Trace element levels in drinking water and cognitive function among elderly Chinese

Association between drinking water sources and cognitive functioning in Chinese older adults residing in rural areas

OBJECTIVES

To explore the association between drinking water sources and cognitive functioning among older adults residing in rural China.

METHODS

Data were extracted from the 2008-2018 Chinese Longitudinal Healthy Longevity Survey. Drinking water sources were categorized according to whether purification measures were employed. The Chinese version of the Mini-Mental State Examination was used for cognitive functioning assessment, and the score of <24 was considered as having cognitive dysfunction. Cox regression analyses were conducted to derive hazard ratios (HRs) and 95% confidence intervals (CIs) for the effects of various drinking water sources, changes in such sources, and its interaction with exercise on cognition dysfunction.

RESULTS

We included 2304 respondents aged 79.67 ± 10.02 years; of them, 1084 (44.49%) were men. Our adjusted model revealed that respondents consistently drinking tap water were 21% less likely to experience cognitive dysfunction compared with those drinking untreated water (HR = 0.79, 95% CI: 0.70-0.90). Respondents transitioning from natural to tap water showed were 33% less likely to experience cognitive dysfunction (HR = 0.67, 95% CI: 0.58-0.78). Moreover, the HR (95% CI) for the interaction between drinking tap water and exercising was 0.86 (0.75-1.00) when compared with that between drinking untreated water and not exercising. All results adjusted for age, occupation, exercise, and body mass index.

CONCLUSIONS

Prolonged tap water consumption and switching from untreated water to tap water were associated with a decreased risk of cognitive dysfunction in older individuals. Additionally, exercising and drinking tap water was synergistically associated with the low incidence of cognitive dysfunction. These findings demonstrate the importance of prioritizing drinking water health in rural areas, indicating that purified tap water can enhance cognitive function among older adults.

Association between the Composition of Drinking Water and Cognitive Function in the Elderly: A Systematic Review

The prevalence of dementia increases with nearly 10 million new cases each year, with Alzheimer's disease contributing to 60-70% of cases. Environmental factors such as drinking water have been evaluated to determine if a relationship exists between trace elements in drinking water and the risk of developing cognitive disorders in the elderly. The purpose of the current systematic review was to evaluate an association between the composition of drinking water and cognitive function in the elderly. In accordance with the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines, a literature search was conducted using PubMed and CINAHL databases. A total of 10 studies were included in the current systematic review. Aluminum is the most commonly evaluated trace element in studies (n = 8), followed by silica (n = 5), calcium (n = 4), and fluoride (n = 4). Aluminum exposure showed an increased risk of cognitive decline in four studies, with no association reported in the other studies. Higher silica and pH levels were shown to be protective against a decline in cognitive function. A similar protective effect of calcium was found in two studies. Future research should measure multiple trace mineral levels in all water sources to evaluate the impact on cognitive function.

The relationship between cadmium and cognition in the elderly: a systematic review

Context: The relationship between cadmium (Cd) and the cognition of the elderly is indistinct.Objective: To summarise the studies on the relationship between the cognition of the elderly and Cd.Methods: Literatures were searched in PubMed, Web of Science, China National Knowledge Infrastructure (CNKI), and Wan fang database on April 25, 2022. The entries in the STROBE statement were used to evaluate the literature quality; all the quantitative studies that met the requirements were systematically summarised.Results: Blood Cd was negatively correlated with the cognitive ability of the elderly, corresponding to different cognitive ability assessment methods, the regression coefficients were: -0.11 (-0.20, -0.03), -0.46 (-0.71, -0.21), -0.54 (-0.90, -0.17), -0.19 (-0.37, -0.01), and -2.29 (-3.41, -1.16). The regression coefficients between urinary Cd level and cognition score were -1.42 (-2.38, -0.46), and 0.76 (-1.28, -0.23). When dietary Cd increased by 1 μg/kg, the composite z-score decreased by 3.64 (p = 0.001). There was no significant correlation between drinking water Cd, fingernail Cd and cognition (p > 0.05).Conclusion: We concluded that blood Cd (including whole blood and plasma), urine Cd and dietary Cd were negatively correlated with the cognition of the elderly, but the relationship between Cd in drinking water and fingernails and cognition was not statistically significant.

