A longitudinal study of cognition in asymptomatic and mildly symptomatic bipolar disorder patients

A one-year view on the association of metabolic syndrome and cognitive function in bipolar disorder - Preliminary data

BACKGROUND

Individuals with bipolar disorder have a high prevalence of metabolic syndrome and an increased risk for cognitive deficits. The aim of this longitudinal study was to investigate the trajectory of cognitive decline in dependence of metabolic syndrome over a one-year interval.

METHODS

52 well-diagnosed individuals with bipolar disorder, euthymic at baseline and follow-up (n = 17 with metabolic syndrome vs. n = 35 without metabolic syndrome) were investigated with a comprehensive neurocognitive test battery (Trail Making Test A/B, Digit Symbol Test, California Verbal Leaning Test, or the Verbal Learning and Memory Test respectively) twice within the interval of one year.

RESULTS

Patients with bipolar disorder and additional metabolic syndrome performed significantly worse in the domain of psychomotor and processing speed/attention than patients without metabolic syndrome at test point one. No deteriorating effects of metabolic syndrome on the cognitive domain scores and overall cognitive performance were found at the one-year follow up. However, no cognitive decline could be reported in both groups.

LIMITATIONS

Time interval, small sample size and selection of metabolic syndrome affected patients were the major limitations of this study.

CONCLUSION

There was no association of metabolic syndrome on the one-year trajectory of cognitive function in bipolar disorder. Future studies should expand the observation period and investigate larger samples.

Cognitive Impairment Mechanism in Patients with Bipolar Disorder

Bipolar disorder (BD) is a common chronic mental disorder usually characterized by manic, hypomanic and depressive episodes. Patients diagnosed with BD have cognitive impairments in both the mood attack and remission stages, that is impairment of attention, memory and executive function. Up till the present moment, the causative mechanisms of cognitive impairment in BD patients remain poorly understood. Several studies have demonstrated that cognitive impairment in patients with bipolar disorder is not associated with a single factor, but with gene polymorphism, brain structural and functional variables, inflammatory and metabolic factors. Herein, we reviewed and summarized the recent reports on cognitive impairment mechanisms in patients with BD. To prevent or alleviate cognitive damage at an early stage, we propose that future research should focus on investigating the pathological mechanism of specific cognitive dimension damage as well as the pathological mechanism network between the damage of each dimension. It is crucial to recognize mechanisms of cognitive impairment for improving the symptoms and prognosis of BD patients, restoring their social function and integration.

Neuropsychological aspects of bipolar disorder

Bipolar disorder (BD) is a chronic condition with serious consequences on the health and functionality of patients who suffer from it, with a high heritability and segregation, and aprevalence of between 1% and 2%. Neuropsychological deficits have been implicated as a very important issue related to BD prognosis, so a review was conducted of these deficits, the related factors and their functional consequences. It has been determined that the presence of neuropsychological deficits can vary in patients with BD according to their mood state, with a great influence of depressive symptoms on the cognitive variability of patients with respect to the general population and differences with respect to patients in the manic phase. In euthymic patients, the most affected cognitive domains are those of memory, attention, and executive function, associated with a more severe disease, sociodemographic vulnerability factors, and stable over time. A relationship has been found between poor cognitive performance, especially executive dysfunction, and objective functional deficit. Furthermore, cognitive differences have been outlined between BD and other serious mental illnesses that are described in this review.

Exploring Signatures of Neurodegeneration in Early-Onset Older-Age Bipolar Disorder and Behavioral Variant Frontotemporal Dementia

