Moderate Alcohol Use and Cognitive Function in the Guangzhou Biobank Cohort Study

Relation of cigarette smoking and alcohol drinking in midlife with risk of cognitive impairment in late life: the Singapore Chinese Health Study

Background

the relations of cigarette smoking and alcohol drinking with risk of cognitive impairment remain inconsistent.

Methods

to examine the independent and joint relations of smoking and alcohol drinking with cognitive impairment, we used data from 16,948 men and women, who had been followed-up for 16-23 (mean of 20) years as participants of the Singapore Chinese Health Study, a population-based prospective cohort. Data on smoking and alcohol drinking were collected at baseline (1993-98), when participants were aged 45-74 (mean 53) years. Cognition was assessed using a 30-item Mini-Mental State Examination during follow-up three visits (2014-16), when participants were aged 61-96 (mean 73) years. Multivariable logistic regression models were used to estimate the odd ratios (ORs) and 95% confidence intervals (CIs).

Results

cognitive impairment was present in 2,443 (14.4%) participants. Compared with non-current smokers, current smokers had 20% increased risk (OR = 1.20, 95% CI = 1.04-1.39). Compared with those who drank less than weekly, regular alcohol drinking (at least weekly) had 17% increased risk (OR = 1.17, 95% CI = 1.01-1.36). Compared with those who were neither smokers nor drinkers, those who were either current smokers or regular drinkers alone had no significantly increased risk, while the risk was highest in those who were both current smokers and regular drinkers (OR = 1.77, 95% CI = 1.39-2.26, Pinteraction = 0.003).

Conclusions

co-existence of smoking and regular alcohol drinking at midlife had a much stronger impact than the individual factors on risk of cognitive impairment in late life.

Genetically predicted 17beta-estradiol, cognitive function and depressive symptoms in women: A Mendelian randomization in the Guangzhou Biobank Cohort Study

OBJECTIVE

The role of estrogen in cognitive function and depressive symptoms is controversial due to discrepancies between results from randomized controlled trials (RCT) and observational studies. Mendelian randomization analysis may provide further insights concerning the role of estrogen in these outcomes as it assesses the effect of lifelong endogenous exposure but is less vulnerable to confounding than observational studies.

METHOD

We used separate sample instrumental variable analysis to estimate the association of log 17β estradiol with cognitive function (Delayed 10 word recall, and Mini Mental State Examination (MMSE)) and depressive symptoms (Geriatric Depression Scale (GDS)) in older Chinese women of the Guangzhou Biobank Cohort Study (GBCS, n=3086). The estimate was derived based on the Wald estimator, the ratio of the association of genetic determinants (rs1008805 and rs2175898) of log 17β-estradiol with cognitive function and depressive symptoms in GBCS and the association of log 17β-estradiol with genetic determinants in the sample of young women in Hong Kong (n=236).

RESULTS

Genetically predicted 17β-estradiol was not associated with delayed 10-word recall (0.42 words per log increase in 17β-estradiol (pmol/L), 95% confidence interval (CI) -0.49 to 1.34) MMSE (0.39 per log increase in 17β-estradiol (pmol/L), 95% CI -0.87 to 1.65) or GDS (0.24 per log increase in 17β-estradiol (pmol/L), 95% CI -0.57 to 1.05).

CONCLUSION

These results were largely consistent with evidence from RCTs and did not show any beneficial effect of estrogen on cognitive function and depressive symptoms. However, larger Mendelian randomization analyses are needed to identify any minor effects.

A study of mild cognitive impairment in veterans: role of hypertension and other confounding factors

INTRODUCTION

Hypertension has shown to be an important risk factor for the decline in cognitive function. Aim of our study is to investigate the presence of cognitive impairment of the elders with hypertension and other confounding factors.

METHODS

This study was conducted on 400 veterans who were matched one-to-one with the confounding factors for assessing the presence of mild cognitive impairment using both MMSE and Montreal Cognitive Assessment (MoCA). The 13 related factors of patient data were studied.

RESULTS

The prevalence rate of cognitive impairment was 29.25%. Age (OR 2.679, 95%CI 1.663-6.875), sleep impairment (OR 1.117, 95%CI 1.754-7.422), uncontrolled hypertension (OR 1.522, 95%CI 1.968-4.454), type 2 diabetes (OR 2.464, 95%CI 1.232-4.931), and hyperlipidaemia (OR 1.411, 95%CI 1.221-8.988) are the risk factors for the cognitive deterioration, while the protective factors are high level of education (OR 0.032, 95%CI 0.007-0.149) and regular exercise (OR 0.307, 95%CI 0.115-0.818).

DISCUSSION

Because some vascular disease risk factors, such as hypertension, can be treated effectively, cognitive decline related to these risk factors, and vascular disease per se, may be prevented or its course modified through more aggressive treatment and improved compliance.

