Green tea and black tea consumption and prostate cancer risk: an exploratory meta-analysis of observational studies

Observational studies on tea consumption and prostate cancer (PCa) risk are still inconsistent. The authors conducted a meta-analysis to investigate the association between green tea and black tea consumption with PCa risk. Thirteen studies providing data on green tea or black tea consumption were identified by searching PubMed and ISI Web of Science databases and secondary referencing qualified for inclusion. A random-effects model was used to calculate the summary odds ratios (OR) and their corresponding 95% confidence intervals (CIs). For green tea, the summary OR of PCa indicated a borderline significant association in Asian populations for highest green tea consumption vs. non/lowest (OR = 0.62; 95% CI: 0.38-1.01); and the pooled estimate reached statistically significant level for case-control studies (OR = 0.43; 95% CI: 0.25-0.73), but not for prospective cohort studies (OR = 1.00; 95% CI: 0.66-1.53). For black tea, no statistically significant association was observed for the highest vs. non/lowest black tea consumption (OR = 0.99; 95% CI: 0.82-1.20). In conclusion, this meta-analysis supported that green tea but not black tea may have a protective effect on PCa, especially in Asian populations. Further research regarding green tea consumption across different regions apart from Asia is needed.     

Review: Green Tea Polyphenols in Chemoprevention of Prostate Cancer: Preclinical and Clinical Studies

The prevention of prostate cancer (PCa) is a crucial medical challenge in developed countries. PCa remains surrounded by puzzles in spite of the considerable progress in research, diagnosis, and treatment. It is an ideal target for chemoprevention, as clinically significant PCa usually requires more than two decades for development. Green tea and its major constituent epigallocatechin gallate (EGCG) have been extensively studied as a potential treatment for a variety of diseases including cancer. In this review, we highlight the evidences of green tea polyphenols from preclinical and clinical studies in the chemoprevention/chemotherapy of PCa.     

Whole Grain Consumption and Inflammatory Markers: A Systematic Literature Review of Randomized Control Trials

Whole grain foods are rich in nutrients, dietary fibre, a range of antioxidants, and phytochemicals, and may have potential to act in an anti-inflammatory manner, which could help impact chronic disease risk. This systematic literature review aimed to examine the specific effects of whole grains on selected inflammatory markers from human clinical trials in adults. As per the Preferred Reporting Items for Systematic Reviews (PRISMA) protocol, the online databases MEDLINE, Embase, Cochrane, CINAHL, and Scopus were searched from inception through to 31 August 2021. Randomized control trials (RCTs) ≥ 4 weeks in duration, reporting ≥1 of the following: C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor (TNF), were included. A total of 31 RCTs were included, of which 16 studies recruited overweight/obese individuals, 12 had pre-existing conditions, two were in a healthy population, and one study included participants with prostate cancer. Of these 31 RCTs, three included studies with two intervention arms. A total of 32 individual studies measured CRP (10/32 were significant), 18 individual studies measured IL-6 (2/18 were significant), and 13 individual studies measured TNF (5/13 were significant). Most often, the overweight/obese population and those with pre-existing conditions showed significant reductions in inflammatory markers, mainly CRP (34% of studies). Overall, consumption of whole grain foods had a significant effect in reducing at least one inflammatory marker as demonstrated in 12/31 RCTs.     

Green tea and gastric cancer risk: meta-analysis of epidemiologic studies

OBJECTIVE: To evaluate the association between green tea consumption and the risk of gastric cancer. METHODS: Electronic search of the Cochrane Library, MEDLINE, EMBASE and Chinese Bio-medicine Database, which have articles published between (1966 and 2006), was conducted to select studies for this meta-analysis. RESULTS: This meta-analysis included 14 epidemiologic studies, with a total number of 6123 gastric cancer cases and 134006 controls. The combined results based on all studies showed that green tea consumption was not associated with the risk of gastric cancer [odds ratio (OR)=0.98, 95% confidence interval (CI)=0.77-1.24]. The summary OR from all population-based case-control studies showed a minor inverse association between green tea consumption and risk of gastric cancer (OR=0.68, 95% CI=0.49-0.92), while no associations were noted from hospital-based case-control studies (OR=1.12, 95% CI=0.70-1.77) and cohort studies (OR=1.56, 95% CI=0.93-2.60). No associations were noted both in males (OR=1.10, 95% CI=0.76-1.60) and females (OR=0.99, 95% CI=0.64-1.51). The summary OR from seven studies suggest that the highest consumption level of green tea was more than 5 cups per day and no associations were noted (OR=0.99, 95% CI=0.78-1.27). CONCLUSIONS: The results of this meta-analysis indicated that there is no clear epidemiological evidence to support the suggestion that green tea plays a role in the prevention of gastric cancer.     