Introduction: Older-age bipolar disorder (OABD) may involve neurocognitive decline and behavioral disturbances that could share features with the behavioral variant of frontotemporal dementia (bvFTD), making the differential diagnosis difficult in cases of suspected dementia. Objective: To compare the neuropsychological profile, brain morphometry, and structural connectivity patterns between patients diagnosed with bvFTD, patients classified as OABD with an early onset of the disease (EO-OABD), and healthy controls (HC). Methods: bvFTD patients (n = 25, age: 66 ± 7, female: 64%, disease duration: 6 ± 4 years), EO-OABD patients (n = 17, age: 65 ± 9, female: 71%, disease duration: 38 ± 8 years), and HC (n = 28, age: 62 ± 7, female: 64%) were evaluated through neuropsychological tests concerning attention, memory, executive function, praxis, and language. Brain morphometry was analyzed through surface-based morphometry (SBM), while structural brain connectivity was assessed through diffusion tensor imaging (DTI). Results: Both bvFTD and EO-OABD patients showed lower performance in neuropsychological tests of attention, verbal fluency, working memory, verbal memory, and praxis than HC. Comparisons between EO-OABD and bvFTD showed differences limited to cognitive flexibility delayed recall and intrusion errors in the memory test. SBM analysis demonstrated that several frontal, temporal, and parietal regions were altered in both bvFTD and EO-OABD compared to HC. In contrast, comparisons between bvFTD and EO-OABD evidenced differences exclusively in the right temporal pole and the left entorhinal cortex. DTI analysis showed alterations in association and projection fibers in both EO-OABD and bvFTD patients compared to HC. Commissural fibers were found to be particularly affected in EO-OABD. The middle cerebellar peduncle and the pontine crossing tract were exclusively altered in bvFTD. There were no significant differences in DTI analysis between EO-OABD and bvFTD. Discussion: EO-OABD and bvFTD may share an overlap in cognitive, brain morphometry, and structural connectivity profiles that could reflect common underlying mechanisms, even though the etiology of each disease can be different and multifactorial.

Neuropsychological Aspects of Bipolar Disorder

Bipolar disorder (BD) is a chronic condition with serious consequences on the health and functionality of patients who suffer from it, with a high heritability and segregation, and a prevalence of between 1% and 2%. Neuropsychological deficits have been implicated as a very important issue related to BD prognosis, so a review was conducted of these deficits, the related factors and their functional consequences. It has been determined that the presence of neuropsychological deficits can vary in patients with BD according to their mood state, with a great influence of depressive symptoms on the cognitive variability of patients with respect to the general population and differences with respect to patients in the manic phase. In euthymic patients, the most affected cognitive domains are those of memory, attention, and executive function, associated with a more severe disease, sociodemographic vulnerability factors, and stable over time. A relationship has been found between poor cognitive performance, especially executive dysfunction, and objective functional deficit. Furthermore, cognitive differences have been outlined between BD and other serious mental illnesses that are described in the review.

Cognitive Impairment in Patients with Bipolar Disorder: Impact of Pharmacological Treatment

Bipolar disorder is an illness characterised by periods of elated and depressed mood. These mood episodes are associated with changes in cognitive function and there is evidence to suggest that cognitive dysfunction persists during euthymia. The extent to which this is a function of the illness or a result of treatment is less clear. In this narrative review, we explore the impact of commonly used medications for bipolar disorder on cognitive function. Specific impairments in executive function and verbal memory have been noted in bipolar disorder. The impact of pharmacological treatments upon cognitive function is mixed with a number of studies reporting conflicting results. Interpretation of the data is further complicated by the variety of cognitive tests employed, study design, the relatively small numbers of patients included and confounding by indication. Overall, there is some evidence that while lithium improves some cognitive domains, it impedes others. Antipsychotics may be deleterious to cognition, although this may relate to the patient population in which they are prescribed. Sodium valproate is also associated with worse cognitive outcomes, while the impact of other antiepileptics is unclear. Overall the quality of evidence is poor and is derived from a relatively small number of studies that often do not account for the significant heterogeneity of the disorder or common comorbidities. The use of consistent methodologies and measures of cognition across studies, as well as in naturalistic settings, would enable more certain conclusions to be drawn.

Impact of number of episodes on neurocognitive trajectory in bipolar disorder patients: a 5-year follow-up study

BACKGROUND

The neurocognitive trajectory in bipolar disorder (BD) is variable, with controversial findings, and most evidence come from cross-sectional studies. We aimed to examine the course of neurocognitive functioning in a sample of euthymic BD patients in comparison with a control group during a 5-year follow-up.

