Physical multimorbidity is not independently associated with cognitive performance in patients with older-age bipolar disorder (OABD)

Objectives: Cognitive impairment is common in bipolar disorder (BD), especially in older age (≥50 years). Underlying causes of BD-related cognitive impairment are not fully elucidated. This study investigates the association between physical multimorbidity and subjective and objective cognitive performance in patients with older age bipolar disorder (OABD). Design: Cross-sectional design. Setting: Dutch Older Bipolars (DOBi) dynamic cohort. Participants: 170 outpatients with BD aged ≥ 50 years. Measurements: Chronic physical diseases were assessed in a structured interview. Objective cognitive performance was measured with neuropsychological tests, subjective cognitive performance with the Cognitive Failures Questionnaire (CFQ). Linear regression analyses were performed between multimorbidity, defined as two or more affected physical disease domains, and 1) objective cognitive performance, 2) subjective cognitive functioning, and 3) four cognitive domain scores (attention, learning and memory, verbal fluency, executive functioning). Analyses were hierarchically adjusted for demographic, lifestyle, and psychiatric characteristics. Results: Multimorbidity was significantly associated with a lower composite cognitive score (B=−0.205, p = 0.040), but after full adjustment statistical significance disappeared (B=−0.044, p = 0.633). Controlled for demographics only, multimorbidity was not significantly associated with higher CFQ (B=6.009, p = 0.053). Multimorbidity was associated with worse executive functioning (B=−0.279, p = 0.018), but statistical significance disappeared after full adjustment (B=−0.085, p = 0.469). Conclusions: In OABD physical multimorbidity is not independently associated with poorer cognitive performance and subjective functioning. Rather, shared risk factors, such as demographics, psychiatric characteristics, and lifestyle factors might lead to both the presence of physical diseases and worse cognitive performance in OABD.