Association between metabolic syndrome, cognitive dysfunctions, and peripheral inflammation in schizophrenia

TL;DR

This study finds that metabolic syndrome in schizophrenia patients is linked to worse attention and delayed memory, possibly due to peripheral inflammation.

Contribution

The study provides new evidence that peripheral inflammation may mediate the cognitive effects of metabolic syndrome in schizophrenia.

Findings

Patients with MetS showed worse attention and delayed memory compared to those without MetS.

Higher IL-6 levels were associated with worse delayed memory.

The cognitive effects of MetS were limited in scope and had small effect sizes.

Abstract

Metabolic syndrome (MetS) is of primary clinical interest because of its harmful impact on the general health and quality of life of patients with psychotic disorders. Paradoxically, MetS is associated with impaired cognitive functions in patients receiving antipsychotics primarily shown to improve cognition (e.g., clozapine and olanzapine).

In this study, we aimed to investigate the relationship between MetS, cognitive functions, and peripheral inflammation.

The participants were 154 patients with schizophrenia. Fifty-seven patients met the criteria of MetS. We evaluated cognitive functions with the Repeated Battery for the Assessment of Neuropsychological Status (RBANS). The Positive and Negative Syndrome Scale (PANSS) quantified the clinical symptoms. We also measured the plasma levels of IL-6 and C-reactive protein (CRP). In addition to conventional statistics, we also calculated Cohen’s effect size (d) and Bayes Factors (BF10).

Results revealed that patients with MetS exhibited worse cognitive function relative to patients without Mets in attention (d = 0.19, BF10 = 2.3) and delayed memory (d = 0.25, BF10 = 5.7). No significant between-group differences existed in immediate memory, visuospatial functions, and language. The MetS and non-MetS groups did not differ in positive, negative, or general symptoms. Higher IL-6 levels were associated with worse delayed memory (r=-0.56, BF10=34.6).

Our results suggest that MetS-associated cognitive dysfunctions are less severe than reported in the literature: it was confined to two cognitive domains, the effect size was small, and the Bayesian evidence level was weak. Peripheral inflammation may mediate the association between MetS and long-term memory dysfunctions.

None Declared