Prevention and control of neglected tropical diseases: overview of randomized trials,systematic reviews and meta-analyses

Objective

To analyse evidence from randomized controlled trials (RCTs) on the prevention and control of neglected tropical diseases (NTDs) and to identify areas where evidence is lacking.

Methods

The Cochrane Central Register of Controlled Trials and PubMed were searched for RCTs and the Cochrane Database of Systematic Reviews and PubMed were searched for meta-analyses and systematic reviews, both from inception to 31 December 2012.

Findings

Overall, 258 RCTs were found on American trypanosomiasis, Buruli ulcer, dengue, geohelminth infection, leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, rabies, schistosomiasis or trachoma. No RCTs were found on cysticercosis, dracunculiasis, echinococcosis, foodborne trematodes, or human African trypanosomiasis. The most studied diseases were geohelminth infection (51 RCTs) and leishmaniasis (46 RCTs). Vaccines, chemoprophylaxis and interventions targeting insect vectors were evaluated in 113, 99 and 39 RCTs, respectively. Few addressed how best to deliver preventive chemotherapy, such as the choice of dosing interval (10) or target population (4), the population coverage needed to reduce transmission (2) or the method of drug distribution (1). Thirty-one publications containing 32 systematic reviews (16 with and 16 without meta-analyses) were found on American trypanosomiasis, dengue, geohelminths, leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, schistosomiasis or trachoma. Together, they included only 79 of the 258 published RCTs (30.6%). Of 36 interventions assessed, 8 were judged effective in more than one review.

Conclusion

Few RCTs on the prevention or control of the principal NTDs were found. Trials on how best to deliver preventive chemotherapy were particularly rare.     

Clinical and cost-effectiveness of donepezil, rivastigmine and galantamine for Alzheimer's disease: a rapid and systematic review

