Prefrontal and paralimbic metabolic dysregulation related to sustained attention in euthymic older adults with bipolar disorder.

OBJECTIVE: Reports of sustained attention deficits in the euthymic phase of bipolar disorder have been variable, and have yet to be related to cerebral metabolism. In the present study, we evaluated relationships between cognitive performance deficits and resting cerebral metabolism in euthymic older adults with bipolar disorder. METHODS: Sixteen older (mean age 58.7 years) euthymic outpatients with bipolar disorder (10 type I, 6 type II; 44% female) and 11 age-matched healthy controls received resting positron emission tomography with (18) fluorodeoxyglucose and, within 10 days, the Conners' Continuous Performance Test-II, a commonly used measure of sustained attention and inhibitory control. RESULTS: Bipolar disorder patients had significantly more omission errors (z = 2.53, p = 0.01) and a trend toward more commission errors (z = 1.83, p < 0.07) than healthy controls. Relative to healthy controls, among bipolar disorder subjects commission errors were more strongly related to inferior frontal gyrus [Brodmann area (BA) 45/47] hypometabolism and paralimbic hypermetabolism. In bipolar disorder subjects, relative to controls, omission errors were more strongly related to dorsolateral prefrontal (BA 9/10) hypometabolism and greater paralimbic, insula, and cingulate hypermetabolism. CONCLUSIONS: In older adults with bipolar disorder, even during euthymia, resting-state corticolimbic dysregulation was related to sustained attention deficits and inhibitory control, which could reflect the cumulative impact of repeated affective episodes upon cerebral metabolism and neurocognitive performance. The relative contributions of aging and recurrent affective episodes to these differences in bipolar disorder patients remain to be established.

Corticolimbic metabolic dysregulation in euthymic older adults with bipolar disorder.

The corticolimbic dysregulation hypothesis of bipolar disorder suggests that depressive symptoms are related to dysregulation of components of an anterior paralimbic network (anterior cingulate, anterior temporal cortex, dorsolateral prefrontal cortex, parahippocampal gyrus, and amygdala) with excessive anterior limbic activity accompanied by diminished prefrontal activity. In younger patients, such abnormalities tend to resolve with remission of depression, but it remains to be established whether the same is true for older patients. This was a cross-sectional, between-subjects design conducted with 16 euthymic, medicated patients with bipolar disorder (10 type I, six type II) and 11 age-matched healthy controls. All participants were over age 50. Our main outcome measures were relative rates of cerebral metabolism derived from a resting (18)flourodeoxyglucose positron emission tomography scan in specified regions of interest in the corticolimbic network. Resting metabolic rates in bipolar patients were significantly greater than in controls in bilateral amygdalae, bilateral parahippocampal gyri, and right anterior temporal cortex (BA 20, 38); they were significantly lower in bipolar patients than in controls in the bilateral dorsolateral prefrontal cortices (BA 9, 10, 46). The evidence of corticolimbic dysregulation observed is consistent with the hypothesis that bipolar disorder entails progressive, pernicious neurobiological disruptions that may eventually persist during euthymia. Persistent corticolimbic dysregulation may be related to residual affective, behavioral, and cognitive symptoms in older patients with bipolar disorder, even when not experiencing syndromal mood disturbance.

Resting prefrontal hypometabolism and paralimbic hypermetabolism related to verbal recall deficits in euthymic older adults with bipolar disorder.

OBJECTIVES: To evaluate deficits of delayed free recall in euthymic older patients with bipolar disorder and relate deficits to resting cerebral metabolism. DESIGN: Two group, between subjects. SETTING: Outpatient. PARTICIPANTS: Participants included 16 older adult (mean age, 58.7 years; SD = 7.5) euthymic outpatients with bipolar disorder (10 Type I and 6 Type II) and 11 healthy comparison subjects (mean age, 58.3 years; SD = 5.2). MEASUREMENTS: All participants received resting positron emission tomography with (18)flurodeoxyglucose and, within 10 days, delayed free verbal recall testing with the California Verbal Learning Test II. RESULTS: Patients with bipolar disorder, relative to healthy comparison subjects, had significantly poorer delayed free verbal recall. In patients with bipolar disorder, relative to healthy comparison subjects, prefrontal hypometabolism (dorsolateral prefrontal cortex) and paralimbic hypermetabolism (hippocampus, parahippocampal gyrus, and superior temporal gyrus) was associated with recall deficits in patients with bipolar disorder. Prefrontal and limbic metabolism were inversely related. CONCLUSION: Our findings demonstrate an association between prefrontal hypometabolism and paralimbic hypermetabolism and verbal memory deficits in euthymic older patients with bipolar disorder. Verbal memory deficits may be a clinical consequence of corticolimbic dysregulation in bipolar disorder, even during euthymia. This suggests that such dysregulation and related deficits could be bipolar disorder traits.

Substance use disorders as risk factors for psychiatric hospitalization in bipolar disorder.

OBJECTIVE: This study developed risk profiles of psychiatric hospitalization for veterans diagnosed as having bipolar disorder. METHODS: This study included 2,963 veterans diagnosed as having bipolar disorder (types I, II, or not otherwise specified) during the 2004 fiscal year. Data were derived from the Veterans Affairs administrative database. Risk profiles for psychiatric hospitalization were generated with an iterative application of the receiver operating characteristic. RESULTS: In this sample 20% of the patients with bipolar disorder were hospitalized psychiatrically during the one-year study period. Patients diagnosed as having both an alcohol use disorder and polysubstance dependence and who also were separated from their spouse or partner had a 100% risk of psychiatric hospitalization; risk of psychiatric hospitalization decreased to 52% if the patients were not separated from their partner. Patients who were not diagnosed as having alcohol use disorders or polysubstance dependence and who were not separated from their partners exhibited the lowest risk of psychiatric hospitalization (12%). Among patients with a psychiatric hospitalization, 41% had longer lengths of stay (<14 days), with the strongest predictor of a longer length of stay being an age older than 77 years, which conferred a 77% risk. CONCLUSIONS: Alcohol use and polysubstance dependence can significantly affect the course of bipolar disorder, as evidenced by their associations with psychiatric hospitalizations. Increased focus on substance abuse among older adults with bipolar disorder may decrease length of psychiatric hospitalization. Our findings suggest that implementing substance treatment programs early in the course of bipolar disorder could reduce health service use.