Epidemiology: Bias and Confounding
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Questions and Answers

Which type of bias involves skewed results due to a population being under observation?

  • Recall bias
  • Reporting bias
  • Wish bias
  • Surveillance bias (correct)

    • What should be considered when evaluating epidemiological associations?

  • Whether the association could be due to chance.
  • Whether the association could be due to bias.
  • Whether confounding variables account for the relationship.
  • All of the above. (correct)

    • What is the primary consequence of bias in epidemiological research?

  • It obscures the true relationship between exposure and outcome. (correct)
  • It ensures generalizability of findings to all populations.
  • It leads to random variations in study results.
  • It guarantees statistical significance.

    • Which of the following best describes a 'systematic error' in the context of epidemiological studies?

    <p>A consistent error that skews results in a particular direction. (B)</p> Signup and view all the answers

    In research, what could occur if the relative risk (RR) is underestimated?

    <p>Increased confidence in the findings (B)</p> Signup and view all the answers

    What is the primary concern when assessing whether sigmoidoscopy screening changes mortality rates from colorectal cancer in a case control study, according to Selby JV et al. (1992)?

    <p>Different characteristics between screened and unscreened individuals (C)</p> Signup and view all the answers

    In which stage(s) of a study can bias be introduced?

    <p>During the design, conduct, or analysis of the study. (A)</p> Signup and view all the answers

    Using the distribution of pancreatic cancer cases and controls by coffee-drinking habits, what can be inferred from the adjusted relative risk for males (2.6 with a 95% confidence interval of 1.2-5.4)?

    <p>Coffee drinking might increases the risk of pancreatic cancer in males. (D)</p> Signup and view all the answers

    What distinguishes selection bias from other forms of bias in epidemiological studies?

    <p>It arises from the way participants are chosen for the study. (D)</p> Signup and view all the answers

    Why is it often impossible to completely eliminate research bias?

    <p>Perfect control over all variables is unachievable. (A)</p> Signup and view all the answers

    Which type of bias is most likely to occur when participants in a study alter their responses because of the circumstances of their diagnosis?

    <p>Reporting bias (C)</p> Signup and view all the answers

    In the associations provided, how is smoking related to low birth weight?

    <p>Causal (B)</p> Signup and view all the answers

    What is the primary strategy for dealing with bias in epidemiological research?

    <p>Attempting to avoid it during the design phase and minimizing its effect during analysis. (B)</p> Signup and view all the answers

    In the context of epidemiology, what does confounding refer to?

    <p>A distortion of the association between an exposure and an outcome due to a third variable (B)</p> Signup and view all the answers

    Which scenario exemplifies selection bias?

    <p>A study only includes volunteers who are highly motivated and health-conscious. (D)</p> Signup and view all the answers

    What is the potential outcome of selection bias in a study?

    <p>An apparent association is observed, when in reality exposure and disease are unrelated. (A)</p> Signup and view all the answers

    In a case-control study examining the link between a specific environmental exposure and a rare disease, what is the most likely manifestation of selection bias?

    <p>Cases are more likely to be selected if they have the exposure, or controls are more likely to be selected if they are unexposed. (A)</p> Signup and view all the answers

    What is the primary concern regarding non-response bias in an epidemiological study?

    <p>The characteristics of respondents differ systematically from those of non-respondents, leading to biased results. (C)</p> Signup and view all the answers

    In a study investigating the association between smoking and respiratory illness, a significantly lower response rate is observed among smokers in a mailed questionnaire survey. What type of bias is most concerning in this scenario?

    <p>Non-response bias, because the lower response rate among smokers may lead to a skewed representation of the true association. (A)</p> Signup and view all the answers

    What characterizes information bias in epidemiological research?

    <p>Systematic errors in the way data about exposures and/or outcomes are collected, leading to inaccurate information. (B)</p> Signup and view all the answers

    What is the most effective mitigation strategy for interviewer bias?

    <p>Blinding interviewers to the outcome status of participants. (C)</p> Signup and view all the answers

    In a case-control study, some individuals with the disease are mistakenly classified as not having the disease (controls), and vice versa. What type of bias does this exemplify?

    <p>Misclassification bias. (A)</p> Signup and view all the answers

    In differential misclassification, how does the misclassification rate vary between study groups?

