Does cognitive function in older bipolar patients depend on recurrent or current mood symptoms?

Background: Cognitive impairment in patients with bipolar disorder (BD) is viewed as an integral part of the disorder that seems to be rather stable and even present in euthymic state. Current mood symptoms influence cognition negatively and multiple mood episodes could lead to more severe psychopathology and cognitive impairment, resulting in a hypothesized neuroprogressive course of BD. The influence of current mood symptoms and recurrent mood episodes on cognitive functioning warrants further exploration. Methods: Cohort 1 included 20 hypomanic and 21 depressed older adults with bipolar disorder (OABD) of which 20 were reassessed in the euthymic state and 50 healthy subjects. Cohort 2 included 27 OABD who had no recurrent mood episodes during 5 years and 29 who had recurrent mood episodes during 5 years. Neuropsychological examination including tests for memory, executive function, attention and verbal fluency was performed repeatedly in all subjects. Results: In cohort 1 cross-sectional analyses showed that hypomanic, depressed and euthymic patients groups did not differ from each other with respect to their cognitive functioning, except for attention, which was poorer only in depressed patients. Regardless of mood state patients experienced significantly worse cognitive functioning compared to the healthy subjects. Within subject comparisons revealed that performance on memory tasks was worse in patients with current mood symptoms; depressed patients were more impaired in the learning condition and hypomanic patients were more impaired in delayed recall. In cohort 2 cognitive functioning was not different in patients with or without recurrence in 5 year follow-up. Conclusions: Although OABD had worse cognitive functioning than healthy subjects, there was a quite stable pattern of cognitive impairment, regardless of current or recurrent mood episodes. These results do not provide consistent support for the hypothesis of neuroprogression in BD.