Non-verbal cognitive domain functions positively associate with mildly elevated fasting blood glucose in individuals presenting with a psychotic illness

• Author / Creator

  Sivapalan, Sudhakar

• Background: The metabolic syndrome (MetS) is a cluster of biological parameters that have been identified as significant risk factors in the development of cardiovascular disease. The relevance of MetS to the psychiatric population has been demonstrated in that having severe mental illness (SMI) itself and also being prescribed antipsychotic medications contribute to the development of MetS. A review of published investigations of non-geriatric general populations suggested that memory, executive functioning, processing speed, and general intellect may be affected by having MetS, with specific MetS factors appearing to correlate with domain-specific cognitive changes. However, the non-geriatric studies tended to sample older populations and thus remain limited with respect to generalization to children, adolescents and young adults. This study is an exploration of the relationship between MetS and cognitive functioning in a younger population with a psychotic illness. Based on a review of the literature, we hypothesized that individuals with a psychotic illness and meeting criteria for a diagnosis of MetS would have increased cognitive dysfunction in one or more domains, in addition to the effects of having a psychotic illness alone. Additionally, we expected impairment in glucose regulation to be associated with impairment of attention and processing speed, and obesity to be associated with impairments in attention, working memory, and visuospatial skills. Methods: Individuals presenting with early psychosis (having less than one year of treatment) to the Edmonton Early Psychosis Intervention Clinic in Edmonton, Alberta were assessed with the MATRICS Consensus Cognitive Battery (MCCB). Clinical assessment also included an evaluation of the factors of MetS as defined by the National Cholesterol Education Programs Adult Treatment Panel III (NCEP-ATP III) criteria. Following an exploratory analysis, linear regression analysis was used to identify possible significant relationships between discrete markers of MetS, such as fasting blood glucose, and specific cognitive domains. Results: As only two individuals met criteria for MetS, we moved to analysis of discrete markers of MetS and specific cognitive assessments. Fasting blood glucose levels were positively associated with spatial working memory (Wechsler Memory Scale-III: Spatial Span) (β = 0.33; t= 2.36; p = 0.02), recall of figures (Brief Visuospatial Memory Test - Revised) (β = 0.30; t =2.15; p = 0.04), and a measure of reasoning and problem solving (Neuropsychological Assessment Battery ®: Mazes) (β = 0.34; t = 2.41; p = 0.02). Covariates, such as occupational status, socioeconomic status, years of education, cannabis use, and medication effects did not appear to exert any significant effect on these relationships. Discussion: This analysis demonstrated that fasting blood glucose values were generally within the normal range in this young sample of individuals suffering a first episode of psychosis, and not associated with measures of sustained attention or processing speed. Fasting blood glucose values were, however, directly associated with performance on several non-verbal tasks sensitive to spatial working memory, learning and memory of designs, and executive skills related to reasoning and problem solving with spatial materials. This relationship was not predicted, but the consistency across non-verbal instruments suggests a potentially reliable effect that may implicate relatively circumscribed cerebral effects of glucose in relation to relevant neuroanatomy, and to the shifting pattern of cerebral blood flow during cognitive tasks. Although provocative, replication will be necessary to gain confidence in the stability of this result and the validity of inferences regarding potential mechanisms that might underlie this association.

• Subjects / Keywords

  • metabolic syndrome
  • severe mental illness
  • first episode psychosis
  • cognition
  • MATRICS Consensus Cognitive Battery

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3610W799

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.