Critical Appraisal of Epidemiological Studies and Clinical Trials

2017 ◽  
Author(s):  
Mark Elwood
Keyword(s):  
Cohort Studies ◽  
Statistical Methods ◽  
Critical Appraisal ◽  
Causal Effect ◽  
Internal Validity ◽  
Epidemiological Studies ◽  
Case Control ◽  
Randomised Trials ◽  
Case Control Studies ◽  
Retrospective Cohort Studies

This book presents a system of critical appraisal applicable to clinical, epidemiological and public health studies and to many other fields. It assumes no prior knowledge. The methods are relevant to students, practitioners and policymakers. The book shows how to assess if the results of one study or of many studies show a causal effect. The book discusses study designs: randomised and non-randomised trials, cohort studies, case-control studies, and surveys, showing the presentation of results including person-time and survival analysis, and issues in the selection of subjects. The system shows how to describe a study, how to detect and assess selection biases, observation bias, confounding, and chance variation, and how to assess internal validity and external validity (generalisability). Statistical methods are presented assuming no previous knowledge, and showing applications to each study design. Positive features of causation including strength, dose-response, and consistency are discussed. The book shows how to do systematic reviews and meta-analyses, and discusses publication bias. Systems of assessing all evidence are shown, leading to a general method of critical appraisal based on 20 key questions in five groups, which can be applied to any type of study or any topic. Six chapters show the application of this method to randomised trials, prospective and retrospective cohort studies, and case-control studies. An appendix summarises key statistical methods, each with a worked example. Each main chapter has self-test questions, with answers provided.

scholarly journals Dietary patterns and CVD: a systematic review and meta-analysis of observational studies

2015 ◽  
Vol 114 (9) ◽  
pp. 1341-1359 ◽  
Author(s):  
Míriam Rodríguez-Monforte ◽  
Gemma Flores-Mateo ◽  
Emília Sánchez
Keyword(s):  
Cohort Studies ◽  
Dietary Patterns ◽  
Observational Studies ◽  
Protective Factor ◽  
Meta Analysis ◽  
Epidemiological Studies ◽  
Case Control ◽  
Case Control Studies ◽  
Chd Risk ◽  
Control Comparison

AbstractEpidemiological studies show that diet is linked to the risk of developing CVD. The objective of this meta-analysis was to estimate the association between empirically derived dietary patterns and CVD. PubMed was searched for observational studies of data-driven dietary patterns that reported outcomes of cardiovascular events. The association between dietary patterns and CVD was estimated using a random-effects meta-analysis with 95 % CI. Totally, twenty-two observational studies met the inclusion criteria. The pooled relative risk (RR) for CVD, CHD and stroke in a comparison of the highest to the lowest category of prudent/healthy dietary patterns in cohort studies was 0·69 (95 % CI 0·60, 0·78; I2=0 %), 0·83 (95 % CI 0·75, 0·92; I2=44·6 %) and 0·86 (95 % CI 0·74, 1·01; I2=59·5 %), respectively. The pooled RR of CHD in a case–control comparison of the highest to the lowest category of prudent/healthy dietary patterns was 0·71 (95 % CI 0·63, 0·80; I2=0 %). The pooled RR for CVD, CHD and stroke in a comparison of the highest to the lowest category of western dietary patterns in cohort studies was 1·14 (95 % CI 0·92, 1·42; I2=56·9 %), 1·03 (95 % CI 0·90, 1·17; I2=59·4 %) and 1·05 (95 % CI 0·91, 1·22; I2=27·6 %), respectively; in case–control studies, there was evidence of increased CHD risk. Our results support the evidence of the prudent/healthy pattern as a protective factor for CVD.

scholarly journals Maternal Exposure to Alcohol and Low Birthweight: A Systematic Review and Meta-Analysis

2019 ◽  
Vol 41 (05) ◽  
pp. 333-347
Author(s):  
Priscilla Perez da Silva Pereira ◽  
Fabiana Araújo Figueiredo Da Mata ◽  
Ana Claudia Morais Godoy Figueiredo ◽  
Roberta Borges Silva ◽  
Maurício Gomes Pereira
Keyword(s):  
Systematic Review ◽  
Alcohol Consumption ◽  
Cohort Studies ◽  
Retrospective Cohort ◽  
Literature Search ◽  
Low Birthweight ◽  
Meta Analysis ◽  
Case Control ◽  
Case Control Studies ◽  
Retrospective Cohort Studies

