Epidemiology Overview and Analytical Methods

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Questions and Answers

What is the primary purpose of experimental epidemiology?

  • To investigate causal relationships between exposures and outcomes (correct)
  • To assess individuals based on their outcome history
  • To compare outcomes between different diseases
  • To measure the prevalence of exposure in a population

Which type of study is considered the gold standard in experimental studies?

  • Randomized controlled trials (RCTs) (correct)
  • Cross-sectional studies
  • Quasi-experimental studies
  • Case-control studies

What is a main characteristic of quasi-experimental studies?

  • They do not have a control group. (correct)
  • They always use randomization.
  • They focus solely on case-control comparisons.
  • They measure exposure at multiple time points.

How do case-control studies assess exposure?

<p>By measuring exposure history retrospectively (B)</p>
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Which type of bias results from systematic errors in choosing participants?

<p>Selection bias (C)</p>
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What can bias in epidemiological studies lead to?

<p>False conclusions or misleading recommendations (D)</p>
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In which scenario are quasi-experimental studies most commonly employed?

<p>When interventions are naturally occurring (C)</p>
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What do cross-sectional studies primarily measure?

<p>The prevalence of exposure and outcome at a single point in time (B)</p>
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What is the primary focus of analytical epidemiology?

<p>Measuring associations between exposures and outcomes (A)</p>
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Which type of epidemiological study follows a group of individuals over time to compare outcomes based on exposure?

<p>Cohort study (C)</p>
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What is a limitation common to both analytical and experimental epidemiological studies?

<p>They can be affected by bias and confounding (A)</p>
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What distinguishes experimental epidemiology from analytical epidemiology?

<p>Experimental epidemiology manipulates exposure in a controlled environment (A)</p>
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Which of the following is NOT a common type of analytical study?

<p>Longitudinal study (A)</p>
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What type of study is used to investigate causal relationships hinted at by observational studies?

<p>Experimental epidemiology (B)</p>
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What is the primary issue caused by selection bias in research?

<p>It makes the sample differ from the overall population. (C)</p>
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Which option describes a common characteristic of cohort studies?

<p>They compare outcomes between exposed and unexposed groups (A)</p>
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Which of the following is an example of self-selection bias?

<p>A group of college students chooses to participate in a health study. (D)</p>
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What method is primarily used in descriptive epidemiology?

<p>Describing patterns of disease occurrence (D)</p>
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What method can be used to minimize selection bias?

<p>Using randomization to assign treatments to participants. (A)</p>
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Which bias occurs when people remember things differently due to their condition?

<p>Recall bias (A)</p>
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What is one method to minimize information bias in research studies?

<p>Standardizing data collection methods. (B)</p>
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What is the role of appropriate control groups in minimizing bias?

<p>They provide a comparison for assessing the treatment's effect. (C)</p>
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What problem does measurement bias refer to?

<p>Using inaccurate tools for assessing outcomes. (D)</p>
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Which component is important for effectively minimizing observer bias?

<p>Providing training and calibration for data collectors. (A)</p>
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What is confounding bias primarily associated with?

<p>Both exposure and outcome that are not intermediate steps in the causal pathway (B)</p>
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Which of the following best describes 'age confounding'?

<p>Age is related to both exposure and outcome but not a consequence of the exposure (A)</p>
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Which method is NOT a strategy to minimize confounding bias in study design?

<p>Observation without adjustment (A)</p>
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What is a consequence of publication bias?

<p>Distortion of the literature regarding true effect size (A)</p>
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How does randomization help prevent confounding bias?

<p>By evenly distributing known and unknown confounders across study groups (C)</p>
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Which of the following reflects a common ethical issue related to publication bias?

<p>Suppressing negative results for financial gain (C)</p>
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What is socioeconomic status (SES) confounding related to?

<p>It relates to both exposure and outcome, not as a consequence of either (D)</p>
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Which technique is NOT typically used to adjust for confounders during data analysis?

<p>Random sampling (C)</p>
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What is a comprehensive literature search aimed at addressing?

<p>Identifying unpublished or hidden studies. (C)</p>
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Which method can help to prevent selective reporting in research?

<p>Registering study protocols before the study begins. (C)</p>
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What characterizes recall bias in case-control studies?

<p>Cases may recall their exposure to risk factors better than controls. (D)</p>
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How can standardized questionnaires minimize recall bias?

<p>By using consistent formats and memory aids. (D)</p>
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What does the use of objective measurements entail?

