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Very old age has moved in recent years from the status of an anecdotal phenomenon to a significant concern for society. Data on dementia in the oldest old have begun to be commonly available. For example, the prevalence of dementia for persons older than 90 years in Western Europe has been estimated at 48% for women and 33% for men. In Switzerland, more than half of the nonagenarians live at home. After age 80, the proportion of persons living in nursing homes rises sharply. More than 70% of those institutionalized over 75 suffer from dementia.[2, 3] However, little is known about their psychological state and the presence of psychopathological features because of a lack of specific studies.
Among the common symptoms observed in this specific population, seemingly in relation to the high prevalence of dementia, is unawareness of one's own deficits, a complex notion that could be described as an impaired ability to see oneself from a third-person perspective. Unawareness is preferentially viewed as a dimensional rather than categorical function, with various methods of assessment producing different outcomes. There is no perfect tool to assess unawareness as a whole. Anosognosia covers generally a narrower range than the concept of impaired insight. Lack of insight could be considered intrinsic to mental illness, a psychological reaction to mental illness or shaped by environmental factors. Anosognosia was first linked to the recognition of neurological deficits, to neurological and neuropsychological impairment, and distances itself from denial, which implies psychological mechanisms.
As anosognosia seems strikingly frequent and empirically problematic in clinical settings, we have chosen to focus specifically on anosognosia, a limited but extensively explored aspect of unawareness, and its links with other cognitive and psychopathological deficits. In younger subjects, anosognosia has been correlated to a threefold increase in the risk of dangerous behaviours or putting oneself at risk for neglect; it is also a predictor of apathy in Alzheimer's disease. Anosognosia is closely associated with cognitive decline and psychiatric and behavioural disorders. More specifically, higher anosognosia is associated with lower depression scores. Depressive symptoms, including dysthymia but less clearly major depressive disorder, may have a potentially confounding effect between anosognosia and dementia severity, as people with depression show less diminished insight. In nursing homes, the prevalence of depression seems to be slightly lower in the very old than in younger subjects: 8.9% for persons aged 85 and older versus 13.3% for those aged 65–74. Residing in a nursing home is indicative of more frequent and increased depressive symptoms in the oldest old.
In this study, we hypothesized that anosognosia is related to cognitive and/or psychiatric disorders in the oldest old. As is the case in younger subjects, the magnitude of anosognosia depends on the severity of the symptoms. We expect that higher positive scores correlate with higher cognitive impairment, whereas negative scores correlate with depressive symptoms.
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The main findings of this study are the frequent occurrence of affective symptoms and mild anosognosia in the elderly dwelling in geriatric nursing homes. The magnitude of anosognosia was associated with symptoms of apathy and agitation. Depression, anxiety and apathy were the three most common neuropsychiatric symptoms in our sample. Unlike in younger subjects, depression is not associated with increased mortality hazards in this population. Similarly, in our study, there were no correlations between physical comorbidities and neuropsychiatric symptoms, including depressive symptoms.
As in other studies, our results show that anosognosia has a negative correlation with the total MMSE score, which has also been found with younger subjects, as well as with executive functioning assessed with the CLOX test and with categorical and lexical fluencies. There is no correlation between anosognosia and age itself in our very elderly sample. In the present nursing home sample, the weight of somatic comorbidities is moderate, but there is no association with anosognosia or cognitive functioning. Moreover, there has been little research on this topic. In our sample of oldest-old subjects, the anosognosia discrepancy score was positively correlated with apathy but not with depression, thus confirming findings of previous studies on younger subjects. Apathy was associated with poor awareness of cognitive and behavioural impairment, and was also associated with older age. Additionally, in the case of Alzheimer's dementia, apathy may be a marker of more malignant forms of Alzheimer's disease and a predictor of depression in Alzheimer's disease.