BACKGROUND: Alzheimer's disease is the most common cause of dementia and is characterised by an insidious onset and slow deterioration. The estimated prevalence of Alzheimer's disease for a standard health authority (500,000 people) is about 3330. Current service involves a wide range of agencies, and drug therapy for some patients. OBJECTIVES: To provide a rapid and systematic review of the clinical effectiveness and cost-effectiveness of donepezil, rivastigmine and galantamine in the symptomatic treatment of people suffering from Alzheimer's disease. METHODS: A systematic review of the literature was undertaken. METHODS - DATA SOURCES: Searches were made of electronic databases, including MEDLINE, EMBASE, The Cochrane Library, Database of Abstracts of Reviews of Effectiveness, NHS Economic Evaluation Database, National Research Register, Science Citation Index, BIOSIS, EconLit, MRC Trials database, Early Warning System, Current Controlled Trials, TOXLINE, Index of Scientific and Technical Proceedings, and Getting Easier Access to Reviews. All sources were searched over the period covered by the databases up to March/July 2000. Bibliographies of related papers were assessed for relevant studies and experts were contacted for advice and peer review, and to identify additional published and unpublished references. Manufacturer submissions to the National Institute for Clinical Excellence (NICE) were reviewed. METHODS - STUDY SELECTION: Studies were included if they fulfilled the following criteria: (1) Intervention: donepezil, rivastigmine or galantamine used to treat Alzheimer's disease. (2) Participants: people diagnosed with Alzheimer's disease who meet the criteria for treatment with donepezil, rivastigmine and galantamine. (3) Outcomes: measures assessing changes in cognition, function, behaviour and mood, quality of life (including studies assessing carer well-being and carer-input), and time to institutionalisation. (4) Design: systematic reviews of randomised controlled trials (RCTs) and RCTs comparing donepezil, rivastigmine or galantamine with placebo or each other or non-drug comparators were included in the review of effectiveness. Economic studies of donepezil, rivastigmine or galantamine used to treat Alzheimer's disease that included a comparator (or placebo) and both the costs and consequence (outcomes) of treatment were included in the review of cost-effectiveness. Studies in non-English language, and abstracts and conference poster presentations of systematic reviews, RCTs and economic evaluations were excluded. Two reviewers identified studies by independently screening study titles and abstracts, and then by examining the full text of selected studies to decide inclusion. METHODS - DATA EXTRACTION AND QUALITY ASSESSMENT: Data extraction and quality assessment were undertaken by one reviewer and checked by a second reviewer, with any disagreements resolved through discussion. The quality of RCTs was assessed using the Jadad scale and the quality of systematic reviews was assessed using criteria developed by the NHS Centre for Reviews and Dissemination. The quality of economic evaluation studies was assessed by their internal validity (i.e. the methods used) using a standard checklist, and external validity (i.e. the generalisability of the economic study to the population of interest) using a series of relevant questions. METHODS - DATA SYNTHESIS: The clinical effectiveness and cost-effectiveness of donepezil, rivastigmine and galantamine were synthesised through a narrative review with full tabulation of results of all included studies. In the economic evaluation, the reviewers assessed whether adjustments could be made to existing models to reflect the current situation in England and Wales. RESULTS - CLINICAL EFFECTIVENESS: (1) Donepezil--three systematic reviews and five RCTs (plus four studies from industry (unpublished data, submitted as commercial in confidence)) were found. Results suggest that donepezil is beneficial when assessed using global and cognitive outcome measures. (2) Rivastigmine--three systematic reviews and five RCTs (plus two studies from industry (unpublished data, submitted as commercial in confidence)) were found. Results suggest that rivastigmine is beneficial in terms of global outcome measures. (3) Galantamine--one systematic review and three RCTs (plus three studies from industry (unpublished data, submitted as commercial in confidence)) were found. Results suggest that galantamine is beneficial in terms of global, cognitive and functional scales. RESULTS - SUMMARY OF BENEFITS: It is difficult to quantify benefits from the evidence available in the literature. Statistically significant improvements in tests such as ADAS-cog (Alzheimer's Disease Assessment Scale cognitive subscale) may not be reflected in changes in daily life. (ABSTRACT TRUNCATED)     

Green Tea Consumption and Risk of Esophageal Cancer: A Meta-Analysis of Published Epidemiological Studies

We performed a meta-analysis to analyze the association of various levels of green tea consumption with risk of esophageal cancer. We searched MEDLINE, EMBASE, and the Cochrane Library for studies of green tea consumption and esophageal cancer and identified 12 observational studies. For esophageal cancer, the pooled relative risk (RR) was 1.09 [95% confidence interval (CI), 0.76–1.55] for greatest vs. non/least green tea consumption; however, there was significant heterogeneity across studies (P = 0.00, I² = 75.5%). Compared with subjects who drank no/least green tea, the pooled RR was 1.14 (95% CI = 0.97–1.35) for moderate drinkers, 0.94 (95% CI = 0.77–1.13) for those who drank little, and 0.97 (95% CI = 0.77–1.22) for all subjects who had ever drunk green tea. Subgroup analysis showed that the RR was 0.46 (95% CI = 0.29–0.73) for female subjects. The results of the present meta-analysis are that any association between green tea and risk of esophageal cancer remains unclear. Subgroup analyses indicated that greater consumption of green tea might reduce the risk of esophageal cancer in female subjects. However, the results are based on limited research. Further research is needed to confirm the results and clarify the likely biological mechanisms.     