Objective To investigate the relationship between maternal exposure to alcohol and low birthweight (LBW). Methods The literature search was performed in January 2017 using the following electronic databases: Medline, Embase, LILACS, SciELO, Web of Science, Scopus, CINHAL, Proquest, and PsychInfo. The search strategy used the following terms: alcohol drinking, binge drinking, alcohol-related disorders, alcoholism, alcohol addiction/use/abuse/consumption, light/moderate/social/low drinking, low birthweight, case-control studies, retrospective studies, and cohort studies. No restrictions regarding language or publication date were considered. The literature search yielded 2,383 articles, and after screening and eligibility assessment, 39 articles were included in the systematic review, and 38 studies were included in the meta-analysis. Results Maternal alcohol consumption was associated with LBW among retrospective cohort studies (relative risk [RR] = 1.37; 95%CI [confidence interval]:1.10–1.77; I2 = 98.4%; p < 0.01). Prospective cohort studies (RR = 1.11; 95%CI: 0.98–1.25; I2 = 81.5%; p < 0.01), and case-control studies (odds ration [OR] = 1.16; 95%CI: 0.68–1.97; I2 = 61.2%; p = 0.05) showed no association between alcohol and LBW. No publication bias was identified, and the meta-regression showed that the sample size influenced the high heterogeneity among retrospective cohort studies. The subgroup analysis showed differences in association between groups when compared by sample size, type of adjustment, or crude measures and publication year. Conclusions We have not found an association between alcohol consumption during gestation and LBW in the analysis in all of the subgroups. In addition, we have found a high heterogeneity between the primary studies, which is related to methodological differences in the conduction of these studies.

Outbreak of enterotoxigenic Escherichia coli O169 enteritis in schoolchildren associated with consumption of kimchi, Republic of Korea, 2012

2013 ◽  
Vol 142 (3) ◽  
pp. 616-623 ◽  
Author(s):  
S. H. CHO ◽  
J. KIM ◽  
K. -H. OH ◽  
J. K. HU ◽  
J. SEO ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cohort Studies ◽  
Case Control ◽  
Enterotoxigenic Escherichia Coli ◽  
Adjusted Relative Risk ◽  
Case Control Studies ◽  
Food Items ◽  
Laboratory Surveillance ◽  
Retrospective Cohort Studies ◽  
Foodborne Outbreaks

SUMMARYEnterotoxigenic Escherichia coli (ETEC) is now recognized as a common cause of foodborne outbreaks. This study aimed to describe the first ETEC O169 outbreak identified in Korea. In this outbreak, we identified 1642 cases from seven schools. Retrospective cohort studies were performed in two schools; and case-control studies were conducted in five schools. In two schools, radish kimchi was associated with illness; and in five other schools, radish or cabbage kimchi was found to have a higher risk among food items. Adjusted relative risk of kimchi was 5·87–7·21 in schools that underwent cohort studies; and adjusted odds ratio was 4·52–12·37 in schools that underwent case-control studies. ETEC O169 was isolated from 230 affected students, and was indistinguishable from the isolates detected from the kimchi product distributed by company X, a food company that produced and distributed kimchi to all seven schools. In this outbreak, we found that the risk of a kimchi-borne outbreak of ETEC O169 infection is present in Korea. We recommend continued monitoring regarding food safety in Korea, and strengthening surveillance regarding ETEC O169 infection through implementation of active laboratory surveillance to confirm its infection.

scholarly journals Relationship between serum uric acid, all-cause mortality and cardiovascular mortality in peritoneal dialysis patients: systematic review and meta-analysis of cohort studies

BMJ Open ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. e052274
Author(s):  
Xue Xue ◽  
Chun-Li Lu ◽  
Xin-Yan Jin ◽  
Xue-Han Liu ◽  
Min Yang ◽  
...  
Keyword(s):  
Systematic Review ◽  
Uric Acid ◽  
Cohort Studies ◽  
Retrospective Cohort ◽  
Meta Analysis ◽  
Case Control ◽  
Case Control Studies ◽  
All Cause Mortality ◽  
Retrospective Cohort Studies ◽  
The Relationship

