Tea consumption is associated with cognitive impairment in older Chinese adults

Does frequent tea consumption provide any benefit to cognitive function in older adults? Evidence from a national survey from China in 2018

Objectives

This present study aims to investigate the effect of tea consumption on cognitive function and examine possible psychosocial mechanisms in older adults.

Participants and methods

The data of this study came from the 2018 wave of the Chinese Longitudinal Healthy Longevity Survey(CLHLS), and a total of 11,910 valid samples were included. We used ordinary least squares (OLS) to explore whether frequent tea consumption had significant effect on the cognitive function of older people. The problem of endogeneity was addressed by using a propensity score matching (PSM). Then we further explored the psychosocial mechanisms of the effect using a stepwise regression approach.

Results

Frequent tea consumption produced a positive effect on Mini-Mental State Examination (MMSE) score (coefficient = 0.340, p < 0.01), and PSM showed similar results. Specifically, the positive effect of green tea (coefficient 0.409, p < 0.01) was significantly greater than the other teas (coefficient 0.261, p < 0.1). Moreover, frequent tea drinkers were 59.7, 74.8, and 81.8% less likely to have severe, moderate and mild cognitive impairment respectively, compared to infrequent tea drinkers (p < 0.01). Levels of depression and sleep quality had partial mediation effect for frequent tea consumption on cognitive function, accounting for 27.6 and 3.5% of the total effect, respectively.

Conclusion

Frequent tea consumption was found to have beneficial effects on cognitive function, especially in older people with green tea intake. Sleep quality and levels of depression partially mediated the association between frequent tea consumption and cognitive function among Chinese older adults.

Synthetic and Natural Bioactive Molecules in Balancing the Crosstalk among Common Signaling Pathways in Alzheimer's Disease: Understanding the Neurotoxic Mechanisms for Therapeutic Intervention

The structure and function of the brain greatly rely on different signaling pathways. The wide variety of biological processes, including neurogenesis, axonal remodeling, the development and maintenance of pre- and postsynaptic terminals, and excitatory synaptic transmission, depends on combined actions of these molecular pathways. From that point of view, it is important to investigate signaling pathways and their crosstalk in order to better understand the formation of toxic proteins during neurodegeneration. With recent discoveries, it is established that the modulation of several pathological events in Alzheimer's disease (AD) due to the mammalian target of rapamycin (mTOR), Wnt signaling, 5'-adenosine monophosphate activated protein kinase (AMPK), peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α), and sirtuin 1 (Sirt1, silent mating-type information regulator 2 homologue 1) are central to the key findings. These include decreased amyloid formation and inflammation, mitochondrial dynamics control, and enhanced neural stability. This review intends to emphasize the importance of these signaling pathways, which collectively determine the fate of neurons in AD in several ways. This review will also focus on the role of novel synthetic and natural bioactive molecules in balancing the intricate crosstalk among different pathways in order to prolong the longevity of AD patients.

Association between tea drinking and disability levels in older Chinese adults: a longitudinal analysis

Objective

As the global population ages, disability among the elderly presents unprecedented challenges for healthcare systems. However, limited research has examined whether dietary interventions like tea consumption may alleviate and prevent disability in older adults. As an important dietary therapy, the health benefits of tea drinking have gained recognition across research disciplines. Therefore, this study aimed to investigate the association between tea drinking habits and disability levels in the elderly Chinese population.

Methods

Leveraging data from the 2008 to 2018 waves of the Chinese Longitudinal Healthy Longevity Survey, we disaggregated tea drinking frequency and activities of daily living (ADL) measures and deployed fixed-effect ordered logit models to examine the tea-disability association for the first time. We statistically adjusted for potential confounders and conducted stratified analyses to assess heterogeneity across subpopulations.

Results

Multivariable fixed-effect ordered logistic regression suggested tea drinking has protective effects against ADL disability. However, only daily tea drinking was associated with lower risks of basic activities of daily living (BADL) disability [odds ratio (OR) = 0.61; 95% confidence interval (CI), 0.41-0.92] and lower levels of instrumental activities of daily living (IADL) disability (OR = 0.78; 95% CI, 0.64-0.95). Stratified analyses indicated heterogeneous effects across age and income groups. Daily tea drinking protected against BADL (OR = 0.26 and OR = 0.28) and IADL disability (OR = 0.48 and OR = 0.45) for adults over 83 years old and high-income households, respectively.

Conclusion

We found that drinking tea almost daily was protective against disability in elderly people, warranting further research into optimal dosages. Future studies should utilize more rigorous causal inference methods and control for confounders.