The effect of water source on cognitive functioning in Chinese adults: A cross-sectional and follow-up study

The effect of water source on cognitive functioning is poorly understood. The present study explored the associations between water source and cognition in 9921 participants from the China Health and Retirement Longitudinal Study (CHARLS). Cognitive functioning was measured from three aspects: orientation and attention, episodic memory, and visuo-construction. Water sources included tap and non-tap water. Generalized linear models and multiple logistic regression models were conducted to investigate the associations of cognitive scores with water source among the whole population and different subgroups. Results from cross-sectional analysis reported that participants without access to tap water showed a lower cognitive score (β = - 0.57; 95% CI: - 0.74, - 0.39) than those with tap water as a water source; and this phenomenon was pronounced for both sexes and across all residences. During 4-years' follow-up, a greater decline of cognitive score was associated with no tap water use in the lowest quartile of baseline cognitive scores (β = - 0.67; 95% CI: - 1.26, - 0.08). Additionally, the utilization rate of tap water was lower in rural areas compared to urban areas. The lowest utilization rates were observed in urban areas of the Anhui province (0.38 in 2011 and 0.55 in 2015) and in rural areas of Inner Mongolia (0.09 in 2011 and 0.20 in 2015). These findings suggest that having no tap water may be a risk factor for cognition impairment, particularly for those with a low basic cognition score. Additionally, our results support the need to expand tap water use in China.

Plasma calcium concentration during detoxification predicts neural cue-reactivity and craving during early abstinence in alcohol-dependent patients

Recent studies on the pathophysiology of alcohol dependence suggest a link between peripheral calcium concentrations and alcohol craving. Here, we investigated the association between plasma calcium concentration, cue-induced brain activation, and alcohol craving. Plasma calcium concentrations were measured at the onset of inpatient detoxification in a sample of N = 115 alcohol-dependent patients. Alcohol cue-reactivity was assessed during early abstinence (mean 11.1 days) using a functional magnetic resonance imaging (fMRI) alcohol cue-reactivity task. Multiple regression analyses and bivariate correlations between plasma calcium concentrations, clinical craving measures and neural alcohol cue-reactivity (CR) were tested. Results show a significant negative correlation between plasma calcium concentrations and compulsive alcohol craving. Higher calcium levels predicted higher alcohol cue-induced brain response in a cluster of frontal brain areas, including the dorsolateral prefrontal cortex (dlPFC), the anterior prefrontal cortex (alPFC), and the inferior (IFG) and middle frontal gyri (MFG). In addition, functional brain activation in those areas correlated negatively with craving for alcohol during fMRI. Higher peripheral calcium concentrations during withdrawal predicted increased alcohol cue-induced brain activation in frontal brain areas, which are associated with craving inhibition and cognitive control functions. This might indicate that higher plasma calcium concentrations at onset of detoxification could modulate craving inhibition during early abstinence.Trial registration number: DRKS00003388; date of registration: 14.12.2011.

Immunomodulation by heavy metals as a contributing factor to inflammatory diseases and autoimmune reactions: Cadmium as an example

Cadmium (Cd) represents a unique hazard because of the long biological half-life in humans (20-30 years). This metal accumulates in organs causing a continuum of responses, with organ disease/failure as extreme outcome. Some of the cellular and molecular alterations in target tissues can be related to immune-modulating potential of Cd. This metal may cause adverse responses in which components of the immune system function as both mediators and effectors of Cd tissue toxicity, which, in combination with Cd-induced alterations in homeostatic reparative activities may contribute to tissue dysfunction. In this work, current knowledge concerning inflammatory/autoimmune disease manifestations found to be related with cadmium exposure are summarized. Along with epidemiological evidence, animal and in vitro data are presented, with focus on cellular and molecular immune mechanisms potentially relevant for the disease susceptibility, disease promotion, or facilitating development of pre-existing pathologies.

Drinking habits and water sources with the incidence of cognitive impairment in Chinese elderly population: The Chinese Longitudinal Healthy Longevity Survey

BACKGROUND

Little was known on whether drinking habits and water sources affected cognitive function. This study aimed to examine the associations of drinking habits and water sources with the incidence of cognitive impairment in the Chinese elderly population.

METHODS

Data were drawn from the Chinese Longitudinal Healthy Longevity Survey. All participants aged ≥ 60 years at baseline were potential eligible. Cognitive function was measured using the Chinese version of the Mini-Mental State Examination (CMMSE). Participants with the CMMSE score ≤ 24 were identified as cognitive impairment. Drinking habits included preferring to drink boiled water or un-boiled water. Water sources included well, surface water, spring, and tap water.

