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Neurological Sciences : Official... Oct 2022To combine the current scientific literature evidence and elucidate the differences of lead (Pb) bioaccumulation in human tissues by comparing amyotrophic lateral... (Meta-Analysis)
Meta-Analysis Review
AIM
To combine the current scientific literature evidence and elucidate the differences of lead (Pb) bioaccumulation in human tissues by comparing amyotrophic lateral sclerosis (ALS) patients and healthy controls.
METHODS
We systematically searched for case-control studies on the association of Pb levels with ALS, in human cells, tissues, and body fluids (nervous tissue, muscle, blood, cerebrospinal fluid, urine, skin appendages). Then, we performed a meta-analysis for all the tissues in which at least five case-control studies were available: whole blood (9 studies), serum/plasma (5 studies), and cerebrospinal fluid (CSF) (6 studies). Differences between cases and controls were evaluated using standardized mean difference, and combined estimates were derived using random effect maximum likelihood (REML) meta-analyses.
RESULTS
Among 1734 records, we identified 46 full-text studies, of which 14 case-control studies met the meta-analysis inclusion criteria. We found higher Pb levels in ALS cases than controls in blood (standardized mean difference (SMD) = 0.61; 95% confidence interval (CI) 0.20, 1.01; p = 0.003), plasma/serum (SMD = 0.27; 95% CI - 0.16, 0.70; p = 0.26), and CSF (SMD = 0.53; 95% CI - 0.09, 1.15; p = 0.09).
CONCLUSIONS
This work provides further evidence of the association between Pb bioaccumulation and ALS in body fluids. The lack of association studies in solid tissues did not allow a robust meta-analysis. Future prospective studies are needed to clarify the causality in the association of Pb bioaccumulation with ALS.
Topics: Amyotrophic Lateral Sclerosis; Biomarkers; Case-Control Studies; Humans; Lead
PubMed: 35809130
DOI: 10.1007/s10072-022-06237-y -
Foodborne Pathogens and Disease Apr 2012Epidemiologists have used case-control studies to investigate enteric disease outbreaks for many decades. Increasingly, case-control studies are also used to investigate... (Review)
Review
Epidemiologists have used case-control studies to investigate enteric disease outbreaks for many decades. Increasingly, case-control studies are also used to investigate risk factors for sporadic (not outbreak-associated) disease. While the same basic approach is used, there are important differences between outbreak and sporadic disease settings that need to be considered in the design and implementation of the case-control study for sporadic disease. Through the International Collaboration on Enteric Disease "Burden of Illness" Studies (the International Collaboration), we reviewed 79 case-control studies of sporadic enteric infections caused by nine pathogens that were conducted in 22 countries and published from 1990 through to 2009. We highlight important methodological and study design issues (including case definition, control selection, and exposure assessment) and discuss how approaches to the study of sporadic enteric disease have changed over the last 20 years (e.g., making use of more sensitive case definitions, databases of controls, and computer-assisted interviewing). As our understanding of sporadic enteric infections grows, methods and topics for case-control studies are expected to continue to evolve; for example, advances in understanding of the role of immunity can be used to improve control selection, the apparent protective effects of certain foods can be further explored, and case-control studies can be used to provide population-based measures of the burden of disease.
Topics: Case-Control Studies; Disease Outbreaks; Global Health; Humans; Intestinal Diseases; Research Design; Risk Factors
PubMed: 22443481
DOI: 10.1089/fpd.2011.1065 -
American Journal of Epidemiology Oct 2022In multiply matched case-control studies, a number of cases and controls may be included in each matched set. However, when per-participant costs between cases and...
In multiply matched case-control studies, a number of cases and controls may be included in each matched set. However, when per-participant costs between cases and controls differ, investigators should be aware of how the numbers of cases and controls per matched set affect the overall total study cost. Traditional statistical approaches to designing case-control studies do not account for study costs. Given an effect size, the power to detect differences is typically a function of the numbers of cases and controls within each matched set. Therefore, the same level of statistical power will be achieved based on various combinations of the numbers of cases and controls. Typical matched case-control studies match a case to a number of controls by levels of 1 or more known factors. Several authors have shown that for study designs with 1 case per matched set, the optimal number of controls within each matched set that minimizes the total study cost is the square root of the ratio of the cost of a case to the cost of a control. Herein, we extend this result to the setting of a multiply matched case-control study design, when 1 or more cases are matched to controls within each matched set. A Shiny web application implementation of the proposed methods is presented.
