Personality and lifestyle in relation to dementia incidence

Aging Research Center, Dept. Neurobiology, Care Sciences and Society, Karolinska Institutet, Gävlegatan 16, 113 30 Stockholm, Sweden.
Neurology (Impact Factor: 8.3). 02/2009; 72(3):253-9. DOI: 10.1212/01.wnl.0000339485.39246.87
Source: PubMed

ABSTRACT High neuroticism has been associated with a greater risk of dementia, and an active/socially integrated lifestyle with a lower risk of dementia. The aim of the current study was to explore the separate and combined effects of neuroticism and extraversion on the risk of dementia, and to examine whether lifestyle factors may modify this association.
A population-based cohort of 506 older people with no dementia from the Kungsholmen Project, Stockholm, Sweden, was followed up for an average of 6 years. Personality traits were assessed using the Eysenck Personality Inventory. Dementia was diagnosed by specialists according to DSM-III-R criteria.
Neither high neuroticism nor low extraversion alone was related to significantly higher incidence of dementia. However, among people with an inactive or socially isolated lifestyle, low neuroticism was associated with a decreased dementia risk (hazard ratio [HR] = 0.51, 95% confidence interval [CI] = 0.27-0.96). When compared to persons with high neuroticism and high extraversion, a decreased risk of dementia was detected in individuals with low neuroticism and high extraversion (HR = 0.51, 95% CI = 0.28-0.94), but not among persons with low neuroticism and low extraversion (HR = 0.95, 95% CI = 0.57-1.60), nor high neuroticism and low extraversion (HR = 0.97 95% CI = 0.57-1.65). Stratified analysis by lifestyle showed that the inverse association of low neuroticism and high extraversion in combination was present only among the inactive or socially isolated persons.
Low neuroticism in combination with high extraversion is the personality trait associated with the lowest dementia risk; however, among socially isolated individuals even low neuroticism alone seems to decrease dementia risk.

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    ABSTRACT: Demographic forecasts predict a rapid growth of the aged population in western societies. With regard to this demographic development an important goal in cognitive neuroscience research is to identify modifiable factors that help maintain cognitive functioning in old age. Among these, lifestyle and health related factors have become important pillars of current research on effective mechanisms for warding off structural and functional decline in the aging brain. Age-related decline in learning and memory, often termed as age-associated memory impairment (AAMI), is a well-documented finding in healthy old adults but the neurobiological underpinnings of this decline are still under debate. A consistent pattern of AAMI is a decrement in episodic memory apparent in impaired free recall and recollection. Evidence from lesion studies in humans and animals indicate that episodic memory is critically dependent on the integrity of the medial temporal lobes (MTL) and the prefrontal cortex. However, it has also been pointed out that AAMI is also a result of age-related dysfunction in the neuromodulation of the areas mentioned (dopaminergic and cholinergic neuromodulation). The focus of this study is to investigate the influence that age-related structural changes within the regions of origin of dopaminergic and cholinergic neuromodulation exert on learning and memory in aging and how health and lifestyle related factors (eg. body-mass-index (BMI) years of education, subjective mental health, sense of coherence (SOC) and coping might influence this relationship. A cross-sectional-study with 86 healthy older adults (age-range: 65-84 years) and 24 young adults (age-range: 18-30 years) was carried out to investigate these relationships. We observed a robust positive correlation between the structural integrity of the SN/VTA (the main origin of dopaminergic projections) and verbal learning and memory performance among older adults. We found that BMI had an impact on the SN/VTA integrity: older people with high BMI showed a reduced SN/VTA integrity compared to older people with a lower BMI. Basal forebrain integrity, main origin of cholinergic neurotransmission showed a significant relationship not only with learning and memory but also with working memory span. In contrast, lifestyle factors such as job prestige, years of education, positive coping, sense of coherence showed a weak impact on cognitive variables. In a voxel-based morphometry study we investigated the relationship between the sense of coherence (SOC) and structural changes in gray matter. The SOC is a subjective assessment of the ability of future oriented planning and prediction and to learn from prediction-errors. Sub-categories of this measure showed a robust correlation with gray matter density of the posterior cingulum (PCC). This finding has implications for developing early markers of Mild Cognitive Impairment (MCI) because where the PCC is one of the regions affected in early stages. Also, the PCC is implicated in episodic and prospective memory performance. The findings of this study will be discussed within a model which combines the taking into account the role of dopamine in novelty-processing as well as in explorative behaviours. On the basis of these findings it is possible to design new screening methods, which capture specific relationships between psychosocial factors and brain structures, like SN/VTA and PCC to better predict MCI. A long-term goal is to develop new lifestyle and health based strategies for prevention.
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