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Introdução: Em estudos de ressonância magnética (RM) estrutural e tomografia por emissão de pósitrons (positron emission tomography; PET), métodos de análise voxel-a-voxel permitem comparações entre grupos do volume de substância cinzenta ou do metabolismo de glicose de forma automatizada, em todo o cérebro. Em estudos com portadores de transtornos cognitivos como a Demência de Alzheimer (DA) comparados a controles saudáveis, tais métodos mostram alterações não só em regiões cerebrais classicamente envolvidas na DA (como hipocampo), mas também em áreas não investigadas anteriormente. Mesmo na ausência de demência, sujeitos idosos apresentam freqüentemente alterações cognitivas, sobretudo em associação com fatores de risco cardiovascular, tais como hipertensão arterial sistêmica. Metodologia: Foi realizado numa amostra de 265 idosos na faixa etária entre 66 e 75 anos exames de RM. A amostra foi dividida em dois grupos, o primeiro com perda cognitiva compatível com diagnóstico prejuízo cognitivo (caracterizado pelo desempenho de 1.5 desvio padrão abaixo da média do grupo) e o segundo grupo sem perda cognitiva. A presença de alterações cerebrais associadas à presença de déficit cognitivos entre os grupos foi investigada utilizando uma metodologia automatizada de avaliação voxel-a-voxel através do SPM. Resultados: Identificamos 5 sujeitos com prejuízo cognitivo numa amostra populacional de 244 indivíduos. A presença de prejuízo cognitivo foi associada à presença de lesão silenciosa (p=0,001), idade (p=0,002), e a presença de diabetes (p=0,026). Prejuízos no desempenho cognitivo total foram associados à redução de SC envolvendo o hipocampo e giro parahipocampal à direita (p=0,049 e p=0,036, respectivamente). Prejuízos no desempenho em tarefas de memória foram associados à redução de SC envolvendo regiões de hipocampo, giro parahipocampal e amídala à esquerda (p=0,026, p=0,031, e p=0,007, respectivamente). Prejuízos em tarefas de atenção foram associados à redução de SC envolvendo hipocampo e giro parahipocampal à esquerda (p=0,019 e p=0,013, respectivamente). Finalmente, prejuízos no desempenho cognitivo em tarefas fluência verbal foram associados à redução de SC envolvendo córtex temporal medial à direita (p=0,041). Conclusão: A presença de prejuízo cognitivo foi observada numa pequena porcentagem da população geral quando avaliada através da comparação com o desempenho no próprio grupo. Estudo de volumetria cerebral, após exclusão dos sujeitos com lesão silenciosa, observou que o desempenho cognitivo de idosos da comunidade apresentou relação direta com o volume cerebral de regiões límbicas, importantes para a cognição e memória. / Introduction: In studies with structural magnetic resonance imagery (MRI) and positron emission tomography (PET), methods of analysis voxel-by-voxel allow comparisons among groups of gray matter volume or glucose metabolisms in an automatized fashion all around the brain. In studies with cognitive disorder carriers, such as Alzheimer\'s Disease (AD) compared to healthy controls, such methods show alterations not only in the brain regions classically involved in AD (such as hippocampus), but also in areas not previously investigated. Even in the absence of dementia, elderly people often present cognitive changes, mainly in association with cardiovascular risk factors, such as systemic arterial hypertension. Methodology: We performed MRI in a sample of 265 elderly people in the age range between 66 to 75 years old. The sample was divided in two groups: the first one with cognitive loss compatible to cognitive impairment diagnosis (characterized by the performance of 1.5 standard deviation below the group average) and the second group without cognitive loss. The presence of brain alterations associated to the presence of cognitive deficits between the groups was investigated using an automatized methodology of voxel-to-voxel evaluation through statistical parametric mapping (SPM). Results: It was identified 5 subjects with cognitive impairment in a population sample of 244 individuals. The presence of cognitive impairment was associated to the presence of silent lesion (p=0.001), age (p=0.002), and the presence of diabetes (p=0.026). Impairments in the overall cognitive performance were associated to the reduction of the gray matter (GM) involving the hippocampus and parahippocampal gyrus to the right (p=0.049 and p=0.036, respectively). Impairments in the performance of memory tasks were associated to the reduction of GM involving the hippocampus, parahippocampal gyrus and amygdala regions to the left (p=0.026, p=0.031, and p=0.007, respectively). Impairments in attention tasks were associated to the reduction of GM involving the hippocampus and the parahippocampal gyrus to the left (p=0.019 and p=0.013, respectively). Finally, impairments in the cognitive performance of verbal fluency tasks were associated to the reduction of GM involving the medial temporal cortex to the right (p=0.041). Conclusion: The presence of cognitive impairment was observed in a small percentage of the general population when evaluated through the comparison of the performance in the group itself. The study of brain morphometry after the exclusion of subjects with silent lesion observed that the cognitive performance of the elderly people from the community presented direct relationship with the brain volume of the limbic regions, important for the cognition and memory.

