Older patients with bipolar disorder and clinical depression show greater cognitive changes—and a greater medical burden—than their peers.
SAVANNAH, GA—Cognitive deficits are greater in elderly patients with bipolar disorder and major depressive disorder (MDD) than in healthy controls, according to research presented at the 2010 Annual Meeting of the American Association for Geriatric Psychiatry.
Researchers from the Geriatric Psychiatry Mood Disorders Research Program at McLean Hospital, in Belmont, Massachusetts, examined neurocognitive function and its associated medical burden in 97 older adults (mean age, 68.9) with bipolar disorder and MDD compared with control subjects. The subjects and controls covered a broad spectrum of demographics, including sex (48.5% female), age of disease onset, education levels, and IQ.
Participants were given cognitive assessments, including the Stroop test, Trails A and B, Mini Mental-State Examination (MMSE), Consortium to Establish a Registry for Alzheimer’s Disease (CERAD), Wechsler Abbreviated Scale of Intelligence (WASI), Global Assessment of Functioning (GAF), Montgomery-Åsberg Depression Rating Scale (MADRS), and Cumulative Illness Rating Score for Geriatrics (CIRS-G).
The investigators compared the demographic and clinical characteristics of the sample, and used linear regression and Fisher’s exact test to compare neuropsychological test scores among the three groups. The researchers then used linear regression models with CIRS-G total score, diagnosis, and CIRS-G total score by diagnosis interaction, age, sex, and education as study covariates.
For each neuropsychological outcome and GAF, the investigators tested for an association with CIRS-G total score separately for each group and for a difference in the association among diagnostic groups, and a Bonferroni correction was applied as applicable to account for repeat testing.
“Older adults with major depressive disorder (MDD) or bipolar disorder (BP) have been shown to demonstrate cognitive deficits in multiple domains, including memory, attention, executive functioning, and processing speed,” Brittany L. Jordan, BA, of the Geriatric Research Program at McLean Hospital, and colleagues wrote. “Additionally, individuals with MDD or bipolar disorder have greater medical comorbidity than the general population … [which] has been linked to poorer treatment outcomes in MDD or bipolar disorder as well as poorer cognitive functioning.”
A Higher Medical Burden
On measures of executive functioning, processing speed, verbal fluency, and verbal memory, controls performed significantly better than MDD or bipolar diagnostic groups. Researchers found no significant relationship by diagnostic group for the Stroop Word, CERAD trial 1, or MMSE measures. Patients with diagnoses of depression or bipolar disorder had significantly higher CIRS-G total scores than controls on the linear regression model of CIRS-G total score with the outcome and diagnosis, age, sex, and education as study predictors. They also reported a significant association between diagnosis and CIRS-G vascular score using ordinal logistic regression, with odds for higher scores in both patient groups compared to controls.
“Both subject groups exhibited significantly greater medical burden than controls,” the researchers explained. “Both subject groups performed significantly worse than controls on most measures of neuropsychological functioning, intelligence, and global functioning, but the subject groups did not differ from each other.”
In addition, the researchers noted that CIRS-G scores did not significantly predict neuropsychological outcomes in most cases, suggesting that these deficits are not secondary to medical burden.
“These findings indicate that older adults with bipolar disorder or MDD have greater medical burden than elderly participants without psychiatric illness. Additionally, the present finding of an association between cognitive deficits and bipolar disorder or MDD is consistent with models in which neuropsychological deficits represent a core feature of bipolar disorder or MDD in older adults without a diagnosis of dementia, rather than simply a consequence of greater medical burden in these individuals,” Ms. Jordan’s group wrote. “Associations among neurocognitive functioning, medical burden, and affective illness in elderly populations have important implications for functional outcomes in geriatric patients with mood disorders. As mood disorders and medical comorbidities are associated with cognitive deficits and poor functional outcomes, a more integrative treatment model may enhance the effectiveness of clinical interventions with these individuals.”
Neurocognitive Deficits
A second study presented at the conference examined neuropsychological, clinical, and community function in a small sample of geriatric patients with MDD or bipolar disorder and found that neurocognitive functioning in patients was significantly poorer than in a healthy comparison group. Eighteen study patients were given a series of neurocognitive and clinical tests, including the MMSE, Stroop, Trails A and B, Wisconsin Card Sorting Test, Verbal Fluency, and CERAD, at baseline and again approximately one year later.
Kathryn E. Lewandowski, PhD, of the Schizophrenia and Bipolar Disorder Program at McLean Hospital, and colleagues used the Wilcoxon signed-rank test and Fisher’s exact test to compare demographic, clinical, and neuropsychological characteristics between MDD and bipolar subjects at baseline, and compared scores between baseline and follow-up using the Wilcoxon test.