Is platelet activation a link between metabolic syndrome and cognitive impairment in patients with schizophrenia?

IntroductionSchizophrenia is a severe psychiatric condition associated with cognitive impairment and premature dementia. Furthermore, metabolic syndrome (MetS)--combined central obesity, diabetes, dyslipidemia and hypertension--is highly prevalent in patients with schizophrenia and is believed to contribute to cognitive impairment and premature dementia in patients with schizophrenia. However, the mechanisms by which MetS contributes to cognitive impairment in patients with schizophrenia is unclear. Based on the association of MetS with platelet activation and the ability of activated platelets to impact blood-brain-barrier function, we tested the hypothesis that platelet activation is associated with both MetS and cognitive impairment in two independent pilot samples of patients with schizophrenia. MethodsIn the first pilot sample (sample A) we recruited 13 veterans with either schizophrenia or schizoaffective disorder with MetS (MetS+, n=6), and without MetS (MetS-, n=7). We administered the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery (MCCB) on all 13 veterans and assessed platelet activation using flow cytometry. In the second pilot sample (sample B), we identified 10 non-veteran MetS+ patients with schizophrenia and 10 age-, and sex-matched MetS-patients with schizophrenia from previously collected data on 106 patients enrolled in a non-MetS study. Participants in sample B had data on the NIH Toolbox cognitive battery (NIH Toolbox) and plasma soluble P-selectin (sP-selectin), a marker of platelet activation. We compared flow cytometry platelet activation in MetS+ and MetS- using the Mann Whitney test and the median test to compare sP-selectin and cognitive measures. We also measured the correlation between platelet activation and cognition using Spearmans rho correlation. ResultsPlatelet activation was significantly higher in MetS+ than MetS- (mean rank 8.60 vs. 3.83, p=0.017). Median score for the picture vocabulary test (language ability) was significantly lower in MetS+ relative to MetS- (82.35 vs. 104, p=0.015). In addition, platelet activation correlated negatively (rho = -0.74, p= 0.009) with the Wechsler Memory Scale: Spatial Span (nonverbal working memory) and plasma sP-selectin correlated negatively (rho = -0.55, p= 0.029) with the List Sorting Working Memory Test. ConclusionOur preliminary findings suggest that platelet activation is involved in the association of MetS with cognitive impairment in patients with schizophrenia. Future studies are needed to elucidate the role of platelets in MetS-related cognitive impairment in patients with schizophrenia.