Tea and lycopene protect against prostate cancer

Prostate cancer is the most common male cancer in developed countries and is increasing in the developing world. Its long latency and geographical variation suggest the possibility of prevention or postponement of onset by dietary modification. To investigate the possible joint effect of lycopene and green tea on prostate cancer risk, a case-control study was conducted in Hangzhou, China, with 130 prostate cancer patients and 274 hospital controls. Information on tea and dietary intakes, and possible confounders was collected using a structured questionnaire. The risk of prostate cancer for the intake of tea and lycopene and their joint effect were assessed using multivariate logistic regression models. Prostate cancer risk was reduced with increased consumption of green tea. The protective effect of green tea was significant (odds ratio 0.14, 95% CI: 0.06-0.35) for the highest quartile relative to the lowest after adjusting for total vegetables and fruits intakes and other potential confounding factors. Intakes of vegetables and fruits rich in lycopene were also inversely associated with prostate cancer risk (odds ratio 0.18, 95% CI 0.08-0.39). Interaction analysis showed that the protective effect from tea and lycopene consumption was synergistic (p<0.01). This study suggests that habitual drinking tea and intakes of vegetables and fruits rich in lycopene could lead to a reduced risk of prostate cancer in Chinese men. Together they have a stronger preventive effect than either component taken separately. This is the first epidemiological study to investigate the joint effect between tea drinking and lycopene intake.     

Effect of Green Tea on Plasma Adiponectin Levels: A Systematic Review and Meta-analysis of Randomized Controlled Clinical Trials

Objective: Our objective was to perform a systematic review and meta-analysis on randomized controlled trials (RCTs) assessing the effect of green tea on serum adiponectin concentration.

Method: We searched PubMed, ISI Web of Science, Scopus, and the Google Scholar databases up to November 2016. RCTs conducted among human adults studied the effects of green tea and green tea extract on serum adiponectin concentrations as an outcome variable was included. The weighted mean differences and standard deviations (SD) of change in serum adiponectin levels were calculated. The random effects model was used for deriving a summary of mean estimates with their corresponding SDs. The protocol was registered with PROSPERO (No. CRD42017057716).

Result: Fourteen RCTs were eligible to be included in the systematic review and the meta-analysis. Our analysis showed that green tea did not significantly affect adiponectin concentrations in comparison with placebo (weighted mean difference = ?0.02 µg/ml, 95% confidence interval [CI], ?0.41, 0.38; p = 0.936). There was a substantial heterogeneity between studies (I² = 91.7%; p < 0.0001). Subgroup analyses based on sex, type of intervention, continent, and body mass index (BMI) could not explain the sources of heterogeneity. Metaregression analyses revealed that the dose and duration of green tea ingestion did not have any effect on adiponectin concentrations.

Conclusion: Green tea could not change the circulatory adiponectin levels. The dose and duration of green tea could not change the result. RCTs with longer follow-up periods and higher doses are needed to replicate our results.     

Converting systematic reviews to Cochrane format: a cross-sectional survey of Australian authors of systematic reviews

Background

Despite the growing reputation and subject coverage of the Cochrane Database of Systematic Reviews, many systematic reviews continue to be published solely in paper-based health care journals. This study was designed to determine why authors choose to publish their systematic reviews outside of the Cochrane Collaboration and if they might be interested in converting their reviews to Cochrane format for publication in the Cochrane Database of Systematic Reviews.

Methods

Cross-sectional survey of Australian primary authors of systematic reviews not published on the Cochrane Database of Systematic Reviews identified from the Database of Abstracts of Reviews of Effectiveness.

Results

We identified 88 systematic reviews from the Database of Abstracts of Reviews of Effectiveness with an Australian as the primary author. We surveyed 52 authors for whom valid contact information was available. The response rate was 88 per cent (46/52). Ten authors replied without completing the survey, leaving 36 valid surveys for analysis. The most frequently cited reasons for not undertaking a Cochrane review were: lack of time (78%), the need to undergo specific Cochrane training (46%), unwillingness to update reviews (36%), difficulties with the Cochrane process (26%) and the review topic already registered with the Cochrane Collaboration (21%). (Percentages based on completed responses to individual questions.) Nearly half the respondents would consider converting their review to Cochrane format. Dedicated time emerged as the most important factor in facilitating the potential conversion process. Other factors included navigating the Cochrane system, assistance with updating and financial support. Eighty-six per cent were willing to have their review converted to Cochrane format by another author.

Conclusion

Time required to complete a Cochrane review and the need for specific training are the primary reasons why some authors publish systematic reviews outside of the Cochrane Collaboration. Encouragingly, almost half of the authors would consider converting their review to Cochrane format. Based on the current number of reviews in the Database of Abstracts of Reviews of Effectiveness, this could result in more than 700 additional Cochrane reviews. Ways of supporting these authors and how to provide dedicated time to convert systematic reviews needs further consideration.