RESULTS

This study included 18034 participants. Participants drinking un- boiled water were more likely to develop cognitive impairment than those drinking boiled water (P< 0.001; HR: 1.269; and 95% CI: 1.128-1.427). Compared to drinking from a well, drinking from tap water at childhood, around aged 60 years, and present was associated with a lower incidence of cognitive impairment (all P< 0.001; HR: 0.672, 0.735, and 0.765; and 95% CI: 0.540-0.836, 0.686-0.788, and 0.723-0.810, respectively).

LIMITATIONS

The underline mechanisms behind the associations of drinking habits and water sources with the incidence of cognitive impairment were not fully explained.

CONCLUSIONS

Participants drinking un- boiled water were more likely to develop cognitive impairment. Meanwhile, compared to drinking from a well, drinking from tap water was associated with a lower incidence of cognitive impairment.

Calcium Carbonate Attenuates Withdrawal and Reduces Craving: A Randomized Controlled Trial in Alcohol-Dependent Patients

INTRODUCTION

Preclinical studies have shown that calcium seems to be the active component of the anti-craving drug acamprosate (Ca2+ bis-acetyl-homotaurinate). Clinical effects in humans have also indicated an association between increased calcium plasma concentration due to acamprosate treatment and better outcome relating to time to relapse and cumulative abstinence. In contrast, low calcium concentration in alcohol-dependent patients was related with craving for alcohol. The main goal of the trial was to investigate whether an oral calcium administration is able to affect craving, withdrawal, and relapse risk in alcohol-dependent patients.

METHODS

We conducted a single-blind, randomized, monocentric, controlled clinical two-arm trial in alcohol-dependent patients (Clinical Trials Registration: DRKS00011293). A total of 55 alcohol-dependent subjects received calcium carbonate (800 mg + 5 μg vitamin D) versus sodium bicarbonate (1,000 mg) daily during the 14 days of inpatient alcohol-withdrawal treatment.

RESULTS

Based on an intention-to-treat protocol, withdrawal intensity (assessed with CIWA-Ar) in the calcium carbonate group attenuated faster than in the sodium bicarbonate subgroup. Alcohol craving (assessed with OCDS) in the calcium carbonate subgroup was also significantly reduced versus the sodium bicarbonate subgroup.

CONCLUSION

Our data support earlier findings and show that treatment with calcium carbonate during alcohol withdrawal reduces symptoms of alcohol withdrawal as well as alcohol craving in a controlled clinical pilot study. Mode of actions will need to be determined to allow the further development of pharmacological interventions beyond Ca2+ bis-acetyl-homotaurinate.

Effect of environmental toxicants on neuronal functions

In the last few years, neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD) have attracted attention due to their high prevalence worldwide. Environmental factors may be one of the biggest reasons for these diseases related to neuronal dysfunctions. Most of neuronal disorders are strongly associated with pre- and postnatal exposure to environmental toxins released from industries. Some of the neurotoxic metals such as lead, aluminum, mercury, manganese, cadmium, and arsenic as well as some pesticides and metal-based nanoparticles have been involved in AD and PD due to their ability to produce senile/amyloid plaques and NFTs which are the main feature of these neuronal dysfunctions. Exposure to solvents is also majorly responsible for neurodegenerative disorders. The present review highlights the impact of omnipresent heavy metals with some other neurotoxins on human health and how they give rise to neuronal dysfunctions which in turn causes socio-economic consequences due to increasing pollution worldwide. Graphical abstract.

Relation between cadmium body burden and cognitive function in older men: A cross-sectional study in China

