Late-life depression and increased risk of dementia: a longitudinal cohort study.

Late-life depression (LLD) is associated with an increased risk of developing dementia; however, it is not known whether individuals with a history of LLD exhibit a more rapid rate of cognitive decline. We aimed to determine whether those with LLD experienced faster cognitive decline compared with never-depressed control (NDC) participants from the community and whether stratification of LLD into early-onset depression (EOD) and late-onset depression (LOD) subtypes revealed differing rates and domain-specific expression of cognitive decline. We conducted a prospective, longitudinal study where 185 participants with LLD (remitted) and 114 NDC were followed for 5 years on average. EOD was defined as having first lifetime depressive episode at <60years and LOD at ≥60years. Every year, participants underwent comprehensive neuropsychological assessment. Composite scores for each cognitive domain were calculated through averaging standardized scores across tests. LLD compared to NDC demonstrated significant baseline impairment but did not decline more rapidly. EOD were significantly impaired in attention/processing speed and global cognitive function at baseline but did not experience more rapid decline as compared to NDC. Those with LOD compared to both NDC and EOD performed worse in all domains at baseline and experienced more rapid decline in verbal skills and delayed memory ability. Our findings suggest that baseline impairment may lower the threshold for those with LLD to develop dementia. EOD and LOD may represent distinct phenotypes of cognitive impairment with differing neural substrates. LOD may represent a distinct phenotype with a more rapid decline in verbal skills and delayed memory.

Endogenous concentrations of DHEA and DHEA-S decrease with remission of depression in older adults.

BACKGROUND: Clinical studies of endogenous concentrations of dehydroepiandrosterone (DHEA) and its sulfated conjugate DHEA-S in depression are limited. This study was designed to evaluate the influence of successful pharmacological treatment of late-life depression on concentrations of DHEA, DHEA-S and cortisol. METHODS: We determined endogenous concentrations of DHEA, DHEA-S and cortisol in elderly control subjects (n = 16) and in elderly depressed patients who remitted (n = 44) or failed to remit (n = 16) with pharmacological treatment. Depressed patients were treated for 12 weeks with either nortriptyline or paroxetine. RESULTS: In remitters, DHEA and DHEA-S concentrations were lower at week 12 than at week 0 (p =.002 and p =.0001, respectively). In the nonremitters and control subjects, neither DHEA nor DHEA-S concentrations changed. Decreases in hormone concentrations were associated with improvement in mood and functioning in depressed patients. Although cortisol concentrations decreased in remitters and nonremitters, the change was not significant. CONCLUSIONS: Our data suggest that the decrease in DHEA and DHEA-S in remitters is related to remission of depression rather than to a direct drug effect on steroids, as nonremitters had no change in hormone concentrations.

Dual-task performance in depressed geriatric patients.

Older patients suffering from a major depression are often impaired on tasks that require executive control processes. However, a wide variety of executive abilities exist in humans, and it is not clear that all are impaired in depression or that such impairments persist beyond remission of the depression. One executive process that plays a central role in mental operations such as working memory is the ability to co-ordinate the simultaneous performance of multiple tasks. Dual-task performance has been extensively studied in normal subjects but there is little work with depressed patients. The present study examined the performance of depressed (M age=71.0, S.D.=7.1) and control subjects (M age=69.3, S.D.=7.0) on two tasks (visual tracking and backward digit span), both when each task was carried out by itself and when the two tasks were carried out simultaneously. Dual-task performance was impaired in depressed patients prior to antidepressant treatment and this impairment persisted even after remission of the depression. These results suggest that, like other executive abilities, the ability to schedule and co-ordinate the conflicting processing demands present in a dual-task situation is impaired in depressed geriatric patients and that this impairment may be a trait effect.

Changes in cognitive functioning following treatment of late-life depression.

OBJECTIVE: Knowledge of the relationship between various clinical characteristics and cognitive functioning is advancing, but little is known about the cognitive response to treatment for geriatric depression. The purpose of this study was to examine the cognitive response to treatment for patients with late-life depression. METHOD: Subjects included 45 nondemented, elderly depressed patients who achieved remission after 12 weeks of antidepressant treatment and 20 elderly comparison subjects. All subjects were administered a battery of clinical measures, including cognitive screening instruments, before and after treatment. RESULTS: As a group, the elderly depressed patients showed a small improvement in overall cognitive functioning after treatment. Among depressed patients with concomitant cognitive impairment at baseline, performance on the Mattis Dementia Rating Scale domains of conceptualization and initiation/perseveration improved significantly relative to those of depressed patients with normal cognition. Despite the improvement following treatment, the overall level of cognitive functioning in the elderly depressed patients with cognitive impairment at baseline remained mildly impaired, especially in the memory and initiation/perseveration domains. CONCLUSIONS: Elderly depressed patients with cognitive impairment may experience improvement in specific domains following antidepressant treatment but may not necessarily reach normal levels of performance, particularly in memory and executive functions. This subgroup of late-life depression patients is likely at high risk of developing progressive dementia.

Decreased working memory and processing speed mediate cognitive impairment in geriatric depression.

BACKGROUND: While neuropsychological dysfunction is common in geriatric depression, not all aspects of cognition are equally affected. It has been suggested that depressed patients are impaired only in tasks that make heavy demands on processing resources and that a resource decrement therefore underlies the neuropsychological decrements seen in geriatric depression. The present study examined whether processing resources in the form of working memory and information processing speed are decreased in depression and whether a decrease in these resources actually mediates neuropsychological impairment. METHODS: Measures of processing resources were administered to elderly depressed patients prior to treatment and to age-matched controls. Patients whose depression remitted were retested as were the controls. Subjects also received neuropsychological tests of episodic memory and visuospatial performance. RESULTS: Depressed patients performed significantly worse on measures of both processing speed and working memory. While performance on these measures improved in patients whose depression remitted, the amount of improvement was no greater than that seen in the controls with repeat testing. Hierarchical regression analyses showed that depression explained a significant amount of variance on the neuropsychological tasks. However, if the variance associated with processing resources was removed first, depression no longer accounted for a significant amount of neuropsychological variance. CONCLUSIONS: Processing resources are decreased in elderly depressed patients and this decrease in resources appears to mediate impairments in several areas of neuropsychological functioning including episodic memory and visuospatial performance. The resource decrement persists after remission of the depression and thus may be a trait marker of geriatric depression.

Cognitive effects of paroxetine in older depressed patients.

This study examined whether paroxetine produces cognitive toxicity in elderly patients suffering from a major depressive episode. Twenty-nine depressed patients with a wide range of cognitive functioning were treated with paroxetine. At baseline and during 6 weeks of treatment, patients were asked to complete various measures of cognitive function and had blood drawn to determine serum anticholinergicity. Measures of attention and cognitive speed showed significant improvement with treatment, while the memory performance remained unchanged. A similar pattern of results was found in both cognitively impaired and intact patients. The slight increase in serum anticholinergicity seen in some elderly patients did not significantly impair cognitive function, even in patients with a preexisting cognitive impairment.