Tea Consumption Reduces the Incidence of Neurocognitive Disorders: Findings from the Singapore Longitudinal Aging Study.

OBJECTIVES: To examine the relationships between tea consumption habits and incident neurocognitive disorders (NCD) and explore potential effect modification by gender and the apolipoprotein E (APOE) genotype. DESIGN: Population-based longitudinal study. SETTING: The Singapore Longitudinal Aging Study (SLAS). PARTICIPANTS: 957 community-living Chinese elderly who were cognitively intact at baseline. MEASUREMENTS: We collected tea consumption information at baseline from 2003 to 2005 and ascertained incident cases of neurocognitive disorders (NCD) from 2006 to 2010. Odds ratio (OR) of association were calculated in logistic regression models that adjusted for potential confounders. RESULTS: A total of 72 incident NCD cases were identified from the cohort. Tea intake was associated with lower risk of incident NCD, independent of other risk factors. Reduced NCD risk was observed for both green tea (OR=0.43) and black/oolong tea (OR=0.53) and appeared to be influenced by the changing of tea consumption habit at follow-up. Using consistent non-tea consumers as the reference, only consistent tea consumers had reduced risk of NCD (OR=0.39). Stratified analyses indicated that tea consumption was associated with reduced risk of NCD among females (OR=0.32) and APOE ε4 carriers (OR=0.14) but not males and non APOE ε4 carriers. CONCLUSION: Regular tea consumption was associated with lower risk of neurocognitive disorders among Chinese elderly. Gender and genetic factors could possibly modulate this association.

Impact of duration of untreated psychosis and premorbid intelligence on cognitive functioning in patients with first-episode schizophrenia.

BACKGROUND: The neurotoxic hypothesis suggests that psychosis is toxic to the brain leading to clinical consequences. In this study, we hypothesized that a longer duration of untreated psychosis (DUP) in first episode schizophrenia (FES) patients is associated with poorer cognitive functioning, and that higher premorbid intelligence buffers against DUP-related cognitive impairment. METHOD: Eighty-one FES patients completed a neuropsychological battery, the Brief Assessment of Cognition in Schizophrenia (BACS). Composite scores of the BACS, which were normalized to a matched healthy control of seventy-three subjects, were used as an index of general cognition. A median split using the Wide Range Achievement Test-Reading Test scores was used to divide the patients into low versus high premorbid IQ groups. Hierarchical linear regression was performed to examine predictors of general cognition, including DUP. RESULTS: Longer DUP was found to be a significant predictor of poorer general cognition. In addition, DUP predicted general cognition in the low premorbid IQ group but not in the high premorbid IQ group. CONCLUSIONS: Our findings demonstrate that longer DUP in FES patients is associated with worse cognitive scores, and that this association is more pronounced in a subgroup of patients who have lower premorbid intelligence. Our results suggest the importance of earlier identification and management of patients with low premorbid IQ, given that their cognition may be more vulnerable to the toxicity of psychosis.

Refining the latent structure of neuropsychological performance in schizophrenia.

BACKGROUND: Elucidating the cognitive architecture of schizophrenia promises to advance understanding of the clinical and biological substrates of the illness. Traditional cross-sectional neuropsychological approaches differentiate impaired from normal cognitive abilities but are limited in their ability to determine latent substructure. The current study examined the latent architecture of abnormal cognition in schizophrenia via a systematic approach. METHOD: Exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were carried out on a large neuropsychological dataset including the Brief Assessment of Cognition in Schizophrenia, Continuous Performance Test, Wisconsin Card Sorting Test, Benton Judgment of Line Orientation Test, and Wechsler Abbreviated Scale of Intelligence matrix reasoning derived from 1012 English-speaking ethnic Chinese healthy controls and 707 schizophrenia cases recruited from in- and out-patient clinics. RESULTS: An initial six-factor model fit cognitive data in healthy and schizophrenia subjects. Further modeling, which accounted for methodological variance between tests, resulted in a three-factor model of executive functioning, vigilance/speed of processing and memory that appeared to best discriminate schizophrenia cases from controls. Factor analytic-derived g estimands and conventionally calculated g showed similar case-control discrimination. However, agreement analysis suggested systematic differences between both g indices. CONCLUSIONS: Factor structures derived in the current study were broadly similar to those reported previously. However, factor structures between schizophrenia subjects and healthy controls were different. Roles of factor analytic-derived g estimands and conventional composite score g were further discussed. Cognitive structures underlying cognitive deficits in schizophrenia may prove useful for interrogating biological substrates and enriching effect sizes for subsequent work.

Asymmetry of lexico-semantic processing in schizophrenia changes with disease progression.

BACKGROUND: Are anomalies of cerebral asymmetry integral to the disease process? Here, we examined the influence of age, chronicity and age of onset of illness in 34 patients with early onset schizophrenia and 20 controls in relation to structural asymmetries of the temporal lobe and performance asymmetries on a semantic language lexical decision task. METHODS: Volumetric MRI and a novel divided visual field probe of lateralised lexico-semantic language were assessed in patients with early onset schizophrenia (EOS) and controls. Novel ratios of age-illness overlap and directional asymmetry were developed in order to examine the association of chronicity factors to asymmetry. RESULTS: Loss of laterality on the lexical decision task and discordant structural asymmetry were correlated with duration of illness but were not seen in younger, less chronic patients. Reduced lateral processing speed, and discordant structural asymmetry were associated with greater proportion of lifetime schizophrenia. CONCLUSION: Although the conclusions are limited by the cross sectional nature of the study, anomalies of cerebral asymmetry in early onset patients may be an index of disease progression, and reflect directly on the disease process.

The utility and benefits of clinical neuropsychology in Asia.

Neuropsychological evaluation is the clinical practice of identifying and measuring impairments in mental functions in the context of a patient's mental strengths and preserved abilities for the purposes of diagnosis, rehabilitation planning, and long-term care. Best practice approaches to the medical management of neurodegenerative, neurological and psychiatric illness have lead to increasing demand for neuropsychological services. The simultaneous challenges of Asias' increasing adult and rapidly ageing population underscore the need for consideration of the role of neuropsychological services in day-to-day clinical practice. Here, we outline the clinical utility of neuropsychological assessment and indications for its use in general psychiatric practice.

Verbal fluency in schizophrenia: relationship with executive function, semantic memory and clinical alogia.

To examine whether poor verbal fluency in schizophrenia represents a degraded semantic store or inefficient access to a normal semantic store, 25 normal volunteers and 50 DSM-III-R schizophrenic patients, matched for age, sex and IQ, were recruited. Although schizophrenic patients were impaired on both letter and category fluency, they showed a normal pattern of output in that category was superior to letter fluency, and an improvement in category fluency when a cueing technique was employed (Randolph et al. 1993). These results resemble those found in disorders of frontostriatal systems (Parkinson's and Huntington's disease) and suggest that poor verbal fluency in schizophrenia is because of inefficient access to semantic store. A measure of improvement with cueing was directly related to performance on the Stroop executive task. Of all symptom measures derived from SANS and Manchester Scales, only alogia was related to verbal fluency in that superior improvement correlated inversely with the degree of alogia. It is suggested that both alogia and poor verbal fluency are mediated by the same underlying cognitive abnormality that reflects frontostriatal dysfunction.