Cognitive performance is impaired in euthymic Chinese patients with Bipolar 1 Disorder.

Background: Data from euthymic patients with Bipolar Disorder (BD) has shown cognitive impairment and the notion that sufferers of BD achieve full recovery between illness episodes is questionable. These findings have not been replicated in a Chinese population. The present study examined the cognitive profile of euthymic Chinese patients with Bipolar 1 Disorder (BD-1) and matched healthy control participants.

Methods: Euthymic patients with BD-1 and matched controls (n=104 in total) completed serial measures to assess mood and also completed an IQ test and the Central Nervous System Vital Signs (CNSVS) computerized battery assessing memory (verbal and visual), executive functions, attention, psychomotor and processing speed.

Results: Patients with BD-1 performed worse than controls on all cognitive domains. When using 2 or more scores below the 5th percentile as a cutoff for neurocognitive impairment, 46.2% of the patients with BD-1 and none of the control sample scored in this range (p<.001). Correlational analysis among the illness variables in BD-1 revealed that cognitive performance was inversely correlated with the number of manic episodes and duration of illness.

Limitations: It was not possible to determine the causal relationship between associated illness and performance. The effect of medication on cognitive performance requires further study.

Conclusions: Euthymic Chinese patients with BD-1 demonstrate marked cognitive impairments and these correlated with illness parameters. Cognitive impairment in BD may be independent of language and culture.