Topics: Humans; Case-Control Studies; Research Design
PubMed: 35916344
DOI: 10.1093/aje/kwac138 -
European Journal of Epidemiology Jan 2018Misconceptions about the impact of case-control matching remain common. We discuss several subtle problems associated with matched case-control studies that do not arise...
Misconceptions about the impact of case-control matching remain common. We discuss several subtle problems associated with matched case-control studies that do not arise or are minor in matched cohort studies: (1) matching, even for non-confounders, can create selection bias; (2) matching distorts dose-response relations between matching variables and the outcome; (3) unbiased estimation requires accounting for the actual matching protocol as well as for any residual confounding effects; (4) for efficiency, identically matched groups should be collapsed; (5) matching may harm precision and power; (6) matched analyses may suffer from sparse-data bias, even when using basic sparse-data methods. These problems support advice to limit case-control matching to a few strong well-measured confounders, which would devolve to no matching if no such confounders are measured. On the positive side, odds ratio modification by matched variables can be assessed in matched case-control studies without further data, and when one knows either the distribution of the matching factors or their relation to the outcome in the source population, one can estimate and study patterns in absolute rates. Throughout, we emphasize distinctions from the more intuitive impacts of cohort matching.
Topics: Bias; Case-Control Studies; Cohort Studies; Confounding Factors, Epidemiologic; Humans; Matched-Pair Analysis; Odds Ratio; Research Design
PubMed: 29101596
DOI: 10.1007/s10654-017-0325-0 -
Annals of Epidemiology Jun 2021Meta-analyses of observational studies reduce the role of chance but also introduce bias because the individual component studies are not randomized. Further, it is... (Meta-Analysis)
Meta-Analysis
PURPOSE
Meta-analyses of observational studies reduce the role of chance but also introduce bias because the individual component studies are not randomized. Further, it is plausible that the bias may be different in case-control and cohort studies. We explored these issues in meta-analyses of observational studies of Opioid Use Disorder (OUD).
METHODS
From a systematic literature review of 152 published meta-analyses, 11 fulfilled the initial inclusion criteria of observational studies of OUD. Of these, 9 were meta-analyses of case-control studies and 2 were meta-analyses of cohort studies but only 4 (3 case-control and 1 cohort) targeted more than one specific chromosomal location.
RESULTS
The meta-analyses of the 3 case-control studies, which included 13 individual studies, identified 12 different single nucleotide polymorphisms on 6 different genes on 5 different chromosomes. None was the same as the gene on Chromosome 15 identified from the meta-analysis of the cohort studies.
CONCLUSIONS
These data, from genetic studies, suggest biases are different in meta-analyses of case-control and cohort studies, perhaps due to greater selection bias in case-control studies. These observations have potential importance in the application of meta-analyses to many common and serious diseases, as well as genomics and precision medicine, including OUD.
Topics: Bias; Case-Control Studies; Cohort Studies; Genomics; Humans; Precision Medicine
PubMed: 33640484
DOI: 10.1016/j.annepidem.2021.02.013 -
Annals of Work Exposures and Health Nov 2018Retrospective occupational exposure assessment has been challenging in case-control studies in the general population. We aimed to review (i) trends of different... (Review)
Review
INTRODUCTION
Retrospective occupational exposure assessment has been challenging in case-control studies in the general population. We aimed to review (i) trends of different assessment methods used in the last 40 years and (ii) evidence of reliability for various assessment methods.
METHODS
Two separate literature reviews were conducted. We first reviewed all general population cancer case-control studies published from 1975 to 2016 to summarize the exposure assessment approach used. For the second review, we systematically reviewed evidence of reliability for all methods observed in the first review.
RESULTS
Among the 299 studies included in the first review, the most frequently used assessment methods were self-report/assessment (n = 143 studies), case-by-case expert assessment (n = 139), and job-exposure matrices (JEMs; n = 82). Usage trends for these methods remained relatively stable throughout the last four decades. Other approaches, such as the application of algorithms linking questionnaire responses to expert-assigned exposure estimates and modelling of exposure with historical measurement data, appeared in 21 studies that were published after 2000. The second review retrieved 34 comparison studies examining methodological reliability. Overall, we observed slightly higher median kappa agreement between exposure estimates from different expert assessors (~0.6) than between expert estimates and exposure estimates from self-reports (~0.5) or JEMs (~0.4). However, reported reliability measures were highly variable for different methods and agents. Limited evidence also indicates newer methods, such as assessment using algorithms and measurement-calibrated quantitative JEMs, may be as reliable as traditional methods.