The alcohol paradox: light-to-moderate alcohol consumption, cognitive function, and brain volume

BACKGROUND

Studies of older persons show consumption of light-to-moderate amounts of alcohol is positively associated with cognitive function and, separately, is negatively associated with total brain volume (TBV). This is paradoxical as generally, cognitive function is positively associated with TBV. We examined the relationships of TBV, global cognitive function (GCF), and alcohol consumption in a population-based cohort of 3,363 men and women (b. 1907-1935) participating in the Age Gene/Environment Susceptibility-Reykjavik Study (2002-2006) and who were free of dementia or mild cognitive impairment

METHODS

Drinking status (never, former, and current) and current amount of alcohol consumed were assessed by questionnaire. GCF is a composite score derived from a battery of cognitive tests. TBV, standardized to head size, is estimated quantitatively from brain magnetic resonance imaging.

RESULTS

Among women and not men, adjusting for demographic and cardiovascular risk factors, current drinkers had significantly higher GCF scores than abstainers and former drinkers (p < .0001); and GCF was associated with amount consumed. TBV was not associated with drinking status or amount consumed in men or women. GCF and TBV did significantly differ in their associations across alcohol categories (p interaction < .001). Within categories of alcohol intake, GCF and TBV were positively associated.

CONCLUSIONS

The difference in associations of alcohol intake to brain structure and function suggests there may be unmeasured factors that contribute to maintaining better GCF relative to TBV. However, at higher levels of reasonable alcohol consumption, there may be factors leading to reduced brain volume.

Epidemiologic studies of modifiable factors associated with cognition and dementia: systematic review and meta-analysis

Background

Cognitive impairment, including dementia, is a major health concern with the increasing aging population. Preventive measures to delay cognitive decline are of utmost importance. Alzheimer’s disease (AD) is the most frequent cause of dementia, increasing in prevalence from <1% below the age of 60 years to >40% above 85 years of age.

Methods

We systematically reviewed selected modifiable factors such as education, smoking, alcohol, physical activity, caffeine, antioxidants, homocysteine (Hcy), n-3 fatty acids that were studied in relation to various cognitive health outcomes, including incident AD. We searched MEDLINE for published literature (January 1990 through October 2012), including cross-sectional and cohort studies (sample sizes > 300). Analyses compared study finding consistency across factors, study designs and study-level characteristics. Selecting studies of incident AD, our meta-analysis estimated pooled risk ratios (RR), population attributable risk percent (PAR%) and assessed publication bias.

Results

In total, 247 studies were retrieved for systematic review. Consistency analysis for each risk factor suggested positive findings ranging from ~38.9% for caffeine to ~89% for physical activity. Education also had a significantly higher propensity for “a positive finding” compared to caffeine, smoking and antioxidant-related studies. Meta-analysis of 31 studies with incident AD yielded pooled RR for low education (RR = 1.99; 95% CI: 1.30-3.04), high Hcy (RR = 1.93; 95% CI: 1.50-2.49), and current/ever smoking status (RR = 1.37; 95% CI: 1.23-1.52) while indicating protective effects of higher physical activity and n-3 fatty acids. Estimated PAR% were particularly high for physical activity (PAR% = 31.9; 95% CI: 22.7-41.2) and smoking (PAR%=31.09%; 95% CI: 17.9-44.3). Overall, no significant publication bias was found.

Conclusions

Higher Hcy levels, lower educational attainment, and decreased physical activity were particularly strong predictors of incident AD. Further studies are needed to support other potential modifiable protective factors, such as caffeine.

Caffeine and alcohol intakes and overall nutrient adequacy are associated with longitudinal cognitive performance among U.S. adults

Among modifiable lifestyle factors, diet may affect cognitive health. Cross-sectional and longitudinal associations may exist between dietary exposures [e.g., caffeine (mg/d), alcohol (g/d), and nutrient adequacy] and cognitive performance and change over time. This was a prospective cohort study, the Baltimore Longitudinal Study of Aging (n = 628-1305 persons depending on the cognitive outcome; ∼2 visits/person). Outcomes included 10 cognitive scores, spanning various domains of cognition. Caffeine and alcohol intakes and a nutrient adequacy score (NAS) were estimated from 7-d food diaries. Among key findings, caffeine intake was associated with better baseline global cognition among participants with a baseline age (Agebase) of ≥70 y. A higher NAS was associated with better baseline global cognition performance (overall, women, Agebase <70 y), better baseline verbal memory (immediate and delayed recall, Agebase ≥70 y), and slower rate of decline or faster improvement in the attention domain (women). For an Agebase of <70 y, alcohol consumption was associated with slower improvement on letter fluency and global cognition over time. Conversely, for an Agebase of ≥70 y and among women, alcohol intake was related to better baseline attention and working memory. In sum, patterns of diet and cognition associations indicate stratum-specific associations by sex and baseline age. The general observed trend was that of putative beneficial effects of caffeine intake and nutrient adequacy on domains of global cognition, verbal memory, and attention, and mixed effects of alcohol on domains of letter fluency, attention, and working memory. Further longitudinal studies conducted on larger samples of adults are needed to determine whether dietary factors individually or in combination are modifiers of cognitive trajectories among adults.