ObjectivesTo analyse the relationship between serum uric acid (SUA), all-cause and cardiovascular (CV) mortality in peritoneal dialysis (PD) patients to inform clinical practice and future research.DesignA systematic review of observational studies.Data sourcesPubMed, Embase, Web of Science, the Cochrane Library, China National Knowledge Infrastructure (CNKI), SinoMed, Chinese Science and Technology Journal Database (VIP) and Wan Fang databases were searched from their inception to January 2021 for cohort and case–control studies reporting SUA and mortality in patients with PD.MethodsThe Newcastle-Ottawa Quality Assessment Scale was used to appraise quality of cohort and case–control studies. Effect estimates were presented as HRs with 95% CIs in a meta-analysis using STATA V.16.0. Data not suitable for pooling were synthesised qualitatively.ResultsFourteen cohort studies with 24 022 patients were included. No case–control studies were identified. For prospective cohort studies, pooled results for the highest SUA category were significantly greater than the lowest for all-cause (one study; 1278participants; HR 1.79; 95% CI 1.17 to 2.75) and CV mortality (one study; 1278 participants; HR 2.63; 1.62–4.27). An increase of 1 mg/dL in SUA level was associated with a 16% increased risk of all-cause mortality (one study; 1278 participants; HR 1.16; 1.03–1.32) and 34% increased CV mortality risk (one study; 1278 participants; HR 1.34; 1.16–1.55). For retrospective cohort studies, the highest SUA category did not demonstrate an elevated all-cause (five studies; 4570 participants; HR 1.09; 0.70–1.70) or CV mortality (three studies; 3748 participants; HR 1.00; 0.44–2.31) compared with the lowest SUA category. Additionally, there was no increase in all-cause (eight studies; 11 541 participants; HR 0.94; 0.88–1.02) or CV mortality (three studies; 7427 participants; HR 0.90; 0.76–1.06) for every 1 mg/dL increase in SUA level.ConclusionsResults of prospective and retrospective cohort studies were inconsistent. Consequently, prospective, multicentre, long-term follow-up studies are required to confirm the relationship between SUA and mortality in patients with PD.

scholarly journals Association Between Infections and Risk of Ankylosing Spondylitis: A Systematic Review and Meta-Analysis

2021 ◽  
Vol 12 ◽  
Author(s):  
Xiao Zhang ◽  
Zhe Sun ◽  
Aihong Zhou ◽  
Lei Tao ◽  
Yingxin Chen ◽  
...  
Keyword(s):  
Ankylosing Spondylitis ◽  
Cohort Studies ◽  
Subgroup Analysis ◽  
Meta Analysis ◽  
Random Effect ◽  
Epidemiological Studies ◽  
Case Control ◽  
Total Risk ◽  
Case Control Studies ◽  
Increased Risk

BackgroundPrevious literature on the association between infections and the risk of developing ankylosing spondylitis (AS) presented controversial results. This meta-analysis aimed to quantitatively investigate the effect of infections on the risk of AS.MethodsWe searched the PubMed, Embase, and Web of Science databases until March 26, 2021 for analytical epidemiological studies on the association between infections and the risk of AS. Fixed or random effect models were used to calculate total risk estimates based on study heterogeneity. Subgroup analysis, and sensitivity analysis were also performed. Publication bias was estimated using funnel plots and Begg’s test.ResultsSix case-control articles (n=1,296,239) and seven cohort articles (n=7,618,524) were incorporated into our meta-analysis. The pooled odds ratio (OR) from these case-control studies showed that infections were associated with an increased risk of AS (OR=1.46, 95% confidence interval [CI], 1.23–1.73), and the pooled relative risk (RR) from the cohort studies showed the same findings (RR=1.35, 95% CI, 1.12–1.63). Subgroup analysis showed that infections in participants with unadjusted comorbidities (OR=1.66, 95% CI, 1.35–2.03), other types of infection (OR=1.40, 95% CI, 1.15–1.70), and infection of the immune system (OR=1.46, 95% CI, 1.42–1.49) were associated with the risk of AS in case-control studies. In cohort studies, infections with adjusted comorbidities (RR=1.39, 95% CI, 1.15–1.68), viral infection (RR=1.43, 95% CI, 1.22–1.66), other types of infection (RR=1.44, 95% CI, 1.12–1.86), and other sites of infection (RR=1.36, 95% CI, 1.11–1.67) were associated with an increased risk of AS.ConclusionsThe findings of this meta-analysis confirm that infections significantly increase the risks of AS. This is helpful in providing an essential basis for the prevention of AS via the avoidance of infections.

