Hui-Xin Wang

Influence of social network on occurrence of dementia: a community-based longitudinal study

BACKGROUND Few data are available on the effect of social ties on dementia development. This study explored whether single social network components and different degrees of the social connections affect dementia incidence. METHODS A community-based cohort of 1203 non-demented people, living at home in the Kungsholmen district of Stockholm, Sweden, and who had good cognition, was followed for an average period of 3 years. On the basis of medical and psychological data, 176 patients were diagnosed with dementia according to the criteria of the third edition revision of the Diagnostic and Statistical Manual of Mental Disorders. Information on social network was obtained by personal interview by trained nurses at baseline. The covariates included in the analysis were age, sex, education, cognitive and functional status, depressive symptoms, and vascular diseases. FINDINGS Those individuals living alone, and those without any close social ties, both had an adjusted relative risk for developing dementia of 1.5 (95% CI 1.0-2.1 and 1.0-2.4, respectively). Compared with married people living with someone, single people and those living alone had an adjusted relative risk of 1.9 (95% CI 1.2-3.1). Infrequent contacts with network resources did not increase the risk of the disease if such contacts were experienced as satisfying. When all components were combined in an index, a poor or limited social network increased the risk of dementia by 60% (95% CI 1.2-2.1), and a significant gradient was found for the four degrees of social connections (p=0.0009). INTERPRETATION An extensive social network seems to protect against dementia. Confirmation of this finding and further investigation to clarify the mechanisms are worthwhile due to the implications for prevention.

Vitamin B12 and folate in relation to the development of Alzheimer’s disease

Objective: To explore the associations of low serum levels of vitamin B12 and folate with AD occurrence. Methods: A population-based longitudinal study in Sweden, the Kungsholmen Project. A random sample of 370 nondemented persons, aged 75 years and older and not treated with B12 and folate, was followed for 3 years to detect incident AD cases. Two cut-off points were used to define low levels of vitamin B12 (≤150 and ≤250 pmol/L) and folate (≤10 and ≤12 nmol/L), and all analyses were performed using both definitions. AD and other types of dementia were diagnosed by specialists according to DSM-III-R criteria. Results: When using B12 ≤150pmol/L and folate ≤10 nmol/L to define low levels, compared with people with normal levels of both vitamins, subjects with low levels of B12 or folate had twice higher risks of developing AD (relative risk [RR] = 2.1, 95% CI = 1.2 to 3.5). These associations were even stronger in subjects with good baseline cognition (RR = 3.1, 95% CI = 1.1 to 8.4). Similar relative risks of AD were found in subjects with low levels of B12 or folate and among those with both vitamins at low levels. A comparable pattern was detected when low vitamin levels were defined as B12 ≤250 pmol/L and folate ≤12 nmol/L. Conclusions: This study suggests that vitamin B12 and folate may be involved in the development of AD. A clear association was detected only when both vitamins were taken into account, especially among the cognitively intact subjects. No interaction was found between the two vitamins. Monitoring serum B12 and folate concentration in the elderly may be relevant for prevention of AD.

Mental, Physical and Social Components in Leisure Activities Equally Contribute to Decrease Dementia Risk

Background: There is accumulating evidence in the literature that leisure engagement has a beneficial effect on dementia. Most studies have grouped activities according to whether they were predominantly mental, physical or social. Since many activities contain more than one component, we aimed to verify the effect of all three major components on the dementia risk, as well as their combined effect. Methods: A mental, social and physical component score was estimated for each activity by the researchers and a sample of elderly persons. The correlation between the ratings of the authors and the means of the elderly subjects’ ratings was 0.86. The study population consisted of 776 nondemented subjects, aged 75 years and above, living in Stockholm, Sweden, who were still nondemented after 3 years and were followed for 3 more years to detect incident dementia cases. Results: Multi-adjusted relative risks (RRs) of dementia for subjects with higher mental, physical and social component score sums were 0.71 (95% CI: 0.49–1.03), 0.61 (95% CI: 0.42–0.87) and 0.68 (95% CI: 0.47–0.99), respectively. The most beneficial effect was present for subjects with high scores in all or in two of the components (RR of dementia = 0.53; 95% CI: 0.36–0.78). Conclusions: These findings suggest that a broad spectrum of activities containing more than one of the components seems to be more beneficial than to be engaged in only one type of activity.

Brain reserve hypothesis in dementia.

The concept of brain reserve refers to the ability to tolerate the age-related changes and the disease related pathology in the brain without developing clear clinical symptoms or signs. A considerable body of biological research has documented that a number of factors including education, work complexity, social network, and leisure activities may contribute to this reserve allowing cognitive function to be maintained in old ages. Epidemiological studies have also related these factors to the development of dementia, suggesting that intellectual challenges experienced across the whole life span may increase the brain reserve and be crucial for the occurrence of dementia symptoms in late life. This paper is a systematic review of the published epidemiological studies on this topic. The availability of numerous epidemiological and biological data investigating the reserve hypothesis in dementia permits some preliminary conclusions. High education, adult-life occupational work complexity, as well as a mentally and socially integrated lifestyle in late life could postpone the onset of clinical dementia and AD. The relevance of physical activity itself remains in debate, as most physical activities include also social and mental stimulation. Leisure activities with all three components--physical, mental and social--seem to have the most beneficial effect. Delaying dementia onset by five years would halve dementia prevalence and substantially decrease the number of dementia cases in the community.