Cadmium (Cd) is a known neurotoxicant and its relation with cognition has been well studied in children. However, evidence linking Cd and cognitive function among older individuals is limited. To evaluate the association between Cd exposure and cognitive function in older age, we conducted a cross-sectional study involving 375 older men aged 60-74 years (mean age: 66.0 years) in Guangxi, China. Urinary Cd concentrations were measured. Cognitive function was assessed by the Chinese version of Mini-Mental State Examination (MMSE) and cognitive impairment was identified using education-specific cutoff points of MMSE scores. General linear regression and logistic regression models were applied to evaluate the associations of urinary Cd concentrations with MMSE scores and the risk of cognitive impairment, respectively. The median urinary Cd concentration of all participants was 1.58 μg/g creatinine. Urinary Cd levels were inversely associated with MMSE scores [β = -0.76; 95% confidence interval (CI): -1.28 to -0.23 for a 2-fold increase in urinary Cd]. A 2-fold increase in urinary Cd was associated with increased risk of cognitive impairment [adjusted odds ratio (OR) = 1.46; 95% CI: 1.14 to 1.86]. When urinary Cd levels were analyzed as quartiles, higher urinary Cd levels were also significantly associated with increased risk of cognitive impairment in a dose-response manner (adjusted OR = 2.68; 95% CI: 1.33 to 5.38 for the highest vs. lowest quartile; p for trend = 0.002). Our findings suggest that long-term exposure to Cd may have adverse consequences for older men's cognitive function, but these results need further confirmation.

Cadmium Exposure Impairs Cognition and Olfactory Memory in Male C57BL/6 Mice

Cadmium (Cd) is a heavy metal of high interest to the superfund initiative. Recent epidemiology studies have suggested a possible association between Cd exposure and cognitive as well as olfactory impairments in humans. However, studies in animal models are needed to establish a direct causal relationship between Cd exposure and impairments in cognition and olfaction. This study aims to investigate the toxic effect of Cd on cognition and olfactory function in mice. One group of 8-week-old C57BL/6 male mice was exposed to 3 mg/l Cd (in the form of CdCl2) through drinking water for 20 weeks for behavior tests and final blood Cd concentration analysis. The behavior tests were conducted before, during, and after Cd exposure to analyze the effects of Cd on cognition and olfactory function. Upon completion of behavior tests, blood was collected to measure final blood Cd concentration. Two additional groups of mice were similarly exposed to Cd for 5 or 13 weeks for peak blood Cd concentration measurement. The peak blood Cd concentration was 2.125-2.25 μg/l whereas the final blood Cd concentration was 0.18 μg/l. At this exposure level, Cd impaired hippocampus-dependent learning and memory in novel object location test, T-maze test, and contextual fear memory test. It also caused deficits in short-term olfactory memory and odor-cued olfactory learning and memory. Results in this study demonstrate a direct relationship between Cd exposure and cognitive as well as olfactory impairments in an animal model.

Metals and neurodegenerative diseases. A systematic review

Neurodegenerative processes encompass a large variety of diseases with different pathological patterns and clinical presentation such as Amyotrophic Lateral Sclerosis (ALS), Alzheimer Disease (AD) and Parkinson's disease (PD). Genetic mutations have a known causative role, but the majority of cases are likely to be probably caused by a complex gene-environment interaction. Exposure to metals has been hypothesized to increase oxidative stress in brain cells leading to cell death and neurodegeneration. Neurotoxicity of metals has been demonstrated by several in vitro and in vivo experimental studies and it is likely that each metal could be toxic through specific pathways. The possible pathogenic role of different metals has been supported by some epidemiological evidences coming from occupational and ecological studies. In order to assess the possible association between metals and neurodegenerative disorders, several case-control studies have also been carried out evaluating the metals concentration in different biological specimens such as blood/serum/plasma, cerebrospinal fluid (CSF), nail and hair, often reporting conflicting results. This review provides an overview of our current knowledge on the possible association between metals and ALS, AD and PD as main neurodegenerative disorders.

Blood cadmium levels and Alzheimer's disease mortality risk in older US adults

BACKGROUND

Cadmium, a ubiquitous environmental pollutant, exhibits potential neurotoxic risk. Although compelling evidence suggests cadmium accumulation has a role in the formation of amyloid-β plaques and neurofibrillary tangles, which are the hallmarks of Alzheimer's disease (AD) pathogenesis, the supporting evidence in humans is limited and conflicting. In this study, we investigated the association between blood cadmium levels and AD mortality among older adults by analyzing the prospective data from the 1999-2004 Third National Health and Nutrition Examination Survey (NHANES) and the Linked Mortality File.

METHODS

The data were obtained from the 1999-2004 NHANES and the NHANES (1999-2004) Linked Mortality File. A total of 4,064 participants aged ≥60 years old with available blood cadmium data and no other missing information on their questionnaires at baseline were included in this study. AD was denoted as G30 based on the ICD-10 underlying causes of death.

