460 patients, including demographics, psychiatric history, and metabolic variables. Serum cholesterol and triglycerides were measured in a subsample (N = 741, mean age 40.4 years, 75% male, 61% white) who were in a fasting (≥ eight hours) state. Neurocognition was assessed at baseline using the Neurocognitive Composite (NC) Score, an average of five composite subscale z-scores: 1) Processing Speed 2) Verbal Memory 3) Vigilance Summary Score 4) Reasoning Summary Score 5) Working Memory Summary Score. Regression and analysis of variance models were used to examine the relationships between metabolic variables and neurocognition.

Patients with low HDL cholesterol levels had significantly lower NC scores than patients with high HDL levels (p = 0.04). Conversely, contrary to our hypothesis, patients with elevated total cholesterol had significantly higher NC scores than patients with low total cholesterol (p = 0.002). Similarly, participants with elevated triglycerides had significantly higher NC scores when compared to participants with low triglycerides (p = 0.02).

Our study found that high fasting cholesterol and triglyceride levels correlated with better neurocognition in patients with schizophrenia. The clinical and research implications of these unexpected findings are discussed.