The longitudinal course of cognition in older adults with bipolar disorder

Autor: Charles F. Reynolds, Benoit H. Mulsant, Adriana V Hyams, Sati Mazumdar, Meryl A. Butters, Ariel G. Gildengers, David J. Kupfer, Amy E. Begley
Rok vydání: 2009
Předmět:
Zdroj: Bipolar disorders. 11(7)
ISSN: 1399-5618
Popis: More than 30 cross-sectional studies have revealed cognitive impairments in mixed-aged adults with bipolar disorder (BD) that are present even with symptomatic recovery (1–4). Deficits have been identified in multiple cognitive domains, including information processing speed (5, 6), executive function (5–10), memory (7, 11–14), attention/concentration (15, 16), and visual-spatial abilities (17, 18). In turn, cognitive impairment has been associated with impairment in functional abilities (5, 6, 13). Epidemiologic studies have suggested that BD is associated with increased risk of developing dementia (19–21). Despite the large number of cross-sectional studies, to our knowledge, there have been just six published studies on the longitudinal course of cognitive function in BD patients of any age (22–27), with only one study focused on older adults (23). This study by Dhingra and Rabins (23) used the Mini-Mental State Exam (MMSE) (28) to follow older patients for 5–7 years after they were hospitalized for mania. The investigators found that 8 (32%) of the 25 BD subjects followed-up experienced a decline in their MMSE to a score below 24 (indicating significant cognitive impairment), including 5 subjects (20%) who became so cognitively impaired that they required nursing home placement. Although no control group was included, this is ten-fold higher than the 1–2% expected incidence rate of dementia, given the age of these patients. Furthermore, the MMSE may have underestimated the level of cognitive dysfunction present in their subjects, since the instrument has low sensitivity to detect cognitive impairment in older adults with mood disorders (29). More recently, Depp and colleagues (26) examined the ‘short-term’ course of neuropsychological abilities in middle-aged and older adults with BD. They examined 35 community-dwelling outpatients with BD (mean age 58 years) with a battery of neurocognitive tests, repeated once (1–3 years after baseline), comparing the performance with that of demographically matched samples of normal comparison subjects (n = 35) and patients with schizophrenia (n = 35). They found that patients with BD did not differ from normal comparators or patients with schizophrenia in the mean trajectory of change between time-points, but that the patients with BD showed more intra-individual variability over time than either comparison group. In their study, although subjects with BD or schizophrenia had mild/minimal levels of psychopathology, they were not specifically tested when stable or symptom-free. The reports from middle-aged adults with BD present a mixed picture of stability or decline of cognition over longitudinal follow-up (22, 24, 25, 27). The reports from Engelsmann et al. (24) and Balanza-Martinez et al. (22) in midlife subjects showed that impairments in cognitive function were present in memory (24) or overall cognitive function (22); however, no significant decline was evident over the three to six years of follow-up. When assessed in euthymic states, Mur and colleagues (27) observed stable cognitive deficits in executive function and information processing speed over two-year follow-up in patients treated with lithium as their primary mood stabilizer. In contrast, in Moorhead et al.’s study (25), 20 patients with bipolar I disorder (BD I) (mean age: 42 ± 9) and 21 controls (group-matched for age, gender, and premorbid IQ) underwent cognitive assessment and had MRI brain scans at baseline and four years later. Patients with BD showed a larger decline in hippocampal, fusiform, and cerebellar gray matter density over four years than control subjects. Reductions in temporal lobe gray matter correlated with decline in cognitive function (verbal IQ) and number of mood episodes during the follow-up period. Taken together, the reports from middle or older age suggest that cognitive impairments may manifest in early life, but significant decline may not be apparent until late middle or older age. Not surprisingly, cognitive function is strongly associated with performance of ‘cognitive’ instrumental activities of daily living (IADLs) (e.g., medication management, managing finances, or home safety) and the ability to live independently (6). Determining whether elders with BD genuinely exhibit accelerated cognitive decline is critical for investigators to design or optimize treatments targeting specific factors or subgroups of patients with BD. For instance, patients with BD who exhibit a specific pattern of cognitive impairment or a cluster of risk factors indicating a very high risk of further cognitive decline may be candidates for cognitive remediation or interventions designed to enhance cognitive function or halt decline. To clarify whether cognitive decline is ‘accelerated’ in older adults with BD, we have assessed a group of patients with BD over several years with the Dementia Rating Scale (DRS) (30), along with a group of age-equated, mentally healthy comparators. We decided to include both BD I and bipolar II disorder (BD II) in our investigation to describe the cognitive course of BD in older adults that may generalize to individuals in the community. Based on our prior research in bipolar and major depressive disorders (6, 31, 32), we hypothesized that subjects with BD would exhibit cognitive deficits in relation to age-matched, mentally healthy comparators and that they would exhibit faster decline over longitudinal follow-up. We secondarily examined whether the profile of cognitive function across the DRS subscales revealed greater levels of impairment or decline in attention, executive function, or memory in patients with BD.
Databáze: OpenAIRE
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