Smoking and Parkinson’s and Alzheimer’s disease: review of the epidemiological studies

The relationship between smoking and neurological diseases has always been controversial. Even the expected association between smoking and increased risk for cerebrovascular disease has been debated for years. It was at the end of the 1980s that smoking became definitively accepted as a risk factor for ischemic stroke. More recently, two other neurological diseases have been studied in relation to smoking: Parkinsons disease (PD) and Alzheimers disease (AD). Many epidemiological studies have found a highly significant negative association between cigarette smoking and these two neurodegenerative disorders. The risk of AD or PD in nonsmokers has generally been about twice that of smokers. That is, patients with AD or PD are approximately 50% less likely to have smoked cigarettes during their lifetime than are age- and gender-matched controls. Alternatively, cigarette smokers are 50% less likely to have PD or AD than are age- and gender-matched nonsmokers. This statistically significant negative association has been interpreted as suggesting that cigarette smoking exerts an undefined, biologic, neuroprotective influence against the development of PD and AD. A review of all studies that either support or refute this hypothesis is presented separately for PD and AD.

Accelerated Progression from Mild Cognitive Impairment to Dementia in People with Diabetes

OBJECTIVE The effect of diabetes on mild cognitive impairment (MCI) and its conversion to dementia remains controversial. We sought to examine whether diabetes and pre-diabetes are associated with MCI and accelerate the progression from MCI to dementia. RESEARCH DESIGN AND METHODS In the Kungsholmen Project, 963 cognitively intact participants and 302 subjects with MCI (120 with amnestic MCI [aMCI ] and 182 with other cognitive impairment no dementia [oCIND]) age ≥75 years were identified at baseline. The two cohorts were followed for 9 years to detect the incident MCI and dementia following international criteria. Diabetes was ascertained based on a medical examination, hypoglycemic medication use, and random blood glucose level ≥11.0 mmol/l. Pre-diabetes was defined as random blood glucose level of 7.8–11.0 mmol/l in diabetes-free participants. Data were analyzed using standard and time-dependent Cox proportional-hazards models. RESULTS During the follow-up period, in the cognitively intact cohort, 182 people developed MCI (42 aMCI and 140 oCIND), and 212 developed dementia. In the MCI cohort, 155 subjects progressed to dementia, the multi-adjusted hazard ratio (95% CI) of dementia was 2.87 (1.30–6.34) for diabetes, and 4.96 (2.27–10.84) for pre-diabetes. In a Kaplan-Meier survival analysis, diabetes and pre-diabetes accelerated the progression from MCI to dementia by 3.18 years. Diabetes and pre-diabetes were neither cross-sectionally nor longitudinally associated with MCI. CONCLUSIONS Diabetes and pre-diabetes substantially accelerate the progression from MCI to dementia, and anticipate dementia occurrence by more than 3 years in people with MCI. The association of diabetes with the development of MCI is less evident in old people.

Leisure activities, cognition and dementia

Accumulated evidence shows that leisure activities have a positive impact on cognitive function and dementia. This review aimed to systematically summarize the current evidence on this topic taking into account the limitations of the studies and biological plausibility for the underlying mechanisms linking cognition, dementia and leisure activities, with special attention on mental, physical and social activities. We included only longitudinal studies, with a follow-up time of at least 2 years, published in English from 1991 to March 2011 on leisure activities and cognition (n=29) or dementia (n=23) and provided some evidence from intervention studies on the topic. A protective effect of mental activity on cognitive function has been consistently reported in both observational and interventional studies. The association of mental activity with the risk of dementia was robust in observational studies but inconsistent in clinical trials. The protective effect of physical activity on the risk of cognitive decline and dementia has been reported in most observational studies, but has been less evident in interventional studies. Current evidence concerning the beneficial effect of other types of leisure activities on the risk of dementia is still limited and results are inconsistent. For future studies it is imperative that the assessment of leisure activities is standardized, for example, the frequency, intensity, duration and the type of activity; and also that the cognitive test batteries and the definition of cognitive decline are harmonized/standardized. Further, well designed studies with long follow-up times are necessary. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.

Psychosocial stress and atherosclerosis: family and work stress accelerate progression of coronary disease in women. The Stockholm Female Coronary Angiography Study

Objective.  To examine the impact of psychosocial stress, experienced in the family and work life, on the progression of coronary atherosclerosis in women cardiac patients.

Personality and lifestyle in relation to dementia incidence

Objective: 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. Methods: 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. Results: 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. Conclusion: 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.

Late Life Leisure Activities and Risk of Cognitive Decline

BACKGROUND Studies concerning the effect of different types of leisure activities on various cognitive domains are limited. This study tests the hypothesis that mental, physical, and social activities have a domain-specific protection against cognitive decline. METHODS A cohort of a geographically defined population in China was examined in 2003-2005 and followed for an average of 2.4 years. Leisure activities were assessed in 1,463 adults aged 65 years and older without cognitive or physical impairment at baseline, and their cognitive performances were tested at baseline and follow-up examinations. RESULTS High level of mental activity was related to less decline in global cognition (β = -.23, p < .01), language (β = -.11, p < .05), and executive function (β = -.13, p < .05) in ANCOVA models adjusting for age, gender, education, history of stroke, body mass index, Apolipoprotein E genotype, and baseline cognition. High level of physical activity was related to less decline in episodic memory (β = -.08, p < .05) and language (β = -.15, p < .01). High level of social activity was associated with less decline in global cognition (β = -.11, p < .05). Further, a dose-response pattern was observed: although participants who did not engage in any of the three activities experienced a significant global cognitive decline, those who engaged in any one of the activities maintained their cognition, and those who engaged in two or three activities improved their cognition. The same pattern was observed in men and in women. CONCLUSIONS Leisure activities in old age may protect against cognitive decline for both women and men, and different types of activities seem to benefit different cognitive domains.