Objectives: There are few longitudinal studies of neurocognition in bipolar disorder, and the short-term course of cognitive deficits in later-life bipolar disorder is unknown.
Methods: We administered a battery of neurocognitive tests, repeated 1-3 years after baseline, to 35 community-dwelling outpatients with bipolar disorder (mean age = 58), and compared their performance on a composite measure of cognitive functioning to that of demographically matched samples of normal comparison subjects (NCs; n = 35) and patients with schizophrenia (n = 35). Using regression analyses, we examined group differences in baseline performance, trajectory of change over time, and variability in performance across time. Within the bipolar group, we examined the impact of baseline severity and change in severity of psychiatric symptoms on intra-individual change in neurocognitive performance.
Results: At baseline, the group with bipolar disorder differed in overall neurocognitive functioning from the NCs, but did not differ significantly from the schizophrenia group. The bipolar group did not differ from the NCs or schizophrenia group in the mean trajectory of change between time-points, but the bipolar patients showed more intra-individual variability over time than the NCs or schizophrenia group. In the bipolar group, change in neurocognitive function was not related to baseline or change in psychiatric symptom severity.
Conclusions: Middle-aged and older community-dwelling adults with bipolar disorder have greater short-term variability in level of neurocognitive functioning relative to NCs or people with schizophrenia. The developmental course of and risk factors for cognitive deficits in bipolar disorder should be examined in future longitudinal studies.