Natural Bioactive Products as Epigenetic Modulators for Treating Neurodegenerative Disorders

Neurodegenerative disorders (NDDs) are major health issues in Western countries. Despite significant efforts, no effective therapeutics for NDDs exist. Several drugs that target epigenetic mechanisms (epidrugs) have been recently developed for the treatment of NDDs, and several of these are currently being tested in clinical trials. Furthermore, various bioproducts have shown important biological effects for the potential prevention and treatment of these disorders. Here, we review the use of natural products as epidrugs to treat NDDs in order to explore the epigenetic effects and benefits of functional foods and natural bioproducts on neurodegeneration.

Can habitual tea drinking be an effective approach against age-related neurodegenerative cognitive disorders: A systematic review and meta-analysis of epidemiological evidence

Our present knowledge about the efficacy of tea consumption in improving age-related cognitive disorders is incomplete since previous epidemiological studies provide inconsistent evidence. This unified systematic review and meta-analysis based on updated epidemiological cohort studies and randomized controlled trials (RCTs) evidence aimed to overcome the limitations of previous reviews by examining the efficacy of distinct types of tea consumption. PubMed, Embase, and MEDLINE were searched up to May 20, 2022, and 23 cohorts and 12 cross-sectional studies were included. Random-effects meta-analyses were conducted to obtain pooled RRs or mean differences with 95% CIs. The pooled RRs of the highest versus lowest tea consumption categories were 0.81 (95% CIs: 0.75-0.88) and 0.69 (95% CIs: 0.61-0.77), respectively. The pooled mean difference of four included RCTs revealed a beneficial effect of tea on cognitive dysfunction (MMSE ES: 1.03; 95% CI, 0.14-1.92). Subgroup analyses further demonstrated that green and black tea intake was associated with a lower risk of cognitive disorders in eastern countries, especially in women. The evidence quality was generally low to moderate. The present review provides insight into whether habitual tea consumption can be an effective approach against age-related neurodegenerative cognitive disorders and summarizes potential mechanisms based on currently published literature.

Therapeutic Effects of Green Tea Polyphenol (‒)-Epigallocatechin-3-Gallate (EGCG) in Relation to Molecular Pathways Controlling Inflammation, Oxidative Stress, and Apoptosis

(‒)-Epigallocatechin-3-gallate (EGCG) is the most abundant polyphenol in green tea. Thanks to multiple interactions with cell surface receptors, intracellular signaling pathways, and nuclear transcription factors, EGCG possesses a wide variety of anti-inflammatory, antioxidant, antifibrotic, anti-remodelation, and tissue-protective properties which may be useful in the treatment of various diseases, particularly in cancer, and neurological, cardiovascular, respiratory, and metabolic disorders. This article reviews current information on the biological effects of EGCG in the above-mentioned disorders in relation to molecular pathways controlling inflammation, oxidative stress, and cell apoptosis.

Path Analysis Reveals the Direct Effect of PCB28 Exposure on Cognitive Dysfunction in Older Chinese Females

Background: Research indicates that exposure to polychlorinated biphenyls (PCBs) can cause neurobehavioral impairments in neonates and adults, but the way specific PCBs’ congeners impact cognition functions at a low exposure level in a real-life co-exposure system remains poorly understood. This study aimed to investigate the association of PCBs burden with cognition function among elderly adults. Methods: Based on the Weitang Geriatric Diseases study (2014−2015), the current study measured the plasma concentrations of six indicator-PCBs by GC-MS/MS and assessed the cognitive dysfunction (CoD) via an Abbreviated Mental Test in 266 participants (ages 61−90). Sequential logistic regression was used to analyze the effects of PCBs on cognition functions. Female participants aged less than or equal to 80 years were selected, and path analysis was used to determine the direct or indirect impacts of co-exposure PCBs on CoD by structural equation modeling. Results: After sequential adjustments to potential confounding factors and correction by the Bonferroni, no statistically significant correlation between PCBs exposure and CoD was found in participants (p > 0.05). However, in the co-exposure system, after controlling for co-exposures and confounders, exposure to PCB28 had a direct effect on CoD in females aged between 61 and 80, with a factor load of 0.670. Conclusions: After adjusting for the co-exposures and confounders, exposure to PCB28 can directly increase the risk of cognitive impairment in older Chinese females.