    <p>The misclassification rate differs between study groups. (C)</p> Signup and view all the answers

    What is the typical effect of non-differential misclassification on the risk ratio (RR)?

    <p>It biases the RR towards the null value (RR = 1). (D)</p> Signup and view all the answers

    What is the relationship between smoking and coffee drinking, as described?

    <p>Smoking is associated with coffee drinking, but is not a result of coffee drinking. (B)</p> Signup and view all the answers

    In the context of the provided information on pancreatic cancer, what is a confounding variable?

    <p>A variable that interferes with the observed association, is associated with the putative causal factor, and is causally associated with the outcome. (C)</p> Signup and view all the answers

    Which of the following is NOT a method to control for confounders in the design of a study?

    <p>Multivariate analysis (B)</p> Signup and view all the answers

    According to the data presented, what can be inferred regarding coffee consumption and the adjusted relative risk for pancreatic cancer in males?

    <p>The adjusted relative risk is generally stable for those who consume 1-2 cups/day or more of coffee compared to those who consume none. (A)</p> Signup and view all the answers

    Based on the data, what is the estimated relative risk of pancreatic cancer for current smokers who drink 3 or more cups of coffee per day, compared to the reference group?

    <p>4.6 (D)</p> Signup and view all the answers

    According to the estimates provided, what is the relative risk of pancreatic cancer for ex-smokers who drink $1-2$ cups of coffee per day?

    <p>4.0 (B)</p> Signup and view all the answers

    What is the reference category used when estimating the relative risk associated with coffee and cigarette use?

    <p>Individuals who use neither cigarettes nor coffee. (C)</p> Signup and view all the answers

    In the study referenced, which variable was adjusted for when estimating the relative risk of pancreatic cancer associated with coffee and cigarette use?

    <p>Sex and age (D)</p> Signup and view all the answers

    Which of the following statements accurately describes the effect of stratification in controlling for confounders?

    <p>Stratification involves dividing the study population into subgroups based on the confounder. (A)</p> Signup and view all the answers

    What is the relationship between coffee consumption and pancreatic cancer when not considering other factors?

    <p>The observed association between coffee consumption and pancreatic cancer may be the result of confounding by smoking. (C)</p> Signup and view all the answers

    Flashcards

    Epidemiology

    The study of how diseases affect the health and illness of populations.

    Bias

    Any systematic error in a study that leads to an incorrect estimate of an exposure-outcome association.

    Random Errors

    Errors caused by chance and lead to variability in study results.

    Systematic Errors

    Errors that occur in a predictable pattern affecting the study's validity.

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    Selection Bias

    When the selection of cases and controls results in an apparent association that does not exist.

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    Confounding

    A situation where an outside factor influences both the exposure and the outcome, leading to a false association.

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    Minimizing Bias

    Efforts made during study design and analysis to reduce systematic errors.

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    Research Errors

    Inaccuracies in data collection or analysis that can lead to false conclusions.

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    Information Bias

    A distortion in data collection methods affecting study outcomes.

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    Surveillance Bias

    Bias occurring when a monitored population is subjected to different scrutiny.

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    Recall Bias

    Errors in recollection by participants affecting study accuracy.

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    Reporting Bias

    A systematic difference in the way data is reported or perceived.

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    Relative Risk (RR) Underestimation

    When the true risk is lower than reported, leading to overconfidence in findings.

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    Causal Association

    A relationship where one factor directly influences another.

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    Spurious Association

    A false relationship likely caused by confounding variables.

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    Confounding Variables

    Factors that confuse the association between exposure and outcome.

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    Case-Control Study

    A study where cases are more likely to be selected if exposed, and controls if unexposed.

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    Non-Response Bias

    Occurs when the response rate differs among subjects, distorting associations.

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    Interviewer Bias

    Bias introduced when interviewers influence responses based on knowledge of outcomes.

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    Misclassification Bias

    Occurs when subjects are wrongly classified into exposure or outcome groups.

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    Differential vs Non-Differential Misclassification

    Differential: misclassification differs between groups; Non-differential: misclassification occurs equally.

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    Pancreatic Cancer Risk Factors

    Smoking is a known risk factor for pancreatic cancer.

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    Causal Factor (A)

    The putative factor believed to cause the outcome in a study.

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    Outcome (B)

    The health effect or result being studied in association with exposure.