METHODS

Ninety-nine euthymic bipolar patients and 40 healthy controls were assessed using a comprehensive neurocognitive battery (six neurocognitive domains) at baseline (T1) and then at 5-year follow-up (T2) in a longitudinal study.

RESULTS

No evidence of a progression in neurocognitive dysfunction was found either in cognitive composite index or in any of the neurocognitive domains for the whole cohort. However, there was a negative correlation between number of manic episodes and hospitalisations due to manic episodes and change in neurocognitive composite index (NCI) during the follow-up. Moreover, patients with higher number of manic and hypomanic episodes have a greater decrease in NCI, working memory and visual memory. History of psychotic symptoms was not related to the trajectory of neurocognitive impairment.

CONCLUSIONS

Our results suggest that, although the progression of cognitive decline is not a general rule in BD, BD patients who have a greater number of manic or hypomanic episodes may constitute a subgroup characterised by the progression of neurocognitive impairment. Prevention of manic and hypomanic episodes could have a positive impact on the trajectory of cognitive function.

Assessment of cognitive functions in bipolar I disorder: A 1-year naturalistic follow-up study

OBJECTIVE

Available findings from cross-sectional studies have demonstrated cognitive impairments in bipolar I disorder (BD-I) during various phases of illness. However, very little is known about the longitudinal course of these cognitive impairments. The purpose of the study was to explore the longitudinal pattern of changes in cognitive functioning of BD-I patients.

METHODS

A total of 129 BD-I subjects (manic, depressed and euthymic groups) and 49 healthy controls were recruited using predefined selection criteria. All four study groups were assessed on various clinical and cognitive parameters (for attention, memory, executive functions and working memory) at study intake and at 3-monthly intervals over the next year.

RESULTS

All three patient groups performed poorly compared to controls on all cognitive measures at study intake and on some cognitive measures at the 3-, 6-, 9- and 12-month assessments. No significant time effects were observed for any cognitive test. A significant group by time interaction effect was found for executive functions (β = -44.74; P = .018) and working memory (β = 0.77; P ≤ .019) in the depressed group at 12 months; for visual memory (β = 1.21; P = .039) and working memory (β = 1.17; P ≤ .029) in the manic group at 12 months; and for working memory (β = -0.52; P ≤ .036) in the euthymic group at 12 months.

CONCLUSION

The patient groups showed significant impairments in all or some test domains relative to controls at all time-points. The cognitive functions largely remained stable in all patient groups, with slight improvement over time in a few tests. Further investigation is warranted in larger samples in longitudinal studies.

Cognitive Impairment In Treatment-Naïve Bipolar II and Unipolar Depression

Cognition dysfunction may reflect trait characteristics of bipolarity but cognitive effects of medications have confounded previous comparisons of cognitive function between bipolar II and unipolar depression, which are distinct clinical disorders with some overlaps. Therefore, we examined the executive function (WCST), attention, cognitive speed (TMT-A) and memory (CAVLT, WMS-Visual reproduction) of 20 treatment-naïve bipolar II patients (BPII), 35 treatment-naïve unipolar depressed (UD) patients, and 35 age/sex/education matched healthy controls. The subjects were young (aged 18–35), and had no history of psychosis or substance use, currently depressed and meeting either RDC criteria for Bipolar II Disorder or DSM-IV-TR criteria for Major Depressive Disorder. The patients were moderately depressed (MADRS) and anxious(HAM-A), on average within 3.44 years of illness onset. Sociodemographic data and IQ were similar between the groups. UD patients had significantly slower cognitive speed and cognitive flexibility (WCST perseverative error). BPII depressed patients showed relatively intact cognitive function. Verbal memory (CAVLT List A total) correlated with illness chronicity only in BPII depression, but not UD. In conclusion, young and treatment-naïve BPII depressed patients differed from unipolar depression by a relatively intact cognitive profile and a chronicity-cognitive correlation that suggested a stronger resemblance to Bipolar I Disorder than Unipolar Depression.

