Epidemiology Basics and Disease Frequency

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Questions and Answers

What is the primary reason an observed association may not indicate a causal effect?

  • Lack of statistical significance
  • Random sampling errors
  • The presence of confounding variables (correct)
  • Insufficient sample size

How do measures of association relate to exposure and outcome variables?

  • They estimate future health outcomes
  • They quantify the relationship strength and direction (correct)
  • They identify the most affected demographic
  • They measure the cost of exposure

What type of comparison is often involved in identifying causes of disease?

  • Comparing groups based on treatment received
  • Comparing age groups within the same exposure level
  • Comparing geographic regions with differing health policies
  • Comparing disease incidence between exposed and unexposed groups (correct)

What do we estimate by measuring disease incidence across different exposure groups?

<p>The association between exposure and outcome (D)</p> Signup and view all the answers

What does an association between exposure and outcome imply, if not controlled for confounding?

<p>A potential misinterpretation of data (B)</p> Signup and view all the answers

What does incidence proportion specifically measure in a closed population?

<p>The proportion of the population that becomes diseased within a specific timeframe (B)</p> Signup and view all the answers

Which of the following is NOT a consideration when calculating incidence proportion?

<p>Identification of exposed individuals (C)</p> Signup and view all the answers

What has the greatest impact on the accuracy of incidence proportion?

<p>The follow-up time and loss to follow-up (D)</p> Signup and view all the answers

How is incidence proportion calculated?

<p>By dividing the number of new cases by the size of the population at risk over time (D)</p> Signup and view all the answers

What term describes the proportion of a closed population at risk that becomes diseased within a period of time?

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

In what situation is incidence proportion most accurately used?

<p>When the follow-up time is short with little loss to follow-up (D)</p> Signup and view all the answers

What does the term 'population at risk' refer to in the context of incidence proportion?

<p>A defined group that is susceptible to the disease (C)</p> Signup and view all the answers

Which measurement provides the best estimate of average risk over time in a defined population?

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

What is the primary focus of descriptive epidemiology?

<p>To characterize distributions of health and diseases (C)</p> Signup and view all the answers

Which of the following best defines incidence in epidemiology?

<p>The number of new occurrences of a disease in a population over a specified time period (B)</p> Signup and view all the answers

What distinguishes closed populations from open populations in epidemiology?

<p>Closed populations only experience deaths, while open populations can gain or lose members (D)</p> Signup and view all the answers

Which aspect does etiologic or analytic epidemiology primarily assess?

<p>The effect of exposures on disease occurrence (C)</p> Signup and view all the answers

Why are demographic and geographic patterns in disease occurrence important?

<p>They inform public health programming and identify causal mechanisms (B)</p> Signup and view all the answers

What type of study collects data at a single point in time?

<p>Cross-sectional study (A)</p> Signup and view all the answers

Which of the following factors could be considered an exposure in epidemiology?

<p>Vaccination status of individuals (A), Genetic predisposition in a population (B)</p> Signup and view all the answers

What is a primary aim of epidemiology?

<p>To obtain a valid and precise estimate of disease frequency and patterns (C)</p> Signup and view all the answers

What is an average causal effect of treatment A on outcome Y in a population?

<p>Pr[Y a=1 = 1] ≠ Pr[Y a=0 = 1] (C)</p> Signup and view all the answers

In the context of causality, what does a sufficient cause imply?

<p>It initiates a sequence of events resulting in an effect. (D)</p> Signup and view all the answers

Which factor is not associated with population-level causality?

<p>Smoking behavior (A)</p> Signup and view all the answers

What distinguishes causation from association in epidemiological terms?

<p>Causation implies a difference in risk under two exposure values. (C)</p> Signup and view all the answers

What must be true for a causative relationship to exist between an exposure A and an outcome Y?

<p>There must be an observed association. (C)</p> Signup and view all the answers

Regarding exposure A and outcome Y, which statement about association is accurate?

<p>Association does not infer causation. (C)</p> Signup and view all the answers

Which level of causality is concerned with pathological changes in the lung after tobacco exposure?

<p>Organ-level (D)</p> Signup and view all the answers

Which of the following statements is true regarding the necessary cause of enteric illnesses?

<p>There is generally one necessary cause for enteric illnesses. (A)</p> Signup and view all the answers

What does a risk ratio greater than 1 indicate?

<p>Increased risk of outcome (A)</p> Signup and view all the answers

What is the primary purpose of calculating a rate ratio?

<p>To compare disease incidence (A)</p> Signup and view all the answers

When the risk ratio equals 1, what does this imply?

<p>There is no risk difference between groups (B)</p> Signup and view all the answers

If an incidence rate ratio (IRR) is less than 1, what conclusion can be drawn?

<p>Reduced rate of outcome in the exposed group (A)</p> Signup and view all the answers

Which of the following correctly describes the calculation of risk in the exposed group?

<p>Calculated as D+ | E+ (A)</p> Signup and view all the answers

Which measure specifically refers to time at risk in its calculation?

<p>Rate ratio (A)</p> Signup and view all the answers

What does an incidence rate ratio (IRR) equal to 1 mean?

<p>Null difference in rate (A)</p> Signup and view all the answers

In the context of disease frequency, what do 'D+' and 'D-' represent?

<p>Individuals with and without the disease respectively (D)</p> Signup and view all the answers

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Study Notes

Disease Occurrence

  • The study of the distribution and causes of disease, health, and other events in populations is known as epidemiology.
  • Descriptive epidemiology focuses on characterizing the distribution of health, disease, and exposures in a defined population, including differences over time.
  • Etiologic or analytic epidemiology examines the effects of exposures, such as possible causes, on the occurrence of disease.
  • Exposure can be understood at multiple levels, including genetic, personal (demographics, behaviours, medical history, environment), and societal (neighbourhood SES, national income inequality).
  • One aim of epidemiology is to estimate disease frequency and identify patterns that vary with time, place, and population subgroups.

Disease Frequency

  • Population is a group of people who share characteristics or meet criteria for membership at a specific time.
  • Measures of disease occurrence are observed in populations at or over a specific time (cross-sectional or longitudinal, respectively).
  • Closed populations add no new members and only lose members due to death.
  • Open populations experience both gains and losses.
  • Incidence refers to the number of new occurrences of a condition or disease in a population over a specific time period.
  • Incidence proportion (also known as cumulative incidence, risk, or attack rate) is the proportion of a closed population at risk that becomes diseased within a given time period.
  • Incidence proportion is a measure of average risk (probability of developing the disease during the specified time period) for individuals in a closed population.
  • Incidence rate is a measure of the number of new cases in a defined population per unit of time.
  • Prevalence is the number of cases of a disease present in a population at a specified time (also known as point prevalence).
  • Prevalence is influenced by incidence and duration of the disease.

Causality

  • Causality can be studied at multiple levels – population, individual, organ, cellular, or molecular.
  • Association doesn't imply causation; merely that two variables may be related, but