L22 (T1): Thinking about populations in time: incidence & cohort studies
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What is the meaning of incidence?

  • Incidence measures the total number of cases of a specific outcome in a population at a designated time.
  • Incidence measures the proportion of cases of a specific outcome in a given population at a designated time.
  • Incidence measures the frequency of cases of a specific outcome in a population at a designated time.
  • Incidence measures the rate of new cases of a specific outcome in a population over a defined period of time. (correct)

    • How is prevalence calculated?

  • Prevalence = number of people with outcome * number of people who could have outcome.
  • Prevalence = number of people with outcome - number of people who could have outcome.
  • Prevalence = number of people with outcome / number of people who could have outcome. (correct)
  • Prevalence = number of people with outcome + number of people who could have outcome.

    • What does prevalence measure?

  • Prevalence measures the frequency of new cases of a specific outcome in a population over a defined period of time.
  • Prevalence measures the rate of new cases of a specific outcome in a population over a defined period of time.
  • Prevalence measures the total number of cases of a specific outcome in a population at a designated time.
  • Prevalence measures the frequency of cases of a specific outcome in a population at a designated time. (correct)

    • What is the calculation of prevalence expressed as?

    <p>Percentage</p> Signup and view all the answers

    What does incidence measure?

    <p>Incidence measures the rate of new cases of a specific outcome in a population over a defined period of time.</p> Signup and view all the answers

    What is the denominator required for the calculation of prevalence?

    <p>Number of people who could have outcome</p> Signup and view all the answers

    How is prevalence expressed as a proportion per unit of population?

    <p>700 of every 1000 people</p> Signup and view all the answers

    What is the formula for calculating relative risk in a cohort study?

    <p>RR = incidence of outcome among exposed / incidence of outcome among non-exposed</p> Signup and view all the answers

    In a cohort study, what does a relative risk (RR) of 1.5 indicate?

    <p>Risk of outcome 50% higher in exposed than unexposed group</p> Signup and view all the answers

    What is the relative risk (RR) when the risk of outcome is 20% lower in the exposed group than the non-exposed group?

    <p>RR = 0.8</p> Signup and view all the answers

    In the context of the given cohort study, what does 'incidence' refer to?

    <p>Number of new cases of a condition in a given time period</p> Signup and view all the answers

    What is the formula for calculating prevalence?

    <p>Prevalence = incidence x outcome duration</p> Signup and view all the answers

    What type of study is used to measure incidence?

    <p>Cohort study</p> Signup and view all the answers

    What does the relative risk (RR) quantify in a cohort study?

    <p>Exposure-outcome association</p> Signup and view all the answers

    What is the primary purpose of a cohort study?

    <p>To compare the health of groups with and without a specific exposure</p> Signup and view all the answers

    What is the key advantage of cohort studies in relation to confounding variables?

    <p>Exposures are measured before outcomes, reducing the impact of confounding</p> Signup and view all the answers

    What is the numerator for the incidence rate?

    <p>The number of new events</p> Signup and view all the answers

    How is incidence calculated?

    <p>Number of new cases in a given time period divided by the population at risk</p> Signup and view all the answers

    What does prevalence depend on?

    <p>Incidence of an outcome and the time between onset and recovery or death</p> Signup and view all the answers

    Why is understanding incidence crucial for healthcare providers, researchers, and policymakers?

    <p>It aids in understanding diseases, their risk factors, and outcomes</p> Signup and view all the answers

    What can affect the incidence of diseases like diabetes?

    <p>Changing diagnostic criteria, screening, management, and record-keeping practices</p> Signup and view all the answers

    What does the denominator represent in the calculation of incidence?

    <p>The total population at risk</p> Signup and view all the answers

    What does understanding disease trends, geographical differences, and informing public health interventions rely on?

    <p>Incidence</p> Signup and view all the answers

    What is the formula for calculating relative risk in a cohort study?

    <p>$\frac{\text{Incidence in exposed group}}{\text{Incidence in non-exposed group}}$</p> Signup and view all the answers

    What does a relative risk of 1 indicate in a cohort study?

    <p>No difference in the risk of developing the outcome between the exposed and non-exposed groups</p> Signup and view all the answers

    What is a potential weakness of cohort studies?

    <p>Potential for losses to follow-up</p> Signup and view all the answers

    Which type of cohort study focuses on studying outcomes that have already occurred?

    <p>Retrospective cohort study</p> Signup and view all the answers

    What does relative risk (RR) measure in a cohort study?

    <p>The risk of developing an outcome in the exposed group compared to the non-exposed group</p> Signup and view all the answers

    What kind of data sources can be used for cohort studies?

    <p>Mortality registers, hospital/medical records, census data, and survey data</p> Signup and view all the answers

    What is a strength of cohort studies compared to cross-sectional studies?

    <p>Offer more protection against confounding</p> Signup and view all the answers

    In a cohort study, what is the key difference between incidence and prevalence?

    <p>Incidence measures the rate of new cases of a disease within a specific time period, while prevalence measures the total number of existing cases of a disease at a specific point in time</p> Signup and view all the answers

    What is a potential limitation of cohort studies in relation to rare diseases?

    <p>They may require large sample sizes and long follow-up periods to observe enough cases of the rare disease</p> Signup and view all the answers

    What is the primary difference between an incidence rate and an incidence proportion?

    <p>Incidence rate considers person-time at risk, while incidence proportion does not account for varying lengths of follow-up</p> Signup and view all the answers

    Study Notes

    Using Cohort Studies to Measure Incidence

    • Cohort studies can be used to measure incidence by comparing the occurrence of outcomes in exposed and non-exposed groups
    • Types of cohort studies include prospective, retrospective, and studies focusing on specific population subsets
    • Strengths of cohort studies include providing evidence of cause-effect relationships and calculating relative risk
    • Weaknesses of cohort studies include potential for losses to follow-up and vulnerability to confounding variables
    • Cohort studies offer more protection against confounding than cross-sectional studies
    • Secondary sources of cohort study data include mortality registers, hospital/medical records, census data, and survey data
    • Relative risk (RR) is used to compare the risk of developing an outcome in the exposed group to that in the non-exposed group
    • The formula for calculating relative risk involves comparing the incidence of the outcome among the exposed to the incidence among the non-exposed
    • The strength and direction of association in relative risk can indicate the risk factor for the outcome
    • An example of calculating relative risk involves comparing the all-cause mortality in patients newly diagnosed with type 2 diabetes, with and without established cardiovascular disease
    • The relative risk in this example is 1, indicating no difference in the mortality risk between the two groups
    • Cohort studies can provide valuable insights into the incidence of outcomes and the impact of exposures, aiding in decision-making for public health and clinical interventions.

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    203 Lecture 2 Theme 1 Incidence CB 2023.pptx

    Description

    Test your knowledge of using cohort studies to measure incidence with this quiz. Explore the types, strengths, weaknesses, and applications of cohort studies, as well as the calculation and interpretation of relative risk.

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