     

AHRQ series paper 4: assessing harms when comparing medical interventions: AHRQ and the effective health-care program

Comparative effectiveness reviews (CERs) are systematic reviews that evaluate evidence on alternative interventions to help clinicians, policy makers, and patients make informed treatment choices. Reviews should assess harms and benefits to provide balanced assessments of alternative interventions. Identifying important harms of treatment and quantifying the magnitude of any risks require CER authors to consider a broad range of data sources, including randomized controlled trials (RCTs) and observational studies. This may require evaluation of unpublished data in addition to published reports. Appropriate synthesis of harms data must also consider issues related to evaluation of rare or uncommon events, assessments of equivalence or noninferiority, and use of indirect comparisons. This article presents guidance for evaluating harms when conducting and reporting CERs. We include suggestions for prioritizing harms to be evaluated, use of terminology related to reporting of harms, selection of sources of evidence on harms, assessment of risk of bias (quality) of harms reporting, synthesis of evidence on harms, and reporting of evidence on harms.     

The Role of Diet in the Prevention of Diabetes among Women with Prior Gestational Diabetes: A Systematic Review of Intervention and Observational Studies

BackgroundWomen with prior gestational diabetes (GDM) have an increased lifetime risk of developing type 2 diabetes mellitus (T2DM). There are no up-to-date systematic reviews analyzing the relationship of diet with risk of developing T2DM following GDM.ObjectiveTo systematically review the evidence from intervention and observational studies on effects of dietary interventions and associations of dietary intake with T2DM outcomes in women with a GDM history.MethodsSix electronic databases were searched (Cumulative Index to Nursing and Allied Health Literature, Embase, Medline, Cochrane Central, Proquest, and Scopus) for articles published until May 2019. This review includes intervention and observational studies among women of any age with a history of GDM that reported on the effects of dietary interventions or association of dietary intake (energy, nutrients, foods, dietary patterns) with T2DM, impaired glucose tolerance, impaired fasting glucose, or prediabetes.ResultsThe systematic review identified five articles reporting results from four intervention studies, and seven articles reporting results from four observational studies. Findings from intervention studies indicated trends toward beneficial effects of a low-glycemic index diet, a low-carbohydrate diet, and a diet in line with general population dietary guidelines, but studies had unclear or high risk of bias. Findings from two cross-sectional and one prospective study indicated poorer diabetes outcomes for women with higher intakes of branched-chain amino acids, total and heme iron, and a diet relatively low in carbohydrates and high in animal fat and protein, and better outcomes among those consuming diets rich in fruit, vegetables, nuts, fish, and legumes, and low in red and processed meats and sugar-sweetened beverages, after adjustment for confounders, including body mass index.ConclusionsFindings from observational studies support current dietary guidelines for the prevention of T2DM. Further dietary intervention studies are needed to confirm whether or not dietary modification following a GDM pregnancy reduces women's risk of developing T2DM.     

Influenza vaccination for HIV-positive people: Systematic review and network meta-analysis

BackgroundPeople with Human Immunodeficiency Virus (HIV) are highly susceptible to influenza-related morbidity and mortality. In order to assess comparative efficacy of influenza vaccine strategies among HIV-positive people, we performed a systematic review and Bayesian network meta-analysis (NMA).MethodsIn this systematic review, we searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and CINAHL between 1946 and July 2015 for randomized controlled trials (RCTs) on influenza vaccines for HIV-positive adults reporting seroconversion or seroprotection outcomes. The NMAs were conducted within a Bayesian framework and logistic models were used for comparing the effect of the vaccine strategies on the two outcomes.ResultsA total of 1957 publications were identified, 143 were selected for full review, and 13 RCTs were included in our final analysis. Fourteen separate NMAs were conducted by outcomes, vaccine strain, and different outcome measurement timepoints. For example, compared with the 15 μg single vaccine strategy, the odds ratio was the highest for the adjuvant 7.5 μg booster strategy (2.99 [95% credible interval 1.18–7.66]) when comparing seroconversion for H1N1 at 14–41 days after the last dose of vaccination and for the 60 μg single strategy (2.33 [1.31–4.18]) when comparing seroconversion for strain B.ConclusionsThe adjuvant 7.5 μg booster and 60 μg single vaccine strategies provided better seroconversion and seroprotection outcomes. These findings have important implications for national and international guidelines for influenza vaccination for HIV-positive people and future research.     