Consumption of Artificially-sweetened Soft Drinks and Risk of Gastrointestinal Cancer: A Meta-analysis of Observational Studies

2021 ◽  
pp. 1-50
Author(s):  
Alfred Jatho ◽  
Jansen Marcos Cambia ◽  
Seung-Kwon Myung ◽  
Keyword(s):  
Cohort Studies ◽  
Observational Studies ◽  
Meta Analysis ◽  
Epidemiological Studies ◽  
Case Control ◽  
Soft Drinks ◽  
Case Control Studies ◽  
Gi Cancer ◽  
Increased Risk ◽  
Meta Analyses

Abstract Objective: There remain inconclusive findings from previous observational epidemiological studies on whether consumption of artificially-sweetened soft drinks (ASSDs) increases the risk of gastrointestinal (GI) cancer. We investigated the associations between the consumption of ASSDs and the risk of GI cancer using a meta-analysis. Design: Systematic review and meta-analysis. Setting: PubMed and EMBASE were searched using keywords until May 2020 to identify observational epidemiological studies on the association between the consumption of ASSDs and the risk of GI cancer. Subjects: Twenty-one case-control studies and 17 cohort studies with 12,397 cancer cases and 2,474,452 controls. Results: In the random-effects meta-analysis of all the studies, consumption of ASSDs was not significantly associated with the risk of overall GI cancer (odds ratio (OR)/relative risk (RR), 1.02; 95% CI, 0.92-1.14). There was no significant association between the consumption of ASSDs and the risk of overall GI cancer in the subgroup meta-analyses by study design (case-control studies: OR, 0.95; 95% CI, 0.82-1.11; cohort studies: RR, 1.14; 95% CI, 0.97-1.33). In the subgroup meta-analysis by type of cancer, consumption of ASSDs was significantly associated with the increased risk of liver cancer (OR/RR, 1.28; 95% CI,1.03-1.58). Conclusions: The current meta-analysis of observational epidemiological studies suggests that overall, there is no significant association between the consumption of ASSDs and the risk of GI cancer.

Introduction

2017 ◽  
Author(s):  
Mark Elwood
Keyword(s):  
Cohort Studies ◽  
Case Control ◽  
Randomised Trials ◽  
Case Control Studies ◽  
Causal Explanations ◽  
Bradford Hill ◽  
Definition Of ◽  
Meta Analyses ◽  
Observation Bias ◽  
Study Designs

This chapter shows the plan of the book. Later chapters will cover the definition of causation, study designs that can demonstrate causation, how results are presented, the interpretation of studies stressing the non-causal explanations of observation bias, confounding, and chance variation. Then come positive aspects of causation, the Bradford-Hill principles, systematic reviews and meta-analyses, and an overall scheme for assessing studies and diagnosing causation. Further chapters present appraisals of six published studies: randomised trials, cohort studies, and case-control studies. An appendix presents statistical methods with examples.

scholarly journals Gallifantes. Lectura crítica de estudios híbridos.

2019 ◽  
Vol 11 (7) ◽  
pp. 4
Author(s):  
Manuel Molina
Keyword(s):  
Cohort Studies ◽  
Observational Studies ◽  
Critical Appraisal ◽  
Case Control ◽  
Case Control Studies ◽  
Self Monitoring ◽  
Case Crossover

Para aquellos casos en los que los estudios observacionales clásicos no se ajustan bien a las necesidades del investigador, se han diseñado una serie de estudios híbridos que aprovechan las ventajas de los estudios convencionales y se adaptan mejor a otras situaciones. Hablaremos de los estudios de casos y controles anidados en una cohorte, de los estudios de cohorte y caso y, finalmente, de los estudios cruzados o de casos y autocontroles. ABSTRACT Chickenphants. Critical appraisal of hybrid studies For those cases in which classical observational studies do not fit well with the researcher's needs, a series of hybrid studies have been designed that take advantage of conventional studies and adapt better to other situations. We will talk about case-control studies nested in a cohort, case and cohort studies and, finally, case-crossover or self-monitoring cases studies.

scholarly journals Caffeine Intake from Coffee or Tea and Cognitive Disorders: A Meta-Analysis of Observational Studies