A comprehensive review on the prevention and regulation of Alzheimer's disease by tea and its active ingredients

Alzheimer's disease (AD) has brought a heavy burden to society as a representative neurodegenerative disease. The etiology of AD combines multiple factors, concluding family, gender, head trauma, diseases and social psychology. There are multiple hypotheses explaining the pathogenesis of AD such as β-amyloid (Aβ) deposition and tau hyperphosphorylation, which lead to extracellular amyloid plaques and neurofibrillary tangles in neurons. The existing therapeutic drugs have several disadvantages including single target, poor curative effect, and obvious side effects. Tea contains many bioactive components, such as tea polyphenols (TPP), L-theanine (L-TH), tea pigment, tea polysaccharides and caffeine. The epidemiological investigations have shown that drinking tea can reduce the risk of AD. The mechanisms of tea active ingredients in the prevention and regulation of AD includes reducing the generation and aggregation of Aβ; inhibiting tau aggregation and hyperphosphorylation; inhibiting neuronal apoptosis and regulate neurotransmitters; relieving oxidative stress and neuroinflammation as well as the regulation of intestinal flora. This review summarizes the different signaling pathways that tea active ingredients regulate AD. Furthermore, we propose the main limitations of current research and future research directions, hoping to contribute to the development of natural functional foods based on tea active ingredients in the prevention and treatment of AD.

Habitual tea consumption and 5-year incident metabolic syndrome among older adults: a community-based cohort study

Background

The effect of tea consumption on metabolic syndrome (MetS) remains controversial. The objective of this study is to examine the prospective association of tea consumption with 5-year incident MetS among aged population in China.

Methods

This analysis included 3005 Chinese adults aged 60 years or older who were free of MetS at baseline examination. MetS was defined according to the National Cholesterol Education Program-Adult Treatment Panel III. Information regarding tea consumption was collected via an interviewer-administrated questionnaire. The prospective associations between tea consumption at baseline and 5-year incident MetS, as well as its individual components, were assessed by multiple logistic regression models.

Results

Of the 3005 participants free of MetS at baseline, 406 participants (cumulative incidence: 13.5%) developed MetS at the 5-year follow-up examination. In multiple logistic regressions, 5-year cumulative incidence of MetS was found to be higher in those who drank tea more than 5 times per week as compared with non-habitual drinkers (OR = 1.38, 95% CI: 1.05-1.82; P = 0.02). This relationship still existed in men (OR = 1.43, 95%CI: 1.00-2.01; P = 0.05) when stratified by gender. Among the five major components of MetS, low high-density lipoprotein cholesterol was observed in men, while high body mass index, elevated blood pressure and the presence of diabetes mellitus were significant in women.

Conclusions

High-frequent tea consumption increased the risk of MetS among older Chinese adults. These findings may add novel knowledge to the current studies regarding the controversial effect of tea consumption on cardiovascular and metabolic health among the aged population.

Cognitive Impairment and Associated Factors in Rural Elderly in North China

BACKGROUND

China has the largest population living with dementia globally and urban-rural differences are significant in prevalence, risk factors, and health resources. Epidemiologic studies on cognitive impairment in rural areas are limited in China and other low- and middle-income countries.

OBJECTIVE

This study investigated cognitive impairment and associated factors in rural elderly aged 65 years and over in China.

METHODS

In total, 1,250 participants from ten villages in North China were recruited from June to September, 2017. Face-to-face structured interviews were conducted for data collection. The interviews included socio-demographic information, health status, and psychological assessments. Cognitive function was assessed using the Chinese version of the Mini-Mental State Examination. A multivariate logistic regression model with backward method was employed to identify factors associated with cognitive impairment.

RESULTS

The positive rate of cognitive impairment among rural Chinese elderly aged 65 years and older was 42.9% (95% CI, 40.1-45.6). No significant differences were found in cognitive impairment by age or gender before the age of 75 years. Older age, lack of formal school education, reliance on the basic living allowance as the only income source, poor hearing and vision function, diabetes, and activities of daily living dependence were associated with higher rate of cognitive impairment, while tea consumption and fatty liver disease were associated with lower cognitive impairment rate.

CONCLUSION

A very high percentage of rural elderly in China had cognitive impairment. Education programs and prevention interventions targeting modifiable risk factors among high-risk populations should be developed through collective efforts involving all stakeholders.

Current Quest in Natural Bioactive Compounds for Alzheimer's Disease: Multi-Targeted-Designed-Ligand Based Approach with Preclinical and Clinical Based Evidence

