Cognitive functioning in late life affective disorders: Comparing older adults with bipolar disorder, late life depression and healthy controls

Introduction: Both older age bipolar disorder (OABD) and late life depression (LLD) have been associated with cognitive dysfunction. It is unclear how cognitive functioning differs between these disorders and what the influence of current depressive symptoms is. Methods: We compared OABD (n = 148), LLD (n = 378) and healthy controls (HC) (n = 132) on cognitive functioning. Cognitive functioning was measured by an extensive neuropsychological assessment, and divided into four domains: episodic memory, processing speed, interference inhibition and working memory. Separate linear regression analyses were conducted with OABD as reference category, controlling for age, gender, level of education and severity of depressive symptoms. Results: Our findings show that OABD and LLD patients exhibit more cognitive dysfunction than HC, with OABD showing worst cognitive functioning on all cognitive domains, except for interference inhibition. These differences remained significant, even after controlling for the effect of depressive symptoms at the time of testing. Discussion: Our findings suggest that cognitive dysfunction in OABD is more severe in magnitude albeit in the same domains as in LLD. This difference cannot be fully explained by the severity of depressive symptoms. Future research should focus on other disease characteristics and how these characteristics are associated with the complex concept of cognitive functioning in both OABD and LLD.