[Truncated abstract] Background: Dementia, largely due to Alzheimer's disease (AD), is a major public health problem. The early identification of disease is an important challenge for clinicians because treatment of AD is now available. A simple and accurate means of stratifying risk for AD and identifying early disease is needed so that risk factor modification and treatment can occur optimally. To date, despite many attempts, an accurate means of standardising an approach to the assessment of subtle cognitive symptoms has not been developed. A subjective complaint of poor memory has been identified as a possible marker for underlying brain disease. This study examines the utility of neuropsychological scores, homocysteine levels, APOE genotyping and brain imaging as predictors of cognitive decline in individuals with subjective memory complaint (SMC). Method Eighty subjects with SMC were recruited from memory clinics and the community (MC: 1). Forty-two control subjects were also examined (MC: 0). CAMDEX was used to describe baseline clinical features. The CAMCOG was used as a global test of cognition and was administered annually for four years. At baseline, neuropsychological testing was administered. Cranial CT scanning, measurement of plasma homocysteine and APOE genotyping were completed. Categorical variables were analysed using chi-square according to Pearson's method. Continuous data was analysed using Student's t-tests and Mann-Whitney tests. A logistic regression model was used to identify independent contributors to the presence of memory complaint. Participants were then matched for age, gender and time to follow-up (up for three years) to determine longitudinal predictors of cognitive decline. ... Baseline CAMCOG scores were greater in the control group (MC:0 = 98.3 ? 2.8, MC:1 94.2 ? 5.5, Z ?4.46, p 0.000). There were no differences in neuropsychological scores, concentration of total plasma homocysteine, APOE genotype or brain scan measurements. Using the Wald stepwise selection method, logistic regression could not be established due to non-convergence regardless of whether or not the continuous variables were re-coded into dichotomous variables. A matching process that created 32 pairs of controls/subjects allowed follow-up analysis. The controls showed significant improvement with time on the CAMCOG unlike subjects (mean ? SD, controls 1.5 ?-3.0, Z - 2.61, p 0.01, subjects 0.2 ? 3.2, Z ? 0.24, p 0.81). The logistic regression analysis showed that group membership could not be defined by any single independent variable. When group membership was abandoned and those with stable scores were compared to those who declined no clear meaningful independent predictors of decline apart from age were identified. Conclusions: Methodological issues such as small sample size and inadequate follow up duration were identified that may have precluded identification of predictive factors for cognitive decline. The results indicate that complaints of memory problems are not associated with established risk factors for Alzheimer's disease and fail to predict objective cognitive decline over three years. Future studies should continue trying to identify robust predictors of cognitive decline in later life.