Alzheimer's disease is a common and most chronic neurological disorder (NDs) associated with cognitive dysfunction. Pathologically, Alzheimer's disease (AD) is characterized by the presence of β-amyloid (Aβ) plaques, hyper-phosphorylated tau proteins, and neurofibrillary tangles, however, persistence oxidative-nitrative stress, endoplasmic reticulum stress, mitochondrial dysfunction, inflammatory cytokines, pro-apoptotic proteins along with altered neurotransmitters level are common etiological attributes in its pathogenesis. Rivastigmine, memantine, galantamine, and donepezil are FDA approved drugs for symptomatic management of AD, whereas tacrine has been withdrawn because of hepatotoxic profile. These approved drugs only exert symptomatic relief and exhibit poor patient compliance. In the current scenario, the number of published evidence shows the neuroprotective potential of naturally occurring bioactive molecules via their antioxidant, anti-inflammatory, antiapoptotic and neurotransmitter modulatory properties. Despite their potent therapeutic implications, concerns have arisen in context to their efficacy and probable clinical outcome. Thus, to overcome these glitches, many heterocyclic and cyclic hydrocarbon compounds inspired by natural sources have been synthesized and showed improved therapeutic activity. Computational studies (molecular docking) have been used to predict the binding affinity of these natural bioactive as well as synthetic compounds derived from natural sources for the acetylcholine esterase, α/β secretase Nuclear Factor kappa- light-chain-enhancer of activated B cells (NF-kB), Nuclear factor erythroid 2-related factor 2(Nrf2) and other neurological targets. Thus, in this review, we have discussed the molecular etiology of AD, focused on the pharmacotherapeutics of natural products, chemical and pharmacological aspects and multi-targeted designed ligands (MTDLs) of synthetic and semisynthetic molecules derived from the natural sources along with some important on-going clinical trials.

Tea consumption and serum uric acid levels among older adults in three large-scale population-based studies in China

Background and aims

The association between serum uric acid (SUA) and tea consumption has been studied in previous work, and there were arguments among various population group employed as well as different statistical approaches. The aim of this work is to investigate the tea effect on SUA levels among older adults by comparing three large-scale populations with both cross-sectional and longitudinal analyses.

Method

We examined the relationship between intake and SUA levels among older adults using linear regression. All the studies include the parameters SUA levels, tea intake, age, sex, education level, smoking status, alcohol drinking status, body mass index (BMI), and health history (diabetes, hypertension, and fasting plasma glucose). The cross-sectional analyses were conducted with 4579 older adults in the Weitang Geriatric Diseases Study (WGDS, ≥60 years), 2440 in the China Health and Nutrition Survey (CHNS, ≥60 years) and 1236 in the Chinese Longitudinal Healthy Longevity Survey (CLHLS, ≥62 years); and the longitudinal analyses were performed with 3870 (84.5%) in the WGDS and 420 (34.0%) in the CLHLS. Multivariable linear regression analyses were performed in both cross-sectional and longitudinal studies.

Results

Cross-sectional studies showed that tea consumers tended to have higher SUA levels than non-tea consumers in all the three datasets (P < 0.05). However, longitudinal associations of SUA levels with tea consumption had no statistical significance (P>0.05). The results of sex-stratified analyses were consistent with those of the whole datasets.

Conclusions

This work implied that any possible association between tea consumption and SUA levels could be very weak.

Nutraceuticals and their Derived Nano-formulations for the Prevention and Treatment of Alzheimer's disease

Alzheimer's disease is one of the common chronic neurological disorders and associated with cognitive dysfunction, depression and progressive dementia. Presence of β-amyloid or senile plaques, hyper-phosphorylated tau proteins, neurofibrillary tangle, oxidative-nitrative stress, mitochondrial dysfunction, endoplasmic reticulum stress, neuroinflammation and derailed neurotransmitter status are the hallmark of AD. Currently, donepezil, memantine, rivastigmine and galantamine are approved by the FDA for symptomatic management. It is well-known that these approved drugs only exert symptomatic relief and possess poor patient-compliance. Additionally, various published evidence shows the neuroprotective potential of various nutraceuticals via their antioxidant, anti-inflammatory and anti-apoptotic effects in the preclinical and clinical studies. These nutraceuticals possess a significant neuroprotective potential and hence, can be a future pharmacotherapeutic for the management and treatment of AD. However, nutraceutical suffers from certain major limitations such as poor solubility, low bioavailability, low stability, fast hepatic-metabolism and larger particle size. These pharmacokinetic attributes restrict their entry into the brain via the blood-brain barrier. Therefore, to over such issues, various nanoformulation of nutraceuticals was developed, that allows their effective delivery into brain owning to reduced particle size, increased lipophilicity increased bioavailability and avoidance of fast hepatic metabolism. Thus, in this review, we have discussed the etiology of AD, focused on the pharmacotherapeutics of nutraceuticals with preclinical and clinical evidence, discussed pharmaceutical limitation and regulatory aspects of nutraceuticals to ensure safety and efficacy. We further explored the latitude of various nanoformulation of nutraceuticals as a novel approach to overcome the existing pharmaceutical limitation and for effective delivery into the brain.

