Cognitive decline not apparent in bipolar patients

By Laura Cowen, medwireNews Reporter

Cognitive dysfunction is persistent but generally stable over time in patients with bipolar disorder, Spanish researchers report.

“Only dysfunction in verbal recall may show a progressive course that cannot be explained by clinical or pharmacological factors”, write Eva María Sánchez-Morla (Hospital Universitario de Guadalajara, Spain) and colleagues in Bipolar Disorders.

The researchers conducted 11 cognitive tests to assess speed of processing, working memory, attention, verbal memory, visual memory and executive function at baseline and 5 years later in 80 euthymic outpatients with bipolar disorder (mean age 44.4 years) and 40 mentally healthy controls (mean age 44.8 years).

Patients with bipolar disorder recorded lower scores than controls in all cognitive domains at both time points.

However, the change in speed of processing, working memory, attention, visual memory and executive function during the course of the study did not differ between patients and controls. Both groups showed significant improvements in working memory and the verbal fluency aspect of executive function, while the remaining cognitive variables remained stable over time.

Only delayed free recall, a measure of verbal memory, worsened significantly for patients, but not for controls, during the study. And significance remained after accounting for the number of psychopharmacological agents, lithium levels and antipsychotic dose. There was no decline, however, in the other measures of verbal memory (learning, immediate free recall and recognition).

Between baseline and follow-up, 69.4% of patients had at least one affective episode and 35.0% had at least one psychiatric admission.

Over half (59.7%) were classified as having a good clinical outcome, defined as no more than two major affective episodes during follow-up and recovery within 12 weeks of starting treatment. But there was no difference in the course of cognitive dysfunction between these patients and the 40.3% with poor clinical outcome.

“Our study indicates that the cognitive deficit observed in our sample of patients with bipolar disorder is stable, both in those with a good and in those with a poor clinical outcome”, Sánchez-Morla et al remark.

They add that their findings “are generally in agreement with previous studies indicating that cognitive dysfunction in midlife patients with bipolar disorder is not progressive.”

But the team concludes that, “in agreement with previous literature, the possibility cannot be excluded that older patients with bipolar disorder exhibit greater impairment in cognitive function over time than control healthy comparators.”

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