CONCLUSION
The majority of current research assesses exposures in the population with similar methods as studies did decades ago. Though there is evidence for the development of newer approaches, more concerted effort is needed to better adopt exposure assessment methods with more transparency, reliability, and efficiency.
Topics: Algorithms; Case-Control Studies; Environmental Monitoring; Humans; Occupational Exposure; Occupational Health; Reproducibility of Results; Retrospective Studies; Self Report
PubMed: 30239580
DOI: 10.1093/annweh/wxy080 -
Chemosphere Mar 2022Environmental chromium exposure may cause impaired development of children. We conducted a systematic review and meta-analysis. Electronic databases including PubMed,... (Meta-Analysis)
Meta-Analysis Review
Environmental chromium exposure may cause impaired development of children. We conducted a systematic review and meta-analysis. Electronic databases including PubMed, Embase, Web of Science and CINAHL were searched to identify case-control studies that reported childhood Cr exposure and cognitive development. The Newcastle-Ottawa Scale (NOS) was used to ensure the quality of the included studies. Cr levels were compared in cases and controls, and a random effect meta-analysis was performed using Stata version 16. Twelve of 61 studies identified in the literature search were eligible for this analysis. Hair, serum and urine Cr measurements were reported by seven, two and one studies, respectively. In addition, one study reported both serum and hair Cr exposure and another reported urine and hair Cr exposure. The pooled standard mean differences (SMD) showed that hair Cr levels were non-significantly lower among children with cognitive defects (-0.01 μg/g, 95% CI: -0.04, 00, p = 0.27). In serum and urine, the pooled SMD was higher in children with cognitive deficits compared with healthy control children (0.32 μg/g, 95% CI: -0.78, 1.42, p = 0.56 and 0.64 μg/g, CI: -0.07,1.36, p = 0.08; respectively). In summary, this systematic review found no significant differences in hair, serum and urine Cr levels between children with cognitive deficits and healthy control children when all study data were pooled in the meta-analysis. Larger studies using standardized criteria and longitudinal assessment of cognitive development are needed to determine whether there is a dose response effect of childhood Cr exposure on cognitive development of children.
Topics: Case-Control Studies; Child; Chromium; Cognition; Hair; Humans
PubMed: 34813844
DOI: 10.1016/j.chemosphere.2021.133017 -
Statistical Methods in Medical Research Mar 2019Sample size calculations are needed to design and assess the feasibility of case-control studies. Although such calculations are readily available for simple...
Sample size calculations are needed to design and assess the feasibility of case-control studies. Although such calculations are readily available for simple case-control designs and univariate analyses, there is limited theory and software for multivariate unconditional logistic analysis of case-control data. Here we outline the theory needed to detect scalar exposure effects or scalar interactions while controlling for other covariates in logistic regression. Both analytical and simulation methods are presented, together with links to the corresponding software.
Topics: Aged; Algorithms; Biomedical Research; Breast Neoplasms; Case-Control Studies; Female; Humans; Logistic Models; Middle Aged; Research Design; Sample Size
PubMed: 29145780
DOI: 10.1177/0962280217737157 -
Annals of Clinical and Translational... Mar 2021
Topics: Bayes Theorem; Brain Diseases; COVID-19; Case-Control Studies; Humans; Morbidity; SARS-CoV-2
PubMed: 33512092
DOI: 10.1002/acn3.51288 -
Injury Prevention : Journal of the... Dec 2020Conducting case-control studies using the National Violent Death Reporting System (NVDRS) has the potential to introduce selection bias and misclassification through...
Conducting case-control studies using the National Violent Death Reporting System (NVDRS) has the potential to introduce selection bias and misclassification through control selection. Some studies that use NVDRS compare groups of individuals who died by one mechanism, intent or circumstance, to individuals who died by another mechanism, intent or circumstance. For aetiological studies within NVDRS, the use of controls who had a different type of violent death has the potential to introduce selection bias, while relying on narrative summaries for exposure measurement may result in misclassification. We discuss these two methodological issues, and identify an unusual circumstance in which selection of live controls within NVDRS can be employed.
Topics: Case-Control Studies; Cause of Death; Homicide; Humans; Population Surveillance; Selection Bias; Suicide; Violence
PubMed: 32792366
DOI: 10.1136/injuryprev-2020-043865