Leukocyte related parameters in older adults with metabolically healthy and unhealthy overweight or obesity

It remains unclear whether leukocyte-related parameters could be used as biomarkers to differentiate metabolically unhealthy overweight/obesity (MUO) from metabolically healthy overweight/obesity (MHO). We aimed to examine the differences in the distribution of leukocyte-related parameters between older adults with MHO and MUO and the correlations of leukocyte-related parameters with individual components of metabolic abnormality. In the Weitang Geriatric Diseases Study on older Chinese adults aged 60 years or above, 404 individuals with MHO and 480 with MUO contributed to the analysis. Overweight/obesity was defined as body mass index (BMI) of 25 kg/m² or more. MHO and MUO were discriminated based on the Adult Treatment Panel III (ATP III) criteria. Leukocyte-related parameters were assessed using an automated hematology analyzer. All leukocyte-related parameters except monocytes were elevated in MUO group compared with MHO group (all P < 0.05). The prevalence of MUO increased by 24% with each 10⁹/L increase of leukocytes after adjusting for confounders in the multiple-adjusted model (P < 0.01) and each unit elevation of other parameters except lymphocytes and monocytes were significantly associated with the presence of MUO (all P < 0.01). Trend tests revealed a linear trend for the association between MUO and all the leukocyte-related parameters (all P for trend < 0.05). Significant interactions between leukocyte-related parameters and sex on the presence of MUO were observed (all P value for interaction < 0.05). Higher leukocyte-related parameters were found in patients with MUO than those with MHO and were associated with higher prevalence of MUO which seems to be sex-dependent. Further studies are needed to see whether these parameters could be used as biomarkers for the screening or diagnosis for MUO in clinical or public health practice.

Longitudinal association between sleep and 5-year incident metabolic syndrome in older Chinese adults: a community-based cohort study

PURPOSE

Our aim was to investigate the association between sleep and the development of metabolic syndrome (MetS) in Chinese older adults and to accumulate evidence for the prevention of MetS through sleep management.

METHODS

This prospective study followed 3005 participants aged over 60 derived from the Weitang Geriatric Diseases Study who were without MetS at baseline. MetS was defined according to the Adult Treatment Panel III (ATP III) criteria. Logistic regression models were fit to assess the association between sleep and MetS incident and a linear regression model was used to examine the impact of sleep duration on every component of MetS. Data on sleep-related parameters were obtained based on a self-reported questionnaire.

RESULTS

After five-year follow-up, 13.51% participants developed MetS, of which 46.86% were women. The incidence of MetS was highest among adults who slept 6 h or less and lowest among those who slept 7 h after adjusted for multiple variables. Subgroup analyses showed no gender specificity. The variation of fasting plasma glucose (FBG) for ≥9 h per night was significantly lower than that for 7.01-7.99 h per night (β = -0.18, P < 0.05). Sleeping for 8-8.99 h also decreased the variation of diastolic blood pressure (DBP) compared to 7.01-7.99 h (β = -0.84, P < 0.05).

CONCLUSION

We conclude that both short and long sleep duration are risk factors for MetS incident in older adults.

Beneficial Effects of Epigallocatechin-3-O-Gallate, Chlorogenic Acid, Resveratrol, and Curcumin on Neurodegenerative Diseases

Many observational and clinical studies have shown that consumption of diets rich in plant polyphenols have beneficial effects on various diseases such as cancer, obesity, diabetes, cardiovascular diseases, and neurodegenerative diseases (NDDs). Animal and cellular studies have indicated that these polyphenolic compounds contribute to such effects. The representative polyphenols are epigallocatechin-3-O-gallate in tea, chlorogenic acids in coffee, resveratrol in wine, and curcumin in curry. The results of human studies have suggested the beneficial effects of consumption of these foods on NDDs including Alzheimer's and Parkinson's diseases, and cellular animal experiments have provided molecular basis to indicate contribution of these representative polyphenols to these effects. This article provides updated information on the effects of these foods and their polyphenols on NDDs with discussions on mechanistic aspects of their actions mainly based on the findings derived from basic experiments.

Combined effect of three common lifestyle factors on cognitive impairment among older Chinese adults: a community-based, cross-sectional survey

AIM

Lifestyle factors may influence cognitive function. Therefore, we compared the risk of cognitive impairment (COI) of all possible combinations of three lifestyle factors-tea consumption, physical activity, and siesta (afternoon nap or rest)-to the absence of any of these lifestyle factors.

METHODS

This cross-sectional study consisted of 4579 community-dwelling Chinese individuals aged 60 years or older living in Suzhou. Among the subjects were 3634 participants with normal cognition and 945 who had been diagnosed with COI according to the Abbreviated Mental Test. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated with a multivariate-adjusted model by logistic regression.