With the growing prevalence of bilingualism in modern society, it has become increasingly important to understand how the ability to speak more than one language affects cognitive function across the lifespan. Although bilingualism has been associated with disadvantages in measures of language use, bilinguals appear to demonstrate superior executive functioning compared to monolinguals. This “bilingual advantage” has been found for several aspects of cognitive control, including attention, inhibition and conflict resolution. Based on the overlap between cognitive networks and brain regions affected by aging, it has been further proposed that cognitive control—and by extension, bilingualism—confers protective effects against cognitive decline associated with natural aging. Here, we review the behavioral performance of bilinguals on linguistic and cognitive control measures, as well as evaluating information on the neural correlates of bilingualism and its relation to cognitive control and cognitive decline. An assessment of the present literature suggests that, compared to monolingual performance, the bilingual advantage in cognitive control carries over to a reasonable protective effect against cognitive decline. However, the lack of integrated research in the field demonstrates a need for further exploration of the specific facets of bilingualism, its potential significance for neurodegenerative diseases (e.g., Alzheimer’s disease), and the role of bilingualism in cognitive reserve.

La précarité est associée à une morbi-mortalité accrue. Ce phénomène est moins étudié auprès des sujets âgés qu’il ne l’est auprès des adultes jeunes. Pourtant, le vieillissement démographique et la précarisation de la population font que la France connait chaque jour davantage de personnes présentant cette double caractéristique d’être âgées et précaires. L’objectif de cette thèse est de mieux caractériser les liens existant entre la précarité – définie en son sens initial psycho-socio-économique – et deux problématiques du vieillissement que sont la cognition et la fragilité. Nous avons tout d’abord étudié le vieillissement cognitif au cours de 25 années de suivi de la cohorte Paquid. Cette étude a rapporté un déclin cognitif et un risque de démence majorés pour les personnes âgées précaires. Par la suite, nous avons complété cette première étude en y intégrant une mesure de précarité géographique et en appliquant une méthodologie statistique prenant en compte le risque compétitif de décès. Les résultats ont confirmé l’association entre la précarité psycho-socio-économique et le risque de démence, mais n’ont montré aucun effet de la précarité géographique. Mis en perspective avec les différents travaux scientifiques, ces études ont servi de base à une revue de la littérature sur l’impact de la précarité sur le vieillissement cognitif soumise pour publication. Enfin, un dernier travail a examiné les relations entre la précarité psycho-socio-économique, la fragilité et le décès. Sur la base de 14 années de suivi de la cohorte des 3 Cités, les résultats ont montré qu’aussi bien la précarité que la fragilité augmentent le risque de mortalité mais de manière indépendante. Ces travaux permettent de mieux comprendre ce qu’implique vieillir en situation de précarité et soulignent en particulier l’influence des déterminants psycho-sociaux de la précarité sur la santé, aussi bien en termes de survie que de santé cognitive. / Precariousness is associated with higher morbi-mortality. This phenomenon is less studied among the elderly than it is among adults. Yet, the aging of the population, as well as the increasing precariousness of the population, implies that a growing number of people in France are experiencing both conditions of aging and precariousness. The objective of this thesis is to better characterize the links between precariousness - defined with a psychosocioeconomic approach - and two issues related to aging: cognition and frailty. We first studied cognitive aging over 25 years within the Paquid cohort study. This study reported an accelerated cognitive decline and an increased risk of dementia for the precarious elderly. Then, this study was completed by including a measure of geographical deprivation and by applying a statistical methodology taking into account the competing risk of death. The results confirmed the association between psychosocioeconomic precariousness and the risk of dementia, but did not show any effects of geographical deprivation. In link with previous scientific literature, these two works have been the basis of a literature review on the impact of precariousness on cognitive aging submitted for publication. A final study examined the relationship between psychosocioeconomic precariousness, frailty and death. Based on the 14 years of follow-up of the 3 Cities cohort study, the results showed that both precariousness and frailty increased the risk of death but independently. This thesis contributes to a better understanding of the impact of precariousness on aging and in particular, it emphasizes the influence of the psychosocial determinants of precariousness on health in terms of survival and better cognition.