The effectiveness of influenza vaccination in pregnancy in relation to child health outcomes: Systematic review and meta-analysis

ObjectivesTo determine the effectiveness of influenza vaccination during pregnancy on child health outcomes.DesignSystematic review/meta-analysis.Data sourcesClinical Trials.gov, Cochrane Library, EMBASE, Medline, Medline in process, PubMed and Web of Science, from 1st January 1996 to 29th June 2018. An updated Medline search was performed 30th June 2018 to 31st October 2019.MethodsRandomised controlled trials (RCTs) and observational studies reporting health outcomes of infants and children born to women who received inactivated influenza vaccine during pregnancy. The primary outcome was infant laboratory confirmed influenza (LCI). Secondary outcomes included influenza-like illness (ILI), other respiratory illnesses, primary care, clinic visit or hospitalisations due to influenza illness and long-term respiratory childhood outcomes.Results19 studies were included; 15 observational studies and 4 primary RCTs with an additional 3 papers reporting secondary outcomes of these RCTs. In a random effects meta-analysis of 2 RCTs including 5742 participants, maternal influenza vaccination was associated with an overall reduction of LCI in infants of 34% (95% confidence interval 15–50%). However, there was no effect of maternal influenza vaccination on ILI in infants ≤6 months old. Two RCTs were excluded from the meta-analysis for the outcome of LCI in infants (different controls used). Both of these studies showed a protective effect for infants from LCI, with a vaccine efficacy of up to 70%.Overall observational studies showed an inverse (protective) association between maternal influenza vaccination and infant LCI, hospitalisation and clinic visits due to LCI or ILI in infants and other respiratory illness in infants ≤6 months old.ConclusionsThis systematic review supports maternal influenza vaccination as a strategy to reduce LCI and influenza-related hospitalisations in young infants. Communicating these benefits to pregnant women may support their decision to accept influenza vaccination in pregnancy and increase vaccine coverage in pregnant women.RegistrationPROSPERO CRD42018102776.     

Tea Consumption and Epithelial Ovarian Cancer Risk: A Systematic Review of Observational Studies

Ovarian cancer is the seventh most common type of cancer in the United States and is often not diagnosed until late stages. Thus, identifying potential risk factors and prevention strategies is particularly important. This systematic review analyzes existing evidence on the association between tea consumption and epithelial ovarian cancer risk in human observational studies. PubMed was searched through September 30, 2010 for eligible articles; 16 articles met the inclusion criteria for this systematic review. Five studies found overall tea intake to be associated with a decreased epithelial ovarian cancer risk, 1 found a borderline decreased risk, 9 found no association, and 1 found a borderline increased risk. Overall, it does not appear that tea consumption increases risk of ovarian cancer, but there is insufficient evidence at this point to conclude that it is protective against ovarian cancer. Many of the studies included in this review had important limitations, especially related to the lack of detailed data collected on tea consumption. Further research is needed and should focus on more detailed assessment of type of tea consumed, frequency, and duration of tea intake. Future studies should also explore potential differences in the association between tea intake and ovarian cancer risk among subpopulations.     

Tea consumption and epithelial ovarian cancer risk: a systematic review of observational studies

Ovarian cancer is the seventh most common type of cancer in the United States and is often not diagnosed until late stages. Thus, identifying potential risk factors and prevention strategies is particularly important. This systematic review analyzes existing evidence on the association between tea consumption and epithelial ovarian cancer risk in human observational studies. PubMed was searched through September 30, 2010 for eligible articles; 16 articles met the inclusion criteria for this systematic review. Five studies found overall tea intake to be associated with a decreased epithelial ovarian cancer risk, 1 found a borderline decreased risk, 9 found no association, and 1 found a borderline increased risk. Overall, it does not appear that tea consumption increases risk of ovarian cancer, but there is insufficient evidence at this point to conclude that it is protective against ovarian cancer. Many of the studies included in this review had important limitations, especially related to the lack of detailed data collected on tea consumption. Further research is needed and should focus on more detailed assessment of type of tea consumed, frequency, and duration of tea intake. Future studies should also explore potential differences in the association between tea intake and ovarian cancer risk among subpopulations.     