RESULTS

Individually, tea consumption and physical activity significantly lowered the risk of COI to 0.66 (95%CI: 0.48-0.90) and 0.79 (95%CI: 0.65-0.96), respectively. In combination, physical activity and siesta reduced the risk of COI to the greatest extent (OR = 0.44, 95%CI: 0.31-0.64). Based on multivariate adjustment, almost all combinations of factors had a significant negative association with COI, but the combination of tea consumption and siesta had an irrelevant correlation with COI. All combinations of lifestyle factors had a lower OR than any single lifestyle factor among the correlations that were significant.

CONCLUSION

Based on our findings, engaging in physical activity in combination with either or both of the other lifestyle factors was associated with a lower OR of having COI than adhering on a single factor in elderly Chinese people.

Associations between habitual tea consumption and 5-year longitudinal changes of systolic blood pressure in older Chinese

BACKGROUND AND OBJECTIVES

Tea consumption may contribute to the management of blood pressure; however, evidence from longitudinal studies is lacking. This study aimed to examine the relationship between habitual tea consumption and trajectories of systolic blood pressure in a community-based sample of Chinese adults aged 60 years or older.

METHODS

A prospective cohort of 3870 participants was investigated from 2014 to 2018. Trajectories of systolic blood pressure were identified using latent mixture modeling with the Proc Traj procedure. Multiple logistic regression models were fitted to explore associations between tea consumption habits and trajectories of systolic blood pressure.

RESULTS

In the overall sample, participants were less likely to be habitual tea drinkers if they were in the "moderate-stable" (144.4-149.9 mm Hg), "moderate-increasing" (157.2-180.0 mm Hg), and "elevated-increasing" (184.7-209.8 mm Hg) groups as compared to those in the "low-stable" group (125.3-130.0 mm Hg). The "elevated-decreasing" group (170.7 - 167.2 mmHg) consistently showed no significant difference in the likelihood of habitual tea drinking as compared to the "low-stable" group.

CONCLUSIONS

This community-based prospective study indicated that habitual tea consumption was associated with relatively favorable long-term systolic blood pressure statuses.

Does Green Tea Induce Hormesis?

Green tea, and its principal constituent (-)-epigallocatechin-3-gallate (EGCG), are commonly shown to induce biphasic concentration/dose responses in a broad range of cell types, including non-tumor cells, and tumor cell lines. The most active area of research dealt with an assessment of neural cells with application to neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease cell models, often using preconditioning experimental protocols. The general findings demonstrate EGCG-induced hormetic effects resulting in an enhanced acquired resilience within an adaptive and temporally dependent homeodynamic framework. The biphasic dose responses displayed the typical quantitative features of the hormetic dose response with respect to the amplitude and width of the stimulatory response. These findings provide further evidence for the general occurrence of hormetic dose responses with such responses being independent of the biological model, end point, inducing agent, and mechanism. The biphasic nature of these responses has important implications since it suggests optimal dose ranges for end points of public health and therapeutic applications. These findings indicate the need to assess the entire dose-response continuum in order to better define the nature of the dose response, especially in the low-dose zone where such exposures are common in human populations.

Gender Differences in Cognitive Impairment among Rural Elderly in China

Elders in rural areas of developing countries are particularly vulnerable to cognitive impairment and gender disparities are notable. Yet, evidence related to gender differences in cognitive impairment in these settings is scarce. This study examined gender differences in cognitive impairment among elderly people aged 65 and above in rural China. A multi-site cross-sectional survey was conducted. In total, 550 males and 700 females were recruited. The Chinese version of the Mini-Mental Status Examination was applied for cognitive impairment screening. Demographic information, lifestyle factors, psychosocial factors, and health-related information were assessed. The prevalence of cognitive impairment was 40.0%in males and 45.1% in females, respectively. Females showed significant higher prevalence after age 75 (62.7% vs. 45.4%, p < 0.005). Older age, hearing impairment, and activities of daily living dependence were common factors associated with cognitive impairment in both females and males. For males, living in a neighborhood with poor social interactions and diabetes were risk factors, while tea consumption was a protective factor. For females, vision impairment and illiteracy were additional risk factors. Individualized interventions and standardized measurements of cognitive function should be developed to suit older populations living in rural and less-developed areas, through collective efforts involving all stakeholders and multidisciplinary teamwork.