RESULTS

Of the 4,064 participants, 51 subjects died as a result of AD. Compared with participants with low blood cadmium levels (≤0.3 μg/L), those with high cadmium levels (>0.6 μg/L) exhibited a 3.83-fold (hazard ratio = 3.83; 95 % CI = 1.39-10.59) increased risk of AD mortality. In the Kaplan-Meier survival curves for cumulative AD mortality, higher levels of blood cadmium showed marginally significant association with increased mortality at baseline and in patients over 60 years of age (p = 0.0684).

CONCLUSIONS

We observed a significant association between blood cadmium levels and AD mortality among older adults in the US. Our findings suggest that environmental exposure to cadmium may be a risk factor for AD.

The relationship between cholesterol and cognitive function is homocysteine-dependent

Introduction

Previous studies have identified hyperlipidemia as a potential risk factor for dementia and Alzheimer’s disease. However, studies on cholesterol measured in late-life and cognitive function have been inconsistent. Few studies have explored nonlinear relationships or considered interactions with other biomarker measures.

Methods

A cross-sectional sample of 1,889 participants from four rural counties in the People’s Republic of China was included in this analysis. Serum total cholesterol, high-density lipoprotein, triglycerides, and homocysteine levels were measured in fasting blood samples. A composite cognitive score was derived based on nine standardized cognitive test scores. Analysis of covariance models were used to investigate the association between biomarker measures and the composite cognitive scores.

Results

There was a significant interaction between the homocysteine quartile group and the cholesterol quartile group on cognitive scores (P=0.0478). In participants with normal homocysteine levels, an inverse U-shaped relationship between total cholesterol level and cognitive score was found, indicating that both low and high cholesterol levels were associated with lower cognitive scores. In participants with high homocysteine levels, no significant association between cholesterol and cognition was found.

Conclusion

The relationship between cholesterol levels and cognitive function depends upon homocysteine levels, suggesting an interactive role between cholesterol and homocysteine on cognitive function in the elderly population. Additional research is required to confirm our findings in other populations, and to explore potential mechanisms underlying the lipid–homocysteine interaction.

Acamprosate produces its anti-relapse effects via calcium

Alcoholism is one of the most prevalent neuropsychiatric diseases, having an enormous health and socioeconomic impact. Along with a few other medications, acamprosate (Campral-calcium-bis (N-acetylhomotaurinate)) is clinically used in many countries for relapse prevention. Although there is accumulated evidence suggesting that acamprosate interferes with the glutamate system, the molecular mode of action still remains undefined. Here we show that acamprosate does not interact with proposed glutamate receptor mechanisms. In particular, acamprosate does not interact with NMDA receptors or metabotropic glutamate receptor group I. In three different preclinical animal models of either excessive alcohol drinking, alcohol-seeking, or relapse-like drinking behavior, we demonstrate that N-acetylhomotaurinate by itself is not an active psychotropic molecule. Hence, the sodium salt of N-acetylhomotaurinate (i) is ineffective in alcohol-preferring rats to reduce operant responding for ethanol, (ii) is ineffective in alcohol-seeking rats in a cue-induced reinstatement paradigm, (iii) and is ineffective in rats with an alcohol deprivation effect. Surprisingly, calcium salts produce acamprosate-like effects in all three animal models. We conclude that calcium is the active moiety of acamprosate. Indeed, when translating these findings to the human situation, we found that patients with high plasma calcium levels due to acamprosate treatment showed better primary efficacy parameters such as time to relapse and cumulative abstinence. We conclude that N-acetylhomotaurinate is a biologically inactive molecule and that the effects of acamprosate described in more than 450 published original investigations and clinical trials and 1.5 million treated patients can possibly be attributed to calcium.

Associations between cadmium exposure and neurocognitive test scores in a cross-sectional study of US adults

BACKGROUND

Low-level environmental cadmium exposure and neurotoxicity has not been well studied in adults. Our goal was to evaluate associations between neurocognitive exam scores and a biomarker of cumulative cadmium exposure among adults in the Third National Health and Nutrition Examination Survey (NHANES III).

METHODS

NHANES III is a nationally representative cross-sectional survey of the U.S. population conducted between 1988 and 1994. We analyzed data from a subset of participants, age 20-59, who participated in a computer-based neurocognitive evaluation. There were four outcome measures: the Simple Reaction Time Test (SRTT: visual motor speed), the Symbol Digit Substitution Test (SDST: attention/perception), the Serial Digit Learning Test (SDLT) trials-to-criterion, and the SDLT total-error-score (SDLT-tests: learning recall/short-term memory). We fit multivariable-adjusted models to estimate associations between urinary cadmium concentrations and test scores.