Meta-analysis of longitudinal studies of cognition in bipolar disorder: comparison with healthy controls and schizophrenia

BACKGROUND

Bipolar disorder (BP) is associated with significant cognitive impairment. Recent evidence suggests that cognitive deficits are already evident after first-episode mania. However, it is not clear whether BP is associated with further decline in cognitive functions in individuals with established illness. Aim of this meta-analytic review was to examine longitudinal neurocognitive changes in BP and to compare trajectory of cognitive deficits in BP with schizophrenia and healthy controls.

METHODS

Electronic databases were searched for the studies published between January 1987 and November 2016. In total 22 reports were included in the current meta-analysis. The main analysis assessed the longitudinal change in cognition in 643 patients with BP. Further analyses were conducted in studies investigating cognitive changes in BP along with healthy controls (459 BP and 367 healthy controls) and schizophrenia (172 BP and 168 schizophrenia).

RESULTS

There was no cognitive decline overtime neither in short-term (mean duration = 1.5 years) nor in long-term (mean duration = 5.5 years) follow-up studies in BP. In contrast, there was evidence for modest improvements in task performance in memory and working memory at follow-up. The trajectory of cognitive functioning in BP was not significantly different from changes in schizophrenia and healthy controls.

CONCLUSIONS

Together with the findings in early BP and individuals at genetic risk for BP, current findings suggest that neurodevelopmental factors might play a significant role in cognitive deficits in BP and do not support the notion of progressive cognitive decline in most patients with BP.

AnkG hemizygous mice present cognitive impairment and elevated anxiety/depressive-like traits associated with decreased expression of GABA receptors and postsynaptic density protein

Recent genome-wide association studies (GWAS) of patient populations and genetic linkage assessments have demonstrated that the ankyrin-G (AnkG) gene is involved in neuropsychiatric disorders, including bipolar disorder, schizophrenia, and Alzheimer's disease, but it remains unclear how the genetic variants of AnkG contribute to neuropsychiatric disorders. Here, we generated AnkG hemizygous mice using the gene trapping approach. Homozygous AnkG was embryonically lethal. Western blotting and real-time polymerase chain reaction (qPCR) assessments of wild type (WT) and AnkG ^+/- mutant mice demonstrated a 50% reduction of ANKG levels, at the gene and protein levels, in AnkG hemizygous mice. In behavioral tests, AnkG hemizygous mice exhibited elevated anxiety- and depression-like traits, as well as cognitive impairment. Moreover, the expression levels of cognitive-related proteins (including metabotropic glutamate receptor subtype-1, brain-derived neurotrophic factor, postsynaptic density-95, GABA-B receptor, and GABA-A receptor alpha-1) were significantly decreased (P < 0.05), suggesting a possible role for AnkG in cognition. It is possible that the loss of AnkG in the brain disrupts the excitation/inhibition balance of neurotransmitters, hindering the synaptic plasticity of neurons, and consequently leading to abnormal behavioral symptoms. Therefore, AnkG possibly contributes to neuroprotection and normal brain function, and may constitute a new target for treating neuropsychiatric diseases, especially cognitive dysfunction.

Cognitive flexibility: A trait of bipolar disorder that worsens with length of illness

INTRODUCTION

Deficits in cognitive flexibility, a difficulty altering thoughts and behavioral responses in a changing environment, are found in individuals with bipolar disorder (BD) and are associated with poor social and work functioning. However, the current literature is inconsistent in clarifying the long-term nature of these deficits for those with BD. We administered a common task of cognitive flexibility, the Wisconsin Card Sorting Task (WCST) and accounted for demographics, clinical, and cognitive features of BD, to determine the state versus trait characteristics of these deficits.

METHOD

The Wisconsin Card Sorting Test (WCST) was administered to 154 adults with BD and 95 healthy controls twice, one year apart.

RESULTS

The main findings show that cognitive inflexibility is a trait feature of BD, independent of clinical features, that may modestly worsen over time due to the presence of certain demographic, cognitive, and functional features of the disorder. In addition, improvements in WCST performance over an extended period of time in both those with and those without already existing cognitive flexibility deficits indicate potential practice effects.

CONCLUSIONS

These findings suggest that the implementation of early interventions before the illness progresses could potentially prevent further cognitive impairment, mitigate functional outcomes, and improve the quality of life of the individual with BD.