Neuroinflammation in pathogenesis of Alzheimer's disease: Phytochemicals as potential therapeutics

Accumulation of neurotoxic forms of amyloid-β proteins in senile plaques and hyperphosphorylated tau proteins in neurofibrillary tangles is a well-known pathophysiological hallmark of Alzheimer's disease (AD). However, clinical trials with drugs targeting amyloid-β and tau have failed to demonstrate efficacy in treating AD. All currently FDA-approved anti-AD drugs have symptomatic effects only and are not able to cure this disease. This makes necessary to search for alternative therapeutic targets. Accumulating evidence suggests that systemic inflammation and related vascular dysfunction play important etiological roles in AD and precede its clinical manifestation. Therefore, novel therapeutic modalities targeted at these pathophysiological components of AD are intensively developed now. Phytochemicals such as resveratrol, curcumin, quercetin, genistein and catechins are promising anti-AD therapeutics due to their ability to affect major pathogenetic mechanisms of AD, including oxidative stress, neuroinflammation and mitochondrial dysfunction. The implementation of innovative approaches for phytochemical delivery, including the nanotechnology-based ones which enable to significantly enhance their oral bioavailability, would likely provide an opportunity to address many challenges of conventional anti-AD therapies. In this review, roles of inflammation and vascular dysregulation in AD are described and phytobioactive compound-based treatment strategies for AD are discussed.

The Role of Dietary Antioxidants in the Pathogenesis of Neurodegenerative Diseases and Their Impact on Cerebral Oxidoreductive Balance

Neurodegenerative diseases are progressive diseases of the nervous system that lead to neuron loss or functional disorders. Neurodegenerative diseases require long-term, sometimes life-long pharmacological treatment, which increases the risk of adverse effects and a negative impact of pharmaceuticals on the patients’ general condition. One of the main problems related to the treatment of this type of condition is the limited ability to deliver drugs to the brain due to their poor solubility, low bioavailability, and the effects of the blood-brain barrier. Given the above, one of the main objectives of contemporary scientific research focuses on the prevention of neurodegenerative diseases. As disorders related to the competence of the antioxidative system are a marker in all diseases of this type, the primary prophylactics should entail the use of exogenous antioxidants, particularly ones that can be used over extended periods, regardless of the patient’s age, and that are easily available, e.g., as part of a diet or as diet supplements. The paper analyzes the significance of the oxidoreductive balance in the pathogenesis of neurodegenerative diseases. Based on information published globally in the last 10 years, an analysis is also provided with regard to the impact of exogenous antioxidants on brain functions with respect to the prevention of this type of diseases.

Associations Between Caffeine Consumption, Cognitive Decline, and Dementia: A Systematic Review

BACKGROUND

Epidemiologic studies have provided inconclusive evidence for a protective effect of caffeine consumption on risk of dementia and cognitive decline.

OBJECTIVE

To summarize literature on the association between caffeine and 1) the risk of dementia and/or cognitive decline, and 2) cognitive performance in individuals with mild cognitive impairment (MCI) or dementia, and 3) to examine the effect of study characteristics by categorizing studies based on caffeine source, quantity and other possible confounders.

METHODS

We performed a systematic review of caffeine effects by assessing overall study outcomes; positive, negative or no effect. Our literature search identified 61 eligible studies performed between 1990 and 2020.

RESULTS

For studies analyzing the association between caffeine and the risk of dementia and/or cognitive decline, 16/57 (28%) studies including a total of 40,707/153,070 (27%) subjects reported positive study outcomes, and 30/57 (53%) studies including 71,219/153,070 (47%) subjects showed positive results that were dependent on study characteristics. Caffeine effects were more often positive when consumed in moderate quantities (100-400 mg/d), consumed in coffee or green tea, and in women. Furthermore, four studies evaluated the relationship between caffeine consumption and cognitive function in cognitively impaired individuals and the majority (3/4 [75% ]) of studies including 272/289 subjects (94%) reported positive outcomes.

CONCLUSION

This review suggests that caffeine consumption, especially moderate quantities consumed through coffee or green tea and in women, may reduce the risk of dementia and cognitive decline, and may ameliorate cognitive decline in cognitively impaired individuals.

Associations of sleep durations and sleep-related parameters with metabolic syndrome among older Chinese adults

PURPOSE

There is a lack of data on the role of sleep in the development of metabolic syndrome (MetS) in older adults. We aimed to examine the associations of sleep durations at night and other sleep-related parameters with the presence of MetS in older Chinese adults.

METHODS

Data of 4579 individuals aged 60 years or older from the Weitang Geriatric Disease Study were analyzed. MetS was diagnosed based on the Adult Treatment Panel III (ATP III) criteria. Information regarding sleep durations and other sleep-related parameters was collected by questionnaires.