2015 ◽  
Vol 44 (1) ◽  
pp. 51-63 ◽  
Author(s):  
Young-Seok Kim ◽  
Sang Mi Kwak ◽  
Seung-Kwon Myung
Keyword(s):  
Cohort Studies ◽  
Meta Analysis ◽  
Cognitive Disorders ◽  
Epidemiological Studies ◽  
Case Control ◽  
Caffeine Intake ◽  
Case Control Studies ◽  
Coffee Intake ◽  
Cross Sectional ◽  
Cross Sectional Studies

Background: Observational epidemiological studies such as cross-sectional, case-control, and cohort studies have reported inconsistent findings regarding the association between caffeine intake from coffee or tea and the risk of cognitive disorders such as dementia, Alzheimer's disease, cognitive impairment, and cognitive decline. Methods: We searched PubMed and EMBASE in September 2014. Three evaluators independently extracted and reviewed articles, based on predetermined selection criteria. Results: Out of 293 articles identified through the search and bibliographies of relevant articles, 20 epidemiological studies from 19 articles, which involved 31,479 participants (8,398 in six cross-sectional studies, 4,601 in five case-control studies, and 19,918 in nine cohort studies), were included in the final analysis. The pooled odds ratio (OR) or relative risk (RR) of caffeine intake from coffee or tea for cognitive disorders (dementia, Alzheimer's disease, cognitive impairment, and cognitive decline) was 0.82 (95% confidence interval [CI], 0.67-1.01, I2 = 63.2%) in a random-effects meta-analysis. In the subgroup meta-analysis by caffeine sources, the summary OR or RR of coffee intake was 0.83 (95% CI, 0.70-0.98; I2 = 44.8%). However, in the subgroup meta-analysis by study design, the summary estimates (RR or OR) of coffee intake for cognitive disorders were 0.70 (95% CI, 0.50-0.98; I2 = 42.0%) for cross-sectional studies, 0.82 (95% CI, 0.55-1.24; I2 = 33.4%) for case-control studies, and 0.90 (95% CI, 0.59-1.36; I2 = 60.0%) for cohort studies. Conclusions: This meta-analysis found that caffeine intake from coffee or tea was not associated with the risk of cognitive disorders.

Ethnic differences in risk factors for subarachnoid hemorrhage

2007 ◽  
Vol 107 (3) ◽  
pp. 522-529 ◽  
Author(s):  
Vibhor Krishna ◽  
Dong H. Kim
Keyword(s):  
Risk Factors ◽  
Subarachnoid Hemorrhage ◽  
Alcohol Consumption ◽  
Cohort Studies ◽  
Odds Ratio ◽  
Case Control ◽  
Ethnic Composition ◽  
Effect Estimate ◽  
Case Control Studies ◽  
Current Smoking

Object Studies on risk factors for subarachnoid hemorrhage (SAH) show heterogeneity. For example, hypertension has been found to be a significant risk factor in some studies but not in others. The authors hypothesized that differences in the ethnicity of the populations studied could account for these findings. Methods A metaanalysis was performed using 17 case-control and 10 cohort studies that met specified inclusion criteria. The authors used a random-effect model to calculate the pooled effect estimates for current smoking, hypertension, and alcohol consumption. A meta–regression analysis was performed using the ethnic composition of the study populations as a covariate. Studies were classified as multiethnic or monoethnic, and the pooled effect estimates were compared. Results Analysis of the cohort studies yielded a pooled effect estimate or risk ratio of 3.18 (95% confidence interval [CI] 2.37–4.26) for current smoking, 3.05 (95% CI 2.09–4.44) for hypertension, and 2.46 (95% CI 1.42–4.24) for alcohol consumption at a rate of 150 g/week or more. The results were similar for the case-control studies. For current smoking, the ethnic composition of the study population was a statistically significant predictor of heterogeneity among case-control studies (p < 0.001, even after application of the Bonferroni correction). The risk for SAH among current smokers was higher in multiethnic populations (odds ratio 3.832) than in monoethnic populations (odds ratio 2.487). Conclusions The results of this metaanalysis suggest that differences in susceptibility to the harmful health effects of smoking may be one cause of the observed differences in SAH incidence for different ethnic groups. The role of ethnicity in risk factors for SAH should be considered in future studies.

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