Review articlePrevalence and correlates of cognitive impairment in euthymic adults with bipolar disorder: A systematic review
Introduction
Bipolar disorder (BD) is known to be associated with cognitive impairment, which persists between illness episodes and contributes to functional disability. Impairment is typically found on tests of attention, working and episodic memory, processing speed and executive function, with significant group differences of medium to large effect size compared to healthy comparison groups (Arts et al., 2008, Bourne et al., 2013, Mann-Wrobel et al., 2011, Robinson et al., 2006). Although such group-level differences have been consistently reported, the proportion of adults with BD who have clinically relevant levels of cognitive impairment has not yet been clearly established. It is likely that there is marked within-group variation, ranging from normal performance through to severe multi-domain impairment. It has been argued that if overall group differences are being driven by a subgroup of patients with marked levels of impairment, this serves to obscure the true picture of cognitive impairment in the BD population, which in fact may be severe for some and absent for many others (Iverson et al., 2011).
There are a number of reasons why it would be beneficial to establish the prevalence of cognitive impairment in the BD population. From a clinical point of view, cognitive impairment is a major contributor to the overall burden of disability in mood disorders, and is a target in its own right for therapeutic intervention. Service planning would be helped by clearer information about numbers and characteristics of those who are likely to need more clinical or social care input to manage the disabling effects of cognitive impairment. From a research perspective, shifting our focus to identifying subgroups with cognitive impairment will facilitate efforts to understand why some people with BD experience significant problems with cognition while others remain unimpaired. This, in turn, may help to identify particular risk factors for clinically significant cognitive impairment.
- 1.
To determine the prevalence of cognitive impairment in euthymic adults with a history of BD.
- 2.
To describe sociodemographic, clinical and other factors that are associated with cognitive impairment in BD.
The population of interest was community-dwelling adults with a history of BD (the exposure), who were euthymic at the time of assessment. The outcome of interest was cognitive impairment, measured using standardised tests; presence or absence of impairment was defined with reference to healthy population norms. Since the aim was to determine prevalence, only cross-sectional results were considered (cross-sectional studies or baseline results from cohort studies or trials).
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Materials and methods
The review was conducted according to a structured protocol which followed PRISMA-P guidance (Moher et al., 2015). The protocol was registered on the PROSPERO database on 16 March 2015 (reference number CRD42015017558; http://www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42015017558). Reporting is in accordance with PRISMA and MOOSE guidelines (Moher et al., 2009, Stroup et al., 2000).
Article selection
Fig. 1 shows a PRISMA flow diagram of the article selection process. Titles and/or abstracts of 5412 records were screened for eligibility, followed by full text evaluation of 658 papers. Forty-six articles were deemed eligible. The most common reasons for exclusion were lack of evidence of consecutive sample recruitment, inclusion of in-patients in study samples, and inclusion of non-euthymic participants. Examples of acceptable sample recruitment methods in the eligible articles were
Summary of findings
The aims of this review were to determine the prevalence of cognitive impairment in euthymic adults with BD, and to ascertain which clinical, sociodemographic or other factors were associated with cognitive impairment in this population. Thirty articles contributed to the findings, of which 15 provided prevalence. Impairment prevalence was similar between BD-I only and mixed BD samples. One study with separate results for BD-I and BD-II participants indicated that impairment was more common in
References (43)
- et al.
Neurocognitive function in clinically stable men with bipolar I disorder or schizophrenia and normal control subjects
Biol. Psychiatry
(2004) - et al.
Theory of mind and functionality in bipolar patients with symptomatic remission
Rev. Psiquiatr.Salud Ment.
(2013) - et al.
Is processing speed a valid cognitive endophenotype for bipolar disorder?
J. Affect. Disord.
(2012) - et al.
Cognitive functions among euthymic bipolar I patients after a single manic episode versus recurrent episodes
J. Affect. Disord.
(2011) - et al.
Cognitive functions and cognitive styles in young euthymic patients with bipolar I disorder
J. Affect. Disord.
(2013) - et al.
The Maudsley Bipolar Disorder Project: Executive dysfunction in bipolar disorder I and its clinical correlates
Biol. Psychiatry
(2005) - et al.
Identifying a cognitive impairment subgroup in adults with mood disorders
J. Affect. Disord.
(2011) - et al.
What is the contribution of executive dysfunction to the cognitive profile of bipolar disorder? A well-controlled direct comparison study
Rev. Colomb. Psiquiatr.
(2011) - et al.
Heterogeneity in cognitive functioning among patients with bipolar disorder
J. Affect. Disord.
(2008) - et al.
Theory of mind and facial emotion recognition in euthymic bipolar I and bipolar II disorders
Psychiatry Res.
(2011)
Toward the identification of neurocognitive subtypes in euthymic patients with bipolar disorder
J. Affect. Disord.
Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement
J. Clin. Epidemiol.
Spatial working memory function in twins with schizophrenia and bipolar disorder
Biol. Psychiatry
A meta-analysis of cognitive deficits in euthymic patients with bipolar disorder
J. Affect. Disord.
Comparative study of neurocognitive function in euthymic bipolar patients and stabilized schizophrenic patients
Psychiatry Res.
A comparison of euthymic bipolar patients with unaffected first-degree relatives and healthy controls in terms of neuropsychological functions
Int. J. Psychiatry Clin. Pract.
Meta-analyses of cognitive functioning in euthymic bipolar patients and their first-degree relatives
Psychol. Med.
Neuropsychological testing of cognitive impairment in euthymic bipolar disorder: an individual patient data meta-analysis
Acta Psychiatr. Scand.
Case-control study of neurocognitive function in euthymic patients with bipolar disorder: an association with mania
Br. J. Psychiatry
Cognitive performance is impaired in euthymic Chinese patients with Bipolar 1 Disorder
J. Affect. Disord.
Levels of TNF-, soluble TNF receptors (sTNFR1, sTNFR2), and cognition in bipolar disorder
Hum. Psychopharmacol. Clin. Exp.
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