Tea consumption and lung cancer risk: A meta-analysis of case–control and cohort studies

ObjectiveRecent epidemiologic studies, especially cohort and case–control studies, have yielded inconsistent findings regarding the association between tea consumption and risk for lung cancer. The aim of this study was to assess a potential relationship between tea consumption and the incidence of lung cancer worldwide.MethodsA systematic literature search of PubMed, Web of Science, the Cochrane Library, Google Scholar, the Chinese Biomedical Database, and Wanfang Database was conducted from 1966 to January 2014 by two investigators. All cohort studies and case–control studies that evaluated the association of tea and lung cancer were included. Summary relative risks (RR) and the corresponding 95% confidence intervals (CIs) were calculated using a random-effects model. Quality assessments were performed using the Newcastle–Ottawa Scale. Heterogeneity was assessed using the Q and I² tests, and the source of heterogeneity was detected by meta-regression analysis. Publication bias was evaluated with Egger's regression symmetry test. Subgroup analyses and sensitivity analysis were performed.ResultsThirty-eight lung cancer studies (26 case–control studies and 12 cohort studies) with 59,041 cases and 396,664 controls were included. Overall tea consumption was significantly associated with decreased risk for lung cancer (RR, 0.78; 95% CI, 0.70–0.87). Subgroup analyses showed that tea consumption was associated with reduced risk for lung cancer in women (RR, 0.76; 95% CI, 0.62–0.93), case–control studies (RR 0.72; 95% CI 0.63–0.83), Western studies (RR, 0.85; 95% CI, 0.75–0.97), and studies in China and Japan (RR, 0.74; 95% CI, 0.62–0.88). Both green tea (RR, 0.75; 95% CI, 0.62–0.91) and black tea (RR, 0.82; 95% CI, 0.71–0.94) were significantly associated with reduced lung cancer risk. No significant association was found in men or in cohort studies.ConclusionTea consumption may offer some protection against lung cancer.     

The practice of systematic reviews. XI. The Cochrane Library

Systematic reviews of the literature provide a summary of the current status of medical scientific research. They are important for the solution of medical questions by doctors active in clinical practice, may serve to support practice guidelines, and are used in health care to take policy decisions and to determine the research agenda. The Cochrane Library is the most important source of information on the efficacy of interventions in health care and comprises eight databases. The most relevant for doctors active in clinical practice are the Cochrane Database of Systematic Reviews, the Database of Abstracts of Reviews of Effects, and the Cochrane Central Register of Controlled Trials. At present, the first two databases contain over 5000 systematic reviews of the literature. The third database listed above is the largest database in the world with references to (randomised) controlled studies.     

New insights into the mechanisms of green tea catechins in the chemoprevention of prostate cancer

Prostate cancer is the most commonly diagnosed cancer and second most common cause of cancer deaths in American men. Its long latency, slow progression, and high incidence rate make prostate cancer ideal for targeted chemopreventative therapies. Therefore, chemoprevention studies and clinical trials are essential for reducing the burden of prostate cancer on society. Epidemiological studies suggest that tea consumption has protective effects against a variety of human cancers, including that of the prostate. Laboratory and clinical studies have demonstrated that green tea components, specifically the green tea catechin (GTC) epigallocatechin gallate, can induce apoptosis, suppress progression, and inhibit invasion and metastasis of prostate cancer. Multiple mechanisms are involved in the chemoprevention of prostate cancer with GTCs; understanding and refining models of fundamental molecular pathways by which GTCs modulate prostate carcinogenesis is essential to apply the utilization of green tea for the chemoprevention of prostate cancer in clinical settings. The objective of this article is to review and summarize the most current literature focusing on the major mechanisms of GTC chemopreventative action on prostate cancer from laboratory, in vitro, and in vivo studies, and clinical chemoprevention trials.