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    Controlling for Confounders

    Methods used to account for confounding variables in research.

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    Randomization

    Assigning participants randomly to treatment or control groups to minimize bias.

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    Restriction

    Excluding participants with a confounding variable from a study.

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    Stratification

    Dividing subjects into subgroups to control for confounding.

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    Adjusted Relative Risk

    A measure of risk while controlling for confounders in a study.

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    Coffee Drinking and Cancer

    Coffee consumption is associated with pancreatic cancer risk, confounded by smoking.

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    Study Notes

    Epidemiology: Bias and Confounding

    • Research errors include random errors (sampling, lack of precision, variability in measurement) and systematic errors (bias).
    • Bias is any systematic error in a study that results in an incorrect estimate of the association between exposure and risk of an outcome.
    • Complete elimination of research bias is often impossible. Researchers aim to avoid bias in the study design and minimize its effect during analysis.
    • Bias is a result of an error in the design or conduct of a study.

    Types of Bias: Selection

    • Selection bias occurs when the way cases and controls are selected creates an apparent association that doesn't exist in reality.
    • Selection bias in case-control studies can occur if cases exposed to a substance are more likely to be chosen than those not exposed or vice versa.
    • Subjects in a study may not be representative of the overall population.
    • Examples include coffee drinking and pancreatic cancer, where stratification by drinking levels might mitigate selection bias.

    Types of Bias: Non-Response Bias

    • Non-response bias occurs when the response rate of a population with a particular disease is higher among those exposed than those not exposed.
    • A lower response rate among smokers in an asthma study via mail questionnaires could lead to bias.
    • Researchers try to collect data from non-respondents to mitigate this bias.

    Types of Bias: Information Bias

    • Information bias occurs when methods to collect information about study participants are inadequate and lead to incorrect exposure or outcome data.
    • Different levels of information given in the exposed and unexposed populations, or cases and controls, lead to incorrect conclusions.
    • Misclassifying exposure status can also cause information bias, especially if based on interviews without objective verification.

    Types of Bias: Information Bias- Recall Bias

    • Recall bias occurs when past exposures are more accurately recalled by some individuals than others, leading to bias in results.

    Types of Bias: Information Bias- Interviewer Bias

    • Interviewer bias occurs when interviewers subconsciously influence responses in different study groups. Blinding interviewers to the outcome can help reduce this.

    Types of Bias: Information Bias- Misclassification Bias

    • Misclassification bias occurs when participants' exposure or disease status is incorrectly categorized during the study.
    • This bias can be differential (misclassifying the exposure rates changes between groups) or non-differential (misclassifying rates don't change between groups).
    • The rate of misclassification may change between cases and controls during the study.

    Sources of Information Bias

    • Bias in abstracting records
    • Bias in interviewing
    • Bias from surrogate interviews
    • Surveillance bias
    • Recall bias
    • Reporting bias
    • Wish bias

    Impact of Bias on Estimation

    • Bias can underestimate or overestimate the RR/OR.
    • Researchers want to be more confident in their findings, especially if they underestimated the RR/OR.
    • Understanding how different factors might bias results of studies is important to drawing accurate conclusions.

    Evaluating Epidemiological Associations

    • Consider if the association could be observed by chance.
    • Evaluate the potential for bias.
    • Assess confounding variables that may account for observed outcomes.

    Confounding

    • Confounding variables (C) interfere with the observed association between a causal factor (A) and outcome (B).
    • They are associated with the putative causal factor and are causally associated with the outcome.
    • Cigarette smoking can be a confounding variable in studies connecting coffee consumption to pancreatic cancer.

    Controlling for Confounders

    • Research design strategies such as randomization, restriction, and matching can help control for confounders.
    • Analyze data by using stratification or multivariate analysis to adjust for confounding.
    • Example: Stratifying results by sex, age and other characteristics and adjusting for them.

    Types of Associations

    • Associations can be real (causal) or spurious (due to confounds).
    • An association between maternal smoking and low birth weight is causal.
    • An association between coffee drinking and pancreatic cancer might be spurious if confounded by smoking.

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    Related Documents

    Bias and Confounding Epidemiology PDF

    Description

    This quiz explores the concepts of bias and confounding in epidemiological research. It examines types of bias, with a focus on selection bias and its implications in case-control studies. Understand how bias affects research outcomes and the challenges in eliminating it.

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