Patients With Bipolar Disorder May Have Unique Age-Related Cognitive Decline

A cross-sectional study published in Psychological Medicine found evidence that cognitive domains are affected by aging differently among the bipolar disorder (BD) population.

Data for the cog-BD project were sourced from 4 different study cohorts recruited at the Centre for Addiction and Mental Health (CAMH) in Canada. Patients with BD (n=118) and controls (n=197) were assessed for cognitive function using the Hopkins Verbal Learning Test (HVLT-R), Continuous Performance Tests Identical Pairs (CPT-IP), Trail Making Test (TMT) parts A (TMT-A) and B (TMT-B), the Stroop Neuropsychological Screening Test (Stroop ratio), Neuropsychological Assessment Battery Mazes (mazes), Wechsler Memory Scale III Spatial Span (SS), and Brief Visuospatial Memory Test-Revised (BVMT-R) instruments. Cognitive functioning was compared between patients and controls on the basis of age.

The BD and control cohorts included individuals with a mean age of 42.41±19.87 and 36.57±17.98 years (P =.008), 61.9% and 51.8% were women, and they had received 14.90±2.15 and 15.49±2.00 years of education (P =.016), respectively. Stratified by age, 70 of the BD group and 153 of the controls had a mean age of 27.36 and 28.12 years, and 48 of the BD group and 44 of the controls had a mean age of 64.37 and 65.97 years, respectively.

The younger BD cohort differed from controls by HVLT-R scores (F, 3.62; P <.0001). The older BD cohort differed from controls by CPT-IP (F, 5.10; P <.001), TMT-A (F, 12.34; P <.001), SS (F, 10.35; P <.001), and Stroop ratio (F, 6.36; P <.001) scores.

Among patients with BD, the younger cohort had significantly higher CPT-IP (P <.001), SS (P <.001), BVMT-R (P =.001), and mazes (P <.001) scores and significantly lower TMT-A (P <.001), TMT-B (P <.001), and Stroop ratio (P <.001) scores compared with the older patients.

In general, the investigators observed a pattern of accelerated cognitive aging among the BD cohorts, in which patients had steeper decreases in cognitive performance with age compared with controls. Conversely, visual special memory and reasoning did not appear to be differentially affected by age in BD. For verbal memory, patients with BD exhibited early impairment but had similar age-related declines as were observed with normal aging.

These findings may not be generalizable for patients with BD who are not receiving pharmacological management.

Study authors concluded, “Our study supports the concept of accelerated aging in BD for the domains of attention/vigilance, processing speed, and executive function/working memory. It also supports the concept of an early impairment associated with some (unspecified) neurodevelopmental process for verbal memory, and declines due to normal aging for the domains of reasoning/problem solving and visuospatial memory. Both larger cross-sectional studies and longitudinal studies are needed to explore trajectories of cognitive domain performance in BD.”