<p>Employing biological or physical markers for measuring exposures. (D)</p>
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Why is timely data collection important in research?

<p>It reduces the likelihood of recall bias. (A)</p>
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What is the main focus of analytical and experimental epidemiology?

<p>Quantifying associations between exposures and outcomes. (D)</p>
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How does contacting authors for unpublished data help in research?

<p>It lessens the bias introduced by published studies alone. (A)</p>
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Flashcards

Analytical Epidemiology

Measures relationship between an exposure and disease, using individual data, not population data.

Experimental Epidemiology

Uses controlled experiments to confirm causal links, following observational studies.

Cohort Studies

Follow groups over time, comparing outcomes with and without exposure.

Case-Control Studies

Compare people with a disease to those without, looking for past exposures.

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Cross-Sectional Studies

Collect data on exposure and disease at a single point in time.

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Descriptive Epidemiology

Describes patterns of disease by time, place, person.

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Incidence

Number of new cases of a disease within a specific time period.

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Relative Risk

Ratio of disease risk among exposed to disease risk among unexposed.

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Odds Ratio

A measure of association between exposure and disease in a case-control study, showing how much more likely cases are to have been exposed than controls.

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Prevalence Ratio

Measures the association between exposure and disease in a cross-sectional study, showing how much more likely exposed individuals are to have the disease.

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Randomized Controlled Trial (RCT)

The gold standard of experimental studies, where participants are randomly assigned to receive an intervention or a placebo to test the effectiveness of the intervention.

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Quasi-Experimental Study

Similar to RCTs but without random assignment or a control group, used when RCTs are not feasible or ethical.

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Bias

Systematic error in a study that can affect the validity of results, making it difficult to determine the true relationship between exposure and outcome.

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Confounding Bias

A bias that occurs when a factor is associated with both the exposure and the outcome, and it is not a consequence of the exposure. This can overestimate or underestimate the true association between exposure and outcome.

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Age Confounding

When age influences both exposure and outcome, but is not a direct consequence of the exposure.

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Socioeconomic Status Confounding

When socioeconomic status (SES) is linked to both exposure and outcome, and is not caused by the exposure.

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Minimize Confounding Bias

Strategies to control for confounding factors during study design and data analysis.

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Matching

A study design technique where participants are grouped based on specific characteristics to minimize confounding.

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Stratification

Dividing participants into groups based on confounder levels for analysis.

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Publication Bias

Studies with positive or significant results are more likely to be published than those with negative or null results, creating a skewed representation of the evidence.

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Consequences of Publication Bias

Publication bias can lead to overestimation or underestimation of the true effect, wasted resources, and ethical concerns.

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Selection Bias

A problem where researchers choose participants in a non-random way, making the sample different from the whole population.

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Self-Selection Bias

This bias happens when participants choose to join or leave a study based on their own preferences, which may be related to the study's topic.

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Randomization

Choosing participants by chance to make sure groups receiving different treatments are similar in other ways. Helps avoid unfair comparisons in studies.

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Control Group

A group that doesn't receive the new treatment, but is similar to the group that does. Helps avoid false associations in studies.

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Representative Sampling

Choosing participants who match the features and diversity of the whole population the study wants to apply to.

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Recall Bias

When people remember things differently based on whether they have a certain condition or belong to a certain group.

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Observer Bias

When researchers see or record things differently based on whether the participants have a certain condition or belong to a certain group.

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Measurement Bias

When tools or methods used to assess the study topic are inaccurate, unreliable, or inconsistent across groups.

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Comprehensive Literature Search

A thorough search across multiple databases and sources to identify all relevant studies, regardless of publication status, to avoid missing important findings.

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Inclusion of Unpublished Studies

Actively seeking out unpublished research, such as contacting researchers, to include these studies in analysis, ensuring a more complete picture.

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Study Protocol Registration

Registering the design, methods, and outcome measures of a study before it begins, making it publicly accessible, thereby increasing transparency and reducing selective reporting.

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Standardized Questionnaires

Structured surveys with clear, specific questions and multiple-choice answers to minimize recall bias and ensure consistent data collection.

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Objective Measurements

Using biological, physical, or chemical markers to measure exposure or outcomes, reducing reliance on subjective recall.

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Timely Data Collection

Collecting data as close as possible to the event's occurrence to minimize recall bias and ensure accuracy.