RESULTS

5662 participants underwent neurocognitive screening, and 5572 (98%) of these had a urinary cadmium level available. Prior to multivariable-adjustment, higher urinary cadmium concentration was associated with worse performance in each of the 4 outcomes. After multivariable-adjustment most of these relationships were not significant, and age was the most influential variable in reducing the association magnitudes. However among never-smokers with no known occupational cadmium exposure the relationship between urinary cadmium and SDST score (attention/perception) was significant: a 1 μg/L increase in urinary cadmium corresponded to a 1.93% (95%CI: 0.05, 3.81) decrement in performance.

CONCLUSIONS

These results suggest that higher cumulative cadmium exposure in adults may be related to subtly decreased performance in tasks requiring attention and perception, particularly among those adults whose cadmium exposure is primarily though diet (no smoking or work based cadmium exposure). This association was observed among exposure levels that have been considered to be without adverse effects and these levels are common in U.S. adults. Thus further research into the potential neurocognitive effects of cadmium exposure is warranted. Because cumulative cadmium exposure may mediate some of the effects of age and smoking on cognition, adjusting for these variables may result in the underestimation of associations with cumulative cadmium exposure. Prospective studies that include never-smokers and non-occupationally exposed individuals are needed to clarify these issues.

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.

Normative data for neuropsychological tests in a rural elderly Chinese cohort

Normative information is important for appropriate interpretation of cognitive test scores as a critical component of dementia diagnosis in the elderly population. A cross-sectional evaluation of 1826 participants aged 65 years and older from four rural counties in China was conducted using six cognitive instruments including tests of global cognitive function (the Community Screening Instrument for Dementia), memory (Word List Learning and Recall tasks from the Consortium to Establish a Registry for Alzheimer's Disease, IU Story), language (Animal Fluency Test), and executive function (IU Token). Multiple regression models adjusting for demographic variables were used to provide standardized residuals z-scores and corresponding percentile ranking for each cognitive test. In all cognitive tests older age was associated with worse test performance while exposure to education was related to better cognitive test performance. We also detected a significant gender difference with men scoring better than women and a significant gender by education interaction on two tests. The interaction indicates that gender difference in test scores was much smaller in participants with more education than those who had less or no education. These demographically adjusted, regression-based norms can be a useful tool to clinicians involved with differential diagnosis of cognitive and memory disorders in older adults in rural China.

Correlates of depressive symptoms in rural elderly Chinese

OBJECTIVE

Late life depression has been studied in many populations around the world. However, findings on risk factors for late life depression have remained inconsistent.

METHODS

A cross-sectional survey of 1737 rural Chinese age 65 and over from two provinces in China was conducted assessing cognitive functions using various cognitive instruments and collecting information on demographic characteristics and medical history. Depressive symptoms were assessed using the Geriatric Depression Scale (GDS). Analysis of covariance and logistic regression models were used to identify factors associated with the continuous GDS score, mild or severe depression.

RESULTS

In this cohort, 26.5% (95% CI: 24.4-28.6%) met the criteria for mild depression and 4.3% (95% CI: 3.4-5.4%) for severely depression. Living alone, history of heart attack, head injury, and fracture were associated with higher depressive symptoms. Alcohol consumption and higher cognitive function were associated with lower depressive symptoms. Living alone, not attended school, history of head injury, fracture, and low cognitive function were associated with increased probability of mild depression. Living alone, history of stroke or heart attack, and low cognitive function were associated with severe depression.

CONCLUSIONS

Depression, particularly mild depression, is common in rural elderly Chinese. Among a number of factors identified in this cohort as being significantly associated with depressive symptoms, living alone and lower cognitive function were the most consistent factors associated with depressive symptoms, mild and severe depression. History of stroke, heart attack, and fracture were also risk factors for depressive symptoms.

Hypertension and cognitive decline in rural elderly Chinese

OBJECTIVES

To examine the association between hypertension and cognitive decline in older adults.

DESIGN

Prospective observational study.

SETTING

Four rural counties in China.