Influence of Alzheimer's disease genes on cognitive decline: the Guangzhou Biobank Cohort Study

Cognitive decline is a reduction in cognitive ability usually associated with aging, and those with more extreme cognitive decline either have or are at risk of progressing to mild cognitive impairment and dementia including Alzheimer's disease (AD). We hypothesized that genetic variants predisposing to AD should be predictive of cognitive decline in elderly individuals. We selected 1325 subjects with extreme cognitive decline and 1083 well-matched control subjects from the Guangzhou Biobank Cohort Study in which more than 30,000 southern Chinese older people have been recruited and followed up. Thirty single-nucleotide polymorphisms in 29 AD-associated genes were genotyped. No statistically significant allelic associations with cognitive decline were found by individual variant analysis. At the level of genotypic association, we confirmed that the APOE ε4 homozygote significantly accelerated cognitive decline and found that carriers of the ACE rs1800764_C allele were more likely to show cognitive decline than noncarriers, particularly in those without college education. However, these effects do not survive after multiple testing corrections, and together they only explain 1.7% of the phenotypic variance in cognitive score change. This study suggests that AD risk variants and/or genes are not powerful predictors of cognitive decline in our Chinese sample.

Alcohol consumption and electrocardiographic left ventricular hypertrophy and mediation by elevated blood pressure in older Chinese men: the Guangzhou Biobank Cohort Study

BACKGROUND

Chinese people have a markedly lower alcohol consumption than people in the West. Whether alcohol consumption at such levels is associated with left ventricular hypertrophy, and the role of blood pressure (BP) in this relationship is unclear. We investigated the association between alcohol consumption and electrocardiographic left ventricular hypertrophy (ECG-LVH) and the mediating role of BP in Chinese men aged ≥50 years.

METHODS AND RESULTS

A case-control analysis was conducted on baseline cross-sectional data from the community-based Guangzhou Biobank Cohort Study (2003-2008), using standard 12-lead resting electrocardiograms. By comparing 191 new ECG-LVH cases with 4311 controls, excessive drinking (>210 g/week) showed excess risks for ECG-LVH (odds ratio [OR] = 1.90, 95% confidence interval [CI] = 1.12-3.24), after adjusting for education, income, occupation, physical activity, smoking, body mass index, fasting glucose, triglyceride, total cholesterol, high-density lipoprotein cholesterol, BP, and antihypertensive medication. Mediation analysis showed a significant mediating effect of BP on the association between excessive drinking and ECG-LVH: systolic (31%) and diastolic (16%). After multivariate adjustment, no significant association was found between occasional drinking (<once/week: OR = 1.20, 95% CI = 0.80-1.80) and moderate drinking (≥once/week to ≤210 g/week: OR = 0.88, 95% CI = 0.53-1.47) with increased/decreased risk of ECG-LVH.

CONCLUSIONS

Alcohol consumption at >210 g/week in Chinese men is an independent risk factor for ECG-LVH. Low power prevented us from examining whether drinking at <once/week to ≤210 g/week is associated with decreased/increased risk of ECG-LVH. Elevated BP partially mediates between alcohol and ECG-LVH. A Mendelian randomization approach with a large sample size is warranted to determine the relations among alcohol consumption, BP, and LVH.

Systematic differences among never, occasional and moderate alcohol users in southern China, and its use in alcohol research: a cross-sectional study

BACKGROUND

Western observational studies show moderate alcohol use, compared with never use, positively associated with health. Moderate users differ systematically from others, making these observations vulnerable to confounding. Observations from other contexts may help distinguish whether these associations are confounded. To assess whether southern Chinese would provide a more suitable setting to examine the association of moderate alcohol use with health, we compared never alcohol users with moderate alcohol users and occasional users in this setting.

METHODS

We used age-adjusted multinomial regression to assess sex-stratified associations of alcohol use (never, occasional (<1 occasion/week), moderate (≤140 g ethanol/week for women and ≤210 g for men)) with health attributes and indicators in the Guangzhou Biobank Cohort Study (2003-2008) (n=26 361).