This study showed that the least cognitively impaired subjects tended to exaggerate their difficulties as compared to the descriptions made by their caregivers, which is also a form of anosognosia. Subjects with greater cognitive impairment generally minimized their difficulties relative to their caretakers' descriptions, whereas subjects with only mild cognitive impairment seemed to do the opposite. However, this trend did not reach the threshold of statistical significance; the least anosognosic were those with mild to moderate global cognitive impairment according to MMSE scores. Depressive symptoms may be a mediating factor between cognitive impairment and self-awareness, with subjects having depressive symptoms being less likely to demonstrate diminished insight. Indeed, depression has been shown to be negatively correlated with anosognosia, as higher anosognosia has been associated with lower depression scores. In addition, feelings of depression have been shown to predict a greater awareness of cognitive impairment in Alzheimer's dementia. Furthermore, sub-syndromal depression and anxiety have been associated with a higher level of awareness. We assume that there might be some intrinsic depressiveness in this group of oldest old. Remarkably, depression prevalence may increase substantially with age in non-demented patients, as the prevalence of depression in nonagenarians is twice as high as in octogenarians.
Biologic ageing of the brain may induce an elevated vulnerability for increased incidence of diseased states, including corticolimbic disruption and low mood associated with depression. Additionally, institutional status may reflect increased depressive symptoms for centenarians without cognitive impairment or with mild cognitive impairment. Some authors have found that there is an unequal frequency of overestimation by patients of essentially instrumental deficits as opposed to functional deficits in the case of major or minor depression. Others have reported an overestimation of cognitive deficits in mild cognitive impairment in contrast to Alzheimer's disease patients, but the conclusions are controversial and not shared by others who have found an association with unawareness, even in cases of slight cognitive impairment. This apparent contradiction could be explained by the multidimensionality of awareness and the various assessment methods used.
The tests we have used have several limitations. A specific depression scale should be used in further studies to better characterize affective symptoms. The depression subscale of the NPI is probably too little discriminating and has shown no correlation with anosognosia in previous studies or in ours. The relationship between insight, depression and dementia is manifold, as depression in dementia patients is likely to arise from intertwined biological and psychological processes. The low amplitude of symptoms measured with the NPI subscales suggests the need for the development of a specific instrument to assess psychopathological features and offer a possible explanation of the negative discrepancy of anosognosia scores for the least cognitively impaired subjects. Another limitation of the present study is that the AQ-D, though widely used, only measures some targets of unawareness, specifically those associated with basic and instrumental activities of daily living and changes in mood and behaviour. Many other aspects of self-awareness regarding, such as moral judgement or prospective memory, are not assessed by this scale. Cognitive deficiency has been shown to induce a heterogeneous impairment of self-consciousness. Thus, anosognosia as measured in this study may only reflect some fragmentary aspects of this reality. Because of the method of administration, results depend on the reliability of the caregivers' answers. In discrepancy methods, it may be difficult to distinguish between overestimations made by subjects and underestimations made by others. Carer evaluation depends on the type and quality of the relationship and time spent with the subject. By interviewing a professional daily caregiver, we assume that the interviewee bias was more limited than it would have been for a relative.
Testing nonagenarians and centenarians requires adjustment because of frequent sensorimotor disturbances, lower speed, and the lack of validated tools for this age category. Testing procedures need to be adapted, and appropriate tests have to be used. Thus, sensory impairment did not affect the results as we selected tests that were easy to administer and adjusted font size and speech volume when needed.
Anosognosia in the oldest old was mostly mild and strongly associated with global and specific cognitive functions and psychopathological alteration as in younger subjects. There was, however, a different trend for the least cognitively impaired, who tended to exaggerate their difficulties.
An extension to a community-dwelling sample would help clarify the role of age itself in anosognosia in the least cognitively impaired subjects, identify any causal relationship between anosognosia and the psychopathological features observed, and specify the possible role of mediating factors to explain if this emphasis on one's perceived difficulties is a particular feature of the institutionalized very elderly or a defining characteristic of the cognitively unimpaired oldest old.