Executive dysfunction in bipolar disorder and borderline personality disorder

Objective

The boundary between bipolar disorder (BD) and borderline personality disorder is a controversial one. Despite the importance of the topic, few studies have directly compared these patient groups. The aim of the study was to compare the executive functioning profile of BD and BPD patients.

Method

Executive functioning (sustained attention, problem-solving, planning, strategy formation, cognitive flexibility and working memory) was assessed in BD (n= 30) and BPD outpatients (n= 32) using a computerized assessment battery (Cambridge Neuropsychological Test Automated Battery, CANTAB). The groups were compared to one another as well as to healthy controls.

Results

BD patients showed deficits in strategy formation and in planning (indicated by longer execution time in the ToL task) in comparison to BPD patients and healthy controls. BPD patients showed deficits in planning (short deliberation time in the ToL task) in comparison to BD patients and in comparison to healthy controls. In comparison to healthy controls, BPD patients displayed deficits in problem-solving.

Conclusions

Differences in executive dysfunction between BD and BPD patients suggest that this cognitive dimension may be relevant for the clarification of the boundary between the disorders.

The trajectory of neuropsychological dysfunctions in bipolar disorders: a critical examination of a hypothesis

OBJECTIVE

The hypothesis of a progressive nature of neuropsychological deficits in bipolar disorders is often accepted as an axiom by many clinicians and researchers in the field. However, contradictory pieces of data and a number of methodological concerns put it under debate.

METHOD

We reviewed findings from three different approaches to the study of the trajectory of cognitive features in bipolar disorders: longitudinal evaluation of cognition in affected subjects, cross-sectional neuropsychological assessment of patients belonging to different age groups, and exploration of the risk of dementia in bipolar subjects.

RESULTS

An increased risk of developing dementia was found in bipolar subjects. However, evidence from cross-sectional studies did not show more severe cognitive deficits in patients with longer illness duration. Furthermore, longitudinal studies revealed that bipolar subjects׳ cognitive performance did not change between different points in time.

CONCLUSIONS

After a thorough discussion of these findings and the limitations of the different approaches, we argue that, at present, there is no consistent evidence supporting that bipolar disorders, as a group, have a progressively deteriorating course of cognitive functions. Furthermore, we highlight the possible influence of psychotropic agents and metabolic factors on neuropsychological outcomes. Finally, we discuss the clinical implications of these findings and propose targets for forthcoming research.

A five-year follow-up study of neurocognitive functioning in bipolar disorder

OBJECTIVES

Cognitive dysfunction in bipolar disorder has been well-established in cross-sectional studies; however, there are few data regarding the longitudinal course of cognitive performance in bipolar disorder. The aim of this study was to examine the course of cognitive function in a sample of euthymic patients with bipolar disorder during a five-year follow-up period.

METHODS

Eighty euthymic outpatients with a DSM-IV diagnosis of bipolar disorder and 40 healthy control comparison subjects were neuropsychologically assessed at baseline (T1) and then at follow-up of five years (T2). A neurocognitive battery including the main cognitive domains of speed of processing, working memory, attention, verbal memory, visual memory, and executive function was used to evaluate cognitive performance.

RESULTS

Repeated-measures multivariate analyses showed that progression of cognitive dysfunction in patients was not different to that of control subjects in any of the six cognitive domains examined. Only a measure from the verbal memory domain, delayed free recall, worsened more in patients with bipolar disorder. Additionally, it was found that clinical course during the follow-up period did not influence the course of cognitive dysfunction.

CONCLUSIONS

Cognitive dysfunction that is characteristic of bipolar disorder is persistent and stable over time. Only dysfunction in verbal recall was found to show a progressive course that cannot be explained by clinical or treatment variables.

Neurocognitive impairments among youth with pediatric bipolar disorder: a systematic review of neuropsychological research

BACKGROUND

Pediatric bipolar disorder (PBD) has emerged as a field of research in which neuropsychological studies are continuously providing new empirical findings. Despite this, a comprehensive framework for neurocognitive impairments is still lacking, and most of the evidence remains unconnected. We addressed this question through a systematic review of neuropsychological research, with the aim of elucidating the main issues concerning this topic.