RESULTS

Compared with those with daytime napping, individuals without daytime napping were at an increased risk of MetS (odds ratio [OR] = 1.23; 95% confidence interval [CI] = 1.03-1.47). Each hour increase in daytime napping increased the risk of MetS by 33% (OR = 1.33; 95% CI = 1.15-1.52). After adjusting for the effect of age and gender, a J-shaped association between sleep durations at night and the presence of MetS was observed. The risk of MetS was lowest among those who slept 7-8 h at night. Gender-stratified analysis indicated that the J-shaped relationship between sleep durations at night and MetS remained significant in men but not in women.

CONCLUSIONS

In older Chinese adults, sleep durations at night might have a dual effect on the risk of MetS and this effect was particularly pronounced in men. The results indicated that circadian rhythm might play an important role in the development of MetS in older populations.

Function of Green Tea Catechins in the Brain: Epigallocatechin Gallate and its Metabolites

Over the last three decades, green tea has been studied for its beneficial effects, including anti-cancer, anti-obesity, anti-diabetes, anti-inflammatory, and neuroprotective effects. At present, a number of studies that have employed animal, human and cell cultures support the potential neuroprotective effects of green tea catechins against neurological disorders. However, the concentration of (−)-epigallocatechin gallate (EGCG) in systemic circulation is very low and EGCG disappears within several hours. EGCG undergoes microbial degradation in the small intestine and later in the large intestine, resulting in the formation of various microbial ring-fission metabolites which are detectable in the plasma and urine as free and conjugated forms. Recently, in vitro experiments suggested that EGCG and its metabolites could reach the brain parenchyma through the blood–brain barrier and induce neuritogenesis. These results suggest that metabolites of EGCG may play an important role, alongside the beneficial activities of EGCG, in reducing neurodegenerative diseases. In this review, we discuss the function of EGCG and its microbial ring-fission metabolites in the brain in suppressing brain dysfunction. Other possible actions of EGCG metabolites will also be discussed.

The Association between Green and Black Tea Consumption on Successful Aging: A Combined Analysis of the ATTICA and MEDiterranean ISlands (MEDIS) Epidemiological Studies

Tea is one of the most-widely consumed beverages in the world with a number of different beneficial health effects, mainly ascribed to the polyphenolic content of the tea catechins. The aim of this study was to examine the consumption of green, black, or no tea, in relation to the previously validated successful ageing index (SAI; higher values "healthier" ageing) in a combined analysis of adults aged >50 years old from the ATTICA (n = 1128 adults from Athens, Greece metropolitan area) and the MEDiterranean Islands Study (MEDIS) (n = 2221 adults from various Greek island and Mani) studies. After adjusting for age, sex, smoking, and coffee consumption, green tea was positively associated with SAI (b ± SE: 0.225 ± 0.055, p < 0.001), while black tea was negatively associated with SAI (unstandardized b coefficient ± Standard error: -0.807 ± 0.054, p < 0.001). Green tea (vs black tea) consumption, had higher odds of a SAI of over 3.58 out of 10 (OR: 1.77, 95% CI: 1.38-2.28). Green tea consumption was also associated with higher levels of physical activity (p < 0.001) and reduced likelihood of hypertension (p = 0.006) compared with black tea. Two possible mechanisms are that green tea possesses high levels of catechins such as (-)-epigallocatechin 3-gallate and l-theanine compared with black tea. Therefore, the present analysis supports both the role of green tea constituents in successful ageing, as well as its role as an important component of an overall healthy diet in adults aged 50 years and over from these two epidemiological studies.

Effects of Tea Catechins on Alzheimer's Disease: Recent Updates and Perspectives

Alzheimer’s disease (AD) is one of the most common neurodegenerative disorders worldwide. Its incidence is gradually increasing because of an aging demographic. Therefore, AD prevention and modification is important to improve the health status of older adults. Oxidative stress is a component of the pathological mechanisms underlying AD. It is caused by a disruption of the balance between reactive oxygen species and antioxidant molecules. This imbalance also causes neuroinflammation. Catechins, which are bioactive components of tea, have antioxidative and anti-inflammatory effects. Moreover, other potential properties related to AD prevention and modification have been reported in in vitro and in vivo studies. Several clinical studies have also been conducted to date. The current review summarizes recent updates and perspectives of the effects of catechins on AD based on the molecular mechanisms and related clinical studies.

Association of Tea Consumption with Risk of Alzheimer's Disease and Anti-Beta-Amyloid Effects of Tea

Neurodegenerative disease Alzheimer’s disease (AD) is attracting growing concern because of an increasing patient population among the elderly. Tea consumption is considered a natural complementary therapy for neurodegenerative diseases. In this paper, epidemiological studies on the association between tea consumption and the reduced risk of AD are reviewed and the anti-amyloid effects of related bioactivities in tea are summarized. Future challenges regarding the role of tea in preventing AD are also discussed.