PARTICIPANTS

Two thousand rural Chinese aged 65 and older (median age 70, range 65-92) participated in a baseline evaluation. A follow-up evaluation of 1,737 subjects was conducted 2.5 years after baseline.

MEASUREMENTS

Cognitive function was assessed using the Community Screening Instrument for Dementia (CSID), Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word List Learning and Recall Tests, Indiana University (IU) Story Recall Test, Animal Fluency Test, and IU Token Test. Hypertension was defined as the mean of two readings of systolic blood pressure (BP) of 140 mmHg or greater, diastolic BP of 90 mmHg or greater, or according to self-report. Cognitive decline was derived as the difference between baseline and follow-up scores. Analysis of covariance models were used to estimate the association between hypertension, BP, and cognitive decline, adjusting for other covariates.

RESULTS

Greater decline was found on the CERAD 10-Word List Learning (P<.001) and Recall (P=.01) scores for subjects with hypertension than for those without. In particular, significantly greater decline was seen in the group with hypertension that was not taking medication than in the group without hypertension. No significant difference on cognitive decline was found between subjects with hypertension who were taking medication and those without hypertension.

CONCLUSION

Untreated hypertension was associated with greater cognitive decline in this Chinese cohort. Better hypertension detection and treatment in elderly people, especially in developing countries, may offer protection against cognitive decline.

Trace element levels and cognitive function in rural elderly Chinese

BACKGROUND

Trace elements are involved in metabolic processes and oxidation-reduction reactions in the central nervous system and could have a possible effect on cognitive function. The relationship between trace elements measured in individual biological samples and cognitive function in an elderly population had not been investigated extensively.

METHODS

The participant population is part of a large cohort study of 2000 rural elderly Chinese persons. Six cognitive assessment tests were used to evaluate cognitive function in this population, and a composite score was created to represent global cognitive function. Trace element levels of aluminum, calcium, cadmium, copper, iron, lead, and zinc were analyzed in plasma samples of 188 individuals who were randomly selected and consented to donating fasting blood. Analysis of covariance models were used to assess the association between each trace element and the composite cognitive score adjusting for demographics, medical history of chronic diseases, and the apolipoprotein E (APOE) genotype.

RESULTS

Three trace elements-calcium, cadmium, and copper-were found to be significantly related to the composite cognitive score. Increasing plasma calcium level was associated with higher cognitive score (p <.0001). Increasing cadmium and copper, in contrast, were significantly associated with lower composite score (p =.0044 and p =.0121, respectively). Other trace elements did not show significant association with the composite cognitive score.

CONCLUSIONS

Our results suggest that calcium, cadmium, and copper may be associated with cognitive function in the elderly population.

Selenium level and cognitive function in rural elderly Chinese

Selenium is a trace element associated with antioxidant activity and is considered to be a protective agent against free radicals through enhanced enzyme activity. Studies on selenium and cognitive function or Alzheimer's disease have yielded inconsistent results. A cross-sectional survey of 2,000 rural Chinese aged 65 years or older from two provinces in the People's Republic of China was conducted from December 2003 to May 2005 by use of the Community Screening Instrument for Dementia, the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word List Learning Test, the Indiana University Story Recall Test, the Animal Fluency Test, and the Indiana University Token Test. Over 70% of the study participants have lived in the same village since birth. Nail samples were collected and analyzed for selenium contents. Analysis-of-covariance models were used to estimate the association between quintile selenium levels measured in nail samples and cognitive test scores, with adjustment for other covariates. Lower selenium levels measured in nail samples were significantly associated with lower cognitive scores (p < 0.0087 for all tests) except the Animal Fluency Test (p = 0.4378). A dose-response effect of selenium quintiles was also seen for those significant associations. Results in this geographically stable cohort support the hypothesis that a lifelong low selenium level is associated with lower cognitive function.

Trace element level in infant hair and diet, and in the local environment of the Moroccan city of Marrakech

A sample of 573 infants (aged 0 to 12 months) from the Moroccan city of Marrakech was studied in order to determine the level of Pb and Al contaminations. Mean values of Pb and Al in children's hair were 6.6 and 9.5 microg/l, respectively. Age, gender, and parents' occupation influenced significantly Pb content but not Al content. Larger mean values were measured for Al compared with Pb. This finding can be explained by a higher level of Al available in both the infant diet (complementary feeding) and the local environmental factors (soil and drinking water). During weaning, beverages like tea, widely used in Morocco, represent an important source of Pb and Al contamination. Al content in drinking water is above the international standard.

