Cognitive impairment in euthymic older adults with bipolar disorder: a controlled study using cognitive screening tests

Background/objective: Cognitive impairment is a common feature of bipolar disorder (BD), with increased risk of developing dementia in late life. The aim of this study was to investigate the performance on cognitive screening tests in a sample of older adults with BD, as compared to non-BD subjects.

Methods: 186 older adults (86 with BD and 100 without BD) were included. Patients were stratified according to cognitive performance (normal cognition, mild impairment, and dementia). The comparison group comprised healthy controls; subjects with cognitive impairment but no dementia (CIND); or patients with probable or possible Alzheimer disease (AD). Sixty-five subjects were cognitively unimpaired (35 BD), 65 had CIND (25 BD), and 56 AD (26 BD). In each of these levels of cognitive function, we compared the performance of BD and non-BD subjects on the Mini-Mental State Examination (MMSE), verbal fluency test (VFT), and the Clock Drawing Test (CDT).

Results: Non-demented patients with BD had a slightly worse global cognitive performance as compared with healthy controls and patients with CIND, as shown by lower scores on the MMSE. Similarly, BD patients performed worse on the VFT, both in the normal cognition range and in the dementia range. Finally, demented BD patients had a significantly worse performance on the CDT as compared with patients with dementia due to AD.

Conclusion: Older adults with BD perform significantly worse on some cognitive screening tests as compared with those without BD across different levels of cognition.