Abstract
BackgroundNearly all information processing during cognitive processing takes place during periods of sustained attention. Sustained attention deficit is among the most commonly reported impairments in bipolar disorder (BP). The majority of previous studies have only focused on bipolar I disorder (BP I), owing to underdiagnosis or misdiagnosis of bipolar II disorder (BP II). With the refinement of the bipolar spectrum paradigm, the goal of this study was to compare the sustained attention of interepisode patients with BP I to those with BP II.MethodsIn all, 51 interepisode BP patients (22 with BP I and 29 with BP II) and 20 healthy controls participated in this study. The severity of psychiatric symptoms was assessed by the 17-item Hamilton Depression Rating Scale and the Young Mania Rating Scale. All participants undertook Conners' Continuous Performance Test II (CPT-II) to evaluate sustained attention.ResultsAfter controlling for the severity of symptoms, age and years of education, BP I patients had a significantly longer reaction times (F(2,68) = 7.648, P = 0.001), worse detectability (d') values (F(2,68) = 6.313, P = 0.003) and more commission errors (F(2,68) = 6.182, P = 0.004) than BP II patients and healthy controls. BP II patients and controls scored significantly higher than BP I patients for d' (F = 6.313, P = 0.003). No significant difference was found among the three groups in omission errors and no significant correlations were observed between CPT-II performance and clinical characteristics in the three groups.ConclusionsThese findings suggested that impairments in sustained attention might be more representative of BP I than BP II after controlling for the severity of symptoms, age, years of education and reaction time on the attentional test. A longitudinal follow-up study design with a larger sample size might be needed to provide more information on chronological sustained attention deficit in BP patients, and to illustrate clearer differentiations between the three groups.
Highlights
The prevalence of bipolar disorder (BP) is estimated at 3.5% to 6.4% of the general population [1,2], and 30% to 50% of those in remission will not achieve premorbid psychosocial function levels [3]
No difference was observed between the two BP groups for illness duration, but severity of symptoms measured by Hamilton Depression Rating Scale (HDRS) and Young Mania Rating Scale (YMRS) were significantly higher in bipolar II disorder (BP II) than bipolar I disorder (BP I) (Table 1; HDRS: t = 36.91, P < 0.001; YMRS: t = 17.22, P < 0.001)
After using Pearson correlations to examine the relationships among all variables of sustained attention and clinical characteristics, no significant relationships were observed between Continuous Performance Test II (CPT-II) performance and clinical characteristics
Summary
The prevalence of bipolar disorder (BP) is estimated at 3.5% to 6.4% of the general population [1,2], and 30% to 50% of those in remission will not achieve premorbid psychosocial function levels [3]. Most previous studies only focused on type I bipolar disorder (BP I) with regard to neuropsychological aspects, mainly because type II bipolar disorder (BP II) was often underdiagnosed or misdiagnosed [5]. The distinctions between BP I and BP II have been reported in several studies, which indicate that BP I and BP II are in different diagnostic categories with regard to genetic [7,8], biological [9], clinical [10,11] and pharmacological [12] aspects. Sustained attention deficit is among the most commonly reported impairments in bipolar disorder (BP). With the refinement of the bipolar spectrum paradigm, the goal of this study was to compare the sustained attention of interepisode patients with BP I to those with BP II
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