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Study Notes

Analytical & Experimental Epidemiology

  • Epidemiology is the study of the distribution and determinants of health and disease in populations.
  • Epidemiological studies are categorized as descriptive and analytical.
  • Descriptive epidemiology describes disease patterns by time, place, and person.
  • Analytical epidemiology measures associations between exposures and outcomes and studies causal relationships.
  • Experimental epidemiology is a subset of analytical epidemiology, manipulating exposure or intervention in controlled settings.

Analytical Epidemiology

  • Analytical epidemiology uses observational studies comparing groups with varying exposure levels.
  • Its goal is to identify associations between exposures and outcomes and to evaluate causal relationships.
  • Common types of analytical studies include cohort studies, case-control studies, and cross-sectional studies.

Cohort Studies

  • Cohort studies follow a group of individuals over time, comparing outcomes with unexposed individuals.
  • They can assess incidence and relative risk of disease, potentially prospectively or retrospectively.

Case-Control Studies

  • Case-control studies compare individuals with a disease to those without, assessing exposure history.
  • They are primarily retrospective and measure the odds ratio of exposure.

Cross-Sectional Studies

  • Cross-sectional studies measure the prevalence of exposure and outcome in a population at a single point in time.
  • They are also known as prevalence studies and assess the prevalence ratio of exposure.

Experimental Epidemiology

  • Experimental epidemiology manipulates exposure or intervention in a controlled setting.
  • The goal is to investigate causal relationships and assess intervention effectiveness/safety.
  • A common example is a randomized controlled trial (RCT).
  • Quasi-experimental studies are similar to RCTs but do not use randomization or control groups.

Bias in Epidemiological Studies

  • Bias is a systematic error leading to inaccurate estimates of exposure-outcome associations.
  • Bias can stem from various sources such as selecting participants, measuring exposure/outcome, data analysis, or result interpretation.
  • Bias can affect study validity and reliability, potentially leading to false conclusions.

Selection Bias

  • Selection bias occurs when researchers' choice of participants isn't random, leading to a sample differing from the whole population.
  • Self-selection bias occurs when participants choose to join or leave a study based on personal preferences or characteristics.

Methods to Minimize Selection Bias

  • Randomization ensures group similarity in exposure.
  • Using appropriate control groups matched to cases enhances comparability.
  • Representative sampling ensures the sample mirrors the population.

Information Bias

  • Information bias arises from inaccuracies in data collection related to participant condition or researcher perception.
  • Recall bias occurs when participants remember events inconsistently based on their condition.
  • Observer bias occurs when researchers record data differently based on participant conditions or traits.
  • Measurement bias results from inaccurate or inconsistent measurement tools across groups.

Methods to Minimize Information Bias

  • Standardized methods of data collection ensure consistent techniques among participants.
  • Data collectors' training and calibration ensure uniformity in data gathering.
  • Validated measurement tools help ensure data quality.

Confounding Bias

  • Confounding bias occurs when a factor, correlated with both the exposure and the outcome, influences the observed association.
  • Age and socioeconomic status are examples of confounders.

Methods to Minimize Confounding Bias

  • Study design incorporating strategies such as matching or stratification.
  • Statistical techniques to adjust for confounder effects.
  • Randomization in experimental studies helps prevent confounding.

Publication Bias

  • Publication bias favours studies with significant results being published, while studies with negative results remain unpublished.
  • Publication bias creates skew in literature representation, and it affects literature distortion, potentially leading to over/underestimations of the true effects.

Methods to Address Publication Bias

  • Comprehensive literature searches, regardless of publication status, help identify unpublished data.
  • Inclusion of unpublished data enhances representation of the full evidence.
  • Registering study protocols promotes transparency and reduces selective reporting.

Recall Bias in Cohort Studies

  • In cohort studies, recall bias occurs when participants have difficulty or inconsistently remember exposures related to the outcome that appears after a long time.

Recall Bias in Case-Control Studies

  • In case-control studies, participants may recall prior exposures to risk factors differently.

Methods to Minimize Recall Bias

  • Standardized questionnaires with clear questions and memory aids can minimize inconsistency.
  • Objective measurements using biological or chemical markers help reduce variability.
  • Collecting data as close as possible to events decreases memory inaccuracies.

Conclusion

  • Analytical and experimental methodologies identify and quantify population exposure-outcome associations.
  • Minimizing bias is critical for reliable and valid epidemiological conclusions.
  • Numerous methods exist to mitigate bias at various stages.

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