METHOD

A comprehensive search of databases (PubMed, PsycINFO) was performed. Published manuscripts between 1990 and January 2014 were identified. Overall, 124 studies fulfilled inclusion criteria. Methodological differences between studies required a descriptive review of findings.

RESULTS

Evidence indicates that verbal/visual-spatial memory, processing speed, working memory, and social cognition are neurocognitive domains impaired in PBD youth. Furthermore, these deficits are greater among those who suffer acute affective symptoms, PBD type I, and/or attention deficit hyperactivity disorder (ADHD) comorbidity. In addition, several neurocognitive deficits imply certain changes in prefrontal cortex activity and are somewhat associated with psychosocial and academic disabilities. Strikingly, these deficits are consistently similar to those encountered in ADHD as well as severe mood dysregulation (SMD). Besides, some neurocognitive impairments appear before the onset of the illness and tend to maintain stable across adolescence. Finally, any therapy has not yet demonstrated to be effective on diminishing these neurocognitive impairments.

LIMITATIONS

More prolonged follow-up studies aimed at delineating the course of treatment and the response to it are warranted.

CONCLUSIONS

Despite noteworthy research on the neurocognitive profile of PBD, our knowledge is still lagging behind evidence from adult counterparts.

The double burden of age and disease on cognition and quality of life in bipolar disorder

OBJECTIVE

Bipolar disorder (BPD) and normal aging are known to impact cognitive skills and health-related quality of life (HRQOL). This study investigated how aging and disease interact in predicting cognitive and psychosocial outcomes.

METHODS

Eight cognitive and ten subjective HRQOL domain ratings were measured. Subjects included 80 young (18-29 years) and late middle-aged (50-65 years) BPD patients in the euthymic phase and 70 age-equivalent healthy comparison participants.

RESULTS

An age X disease interaction was detected in three domains of cognitive functioning that reflect emotion processing, processing speed, and executive functioning skills, with BPD patients in the older group performing most poorly. There was a double burden of aging and disease on reported ability to perform physical tasks. However, regardless of age, disease status was associated with lower ratings of HRQOL in the psychosocial/affective sphere and the majority of cognitive domains. Post hoc analyses revealed that number of years ill was positively associated with select HRQOL ratings in older, but not younger BPD adults.

CONCLUSIONS

These findings may stimulate future longitudinal study of cognition and quality of life in BPD patients across the life span, focusing on additive and interactive effects of aging and disease burden, which could culminate in developing more effective treatment and rehabilitation strategies for this traditionally challenging to treat population.

Longitudinal course of cognitive deficits in bipolar disorder: a meta-analytic study

OBJECTIVE

Persistent cognitive deficits in bipolar disorder represent a major impediment to functional adjustment, but their static or progressive nature remains to be ascertained. The aim of this study was to synthesize findings from longitudinal research in order to examine the trajectory of cognitive impairment in bipolar disorder.

METHOD

A literature search was conducted through online databases covering the period between January 1990 and February 2014. Two approaches were undertaken. First, the results of longitudinal studies including neuropsychological assessment of stable bipolar patients at baseline and after a follow-up period of at least one year were meta-analyzed so as to obtain overall test-retest effect sizes for neurocognitive domains. Second, meta-analysis was restricted to longitudinal studies of bipolar patients including a control group. Patients' and controls' overall test-retest effect sizes were compared.

RESULTS

Bipolar patients' performance on 14 cognitive measures remained stable after a mean follow-up period of 4.62 years. When meta-analysis was restricted to controlled studies, no patient-control differences were found regarding longitudinal cognitive outcomes.

LIMITATIONS

Test-retest differences for medication variables and mood state could not be controlled. Sufficient data were not available to investigate a wider array of neuropsychological domains. Furthermore, most primary studies included relatively short test-restest intervals.

CONCLUSION

To date, the available evidence from longitudinal studies is not in accordance with the hypothesis of a progressive nature of cognitive deficits in BD. The implications of this finding for further research are discussed.