RESULTS

Among men, moderate alcohol users, when compared with never users, had slightly lower socioeconomic position and unhealthier lifestyle. Conversely, occasional alcohol users, when compared with never users, had higher socioeconomic position and healthier lifestyle. Among women, when compared with never users, both occasional and moderate users had higher socioeconomic position and healthier lifestyle. However, all alcohol users for both sexes, when compared with never users, were more likely to be ever smokers and to be exposed to secondhand smoke.

CONCLUSIONS

Observations in alcohol epidemiology may be affected by confounding due to contextually specific systematic differences. Results from a particular setting should not be interpreted as causal unless they are verified in different populations and, preferably, in non-observational studies.

Is aldehyde dehydrogenase 2 a credible genetic instrument for alcohol use in Mendelian randomization analysis in Southern Chinese men?

BACKGROUND

Mendelian randomization studies provide a means of assessing causal relations without interventions, but require valid genetic instruments. We assessed the credibility of aldehyde dehydrogenase 2 (ALDH2) as a genetic instrument for alcohol use in Southern Chinese men.

METHODS

We genotyped the single nucleotide polymorphism rs671 of ALDH2 in 4867 men from the Guangzhou Biobank Cohort Study. We used linear regression to assess the strength of the association of ALDH2 variants with alcohol use, whether ALDH2 variants were independently associated with socio-economic position or other potential confounders and whether associations of ALDH2 variants with cardiovascular risk factors (systolic and diastolic blood pressure, HDL- and LDL-cholesterol, fasting glucose), triglycerides, body mass index, self reported cardiovascular disease, self-reported ischaemic heart disease, cognitive function (delayed 10-word recall and Mini Mental State Examination score) and liver function (alanine transaminase and aspartate transaminase) were fully mediated by alcohol use.

RESULTS

The minor allele frequency (A) of ALDH2 was 0.29. The F statistic for ALDH2 variants was 75.0, suggesting that substantial weak instrument bias is unlikely. ALDH2 variants were not associated with socio-economic position, smoking or physical activity. ALDH2 variants were only associated with diastolic blood pressure and HDL-cholesterol, but these genetic associations with blood pressure and HDL-cholesterol were attenuated after adjusting for alcohol use, suggesting the apparent genetic associations were possibly mediated by alcohol use.

CONCLUSIONS

ALDH2 variants are a credible genetic instrument for Mendelian randomization studies of alcohol use and many attributes of health in Southern Chinese men.

Evaluation of moderate alcohol use and cognitive function among men using a Mendelian randomization design in the Guangzhou biobank cohort study

Observational studies usually show that moderate alcohol use is associated with better cognitive function. Such studies are vulnerable to residual confounding arising from systematic differences between moderate alcohol users and others. A Mendelian randomization study carried out in a suitable population, such as southern Chinese men, in which alcohol use is low to moderate and is influenced by genotype, offers an alternative and superior approach for clarifying the causal effect of moderate alcohol use on cognitive function. The authors used aldehyde dehydrogenase 2 (ALDH2) genotype (AA, GA, or GG) as an instrumental variable in 2-stage least squares analysis to obtain unbiased estimates of the relation of alcohol consumption (measured in alcohol units (10 g ethanol) per day) with cognitive function, assessed from delayed 10-word recall score (n = 4,707) and Mini-Mental State Examination (MMSE) score (n = 2,284), among men from the Guangzhou Biobank Cohort Study (2003-2008). ALHD2 genotype was strongly associated with alcohol consumption, with an F statistic of 71.0 in 2-stage least squares analysis. Alcohol consumption was not associated with delayed 10-word recall score (-0.03 words per alcohol unit, 95% confidence interval: -0.18, 0.13) or MMSE score (0.06 points per alcohol unit, 95% confidence interval: -0.22, 0.34). Moderate alcohol use is unlikely to be cognitively protective.

Potential health benefits of moderate alcohol consumption: current perspectives in research

The benefits of moderate amounts of alcohol for a better health and longer life expectancy compared with abstinence have been suggested by the findings of numerous studies. However, controversies have emerged regarding the influence of confounding factors and the systematic errors that might have been inadvertently disregarded in the early studies. This review includes a description of the findings of those research studies published in the last 5 years on the effects of moderate alcohol consumption on all-cause mortality, CVD and inflammation, the immune system, insulin sensitivity, non-alcoholic fatty liver disease (NAFLD) and cancer. Promising evidences exist from both animal studies and human clinical trials regarding intermediate end-points of CHD and insulin sensitivity, such as HDL, adiponectin or fibrinogen. However, controversies and inconsistent findings exist regarding many of these diseases and related functions and biomarkers. Further research and human randomised-controlled trials with adequate standardisation of the study conditions are necessary in order to draw a comparison between studies, establish the causal effect of moderate alcohol intake on disease protection and reach consensus on the circumstances that allow the recommendation of moderate alcohol habitual intakes as a strategy for health maintenance.