Lessons learned from international comparative crosscultural studies on dementia

International and crosscultural comparative studies of Alzheimer disease (AD) offer significant advantages in elucidating risk factors for the disease by providing a wider diversity of environmental exposures as well as greater genetic diversity than do studies confined to a single ethnic group in a developed country. They also present with major methodological problems. The problems and their possible solutions are discussed in this article by describing three projects involving the Cree and English-speaking residents of Manitoba, blacks from Indianapolis, Indiana, and Yoruba from Ibadan and residents of Chinese villages. In this review, the development and harmonization of a culture fair screening instrument for dementia, the CSID, is described. The advantage of a scientific paradigm that can incorporate genetic and environmental factors as well as their interactions to explore the etiology of AD is presented. The importance of developing strategies for recruitment and retention in international community-based studies is emphasized as is the necessity of establishing academic partnerships between the countries. The unique opportunity provided by geopolitical and sociocultural influences to study environmental exposures is exemplified by the ongoing study of the influence of selenium levels on cognition in Chinese villagers. Results from the Indianapolis, Indiana-Ibadan dementia project are presented suggesting that the incidence of AD is lower in Yoruba than in blacks and that this lower rate may be the result of a combination of genetic and environmental factors.

Cognitive impairment and composition of drinking water in women: findings of the EPIDOS Study

BACKGROUND

The concentration of aluminum or silica in drinking water may be a potential environmental risk factor for Alzheimer disease (AD).

OBJECTIVES

The objective was to investigate at baseline the potential association between the composition of drinking water and the level of cognitive function in women taking part in the Epidemiology of Osteoporosis (EPIDOS) Study and to determine during follow-up the effects of the composition of drinking water on the risk of AD.

DESIGN

Women aged >/=75 y (n = 7598) were recruited between 1992 and 1994 in 5 geographic areas of France. The participants from one center (n = 1462) were followed for </=7 y; during this time, an active search for incident cases of AD was conducted. The initial questionnaire comprised a food consumption survey with specific questions about the daily consumption of tap and mineral water. The evaluation of cognitive function was based on the Short Portable Mental Status Questionnaire. During follow-up, the diagnosis of dementia was made by a geriatrician and a neurologist.

RESULTS

A low silica concentration was associated with low cognitive performance at baseline. Compared with the nondemented subjects, the women with a diagnosis of AD during follow-up were older at inclusion, had a lower financial status and educational level, had a poorer perception of their own health, and had a more difficult time performing activities of daily living. A multivariate analysis including potential confounding factors showed that women with AD appeared to have been exposed to lower amounts of silica at baseline.

CONCLUSIONS

Silica in drinking water may reduce the risk of developing AD in elderly women. The results corroborate those of another epidemiologic study carried out in France. The potential effect of silica needs to be confirmed in additional investigations.

Aluminium as a risk factor in Alzheimer's disease, with emphasis on drinking water

Aluminium (Al) is clearly a powerful neurotoxicant. Considerable evidence exists that Al may play a role in the aetiology or pathogenesis of Alzheimer's disease (AD), but whether the link is causal is still open to debate. This paper reviews the epidemiological evidence linking Al and AD. Nine out of 13 published epidemiological studies of Al in drinking water and AD have shown statistically significant positive relations. Given the difficulty in producing high-quality data for the occurrence of AD and also for Al exposure, with the resulting unavoidable misclassification errors biasing any true association towards the null value, these studies are remarkably consistent. A major problem in their interpretation is that drinking water, even at high Al concentrations, only contributes a fraction of the total dietary intake of Al. In particular, regular consumers of antacids ingest gram amounts of Al daily, thousands of times the amounts taken in through drinking water, and epidemiological studies of antacid exposure and AD have been largely negative. However, Al is very poorly absorbed in the gastrointestinal tract, and the possibility that some Al fractions present in drinking water may be particularly bioavailable cannot be dismissed at present. The combined evidence linking Al and AD warrants substantial research efforts. Such efforts should focus on clarification of the cellular and molecular mechanisms in Al toxicity and of the basic metabolism and kinetics of Al in the human body, and on further epidemiological studies including diverse routes of Al exposure and also variables that are known or suspected to influence the individuals' susceptibility to AD, such as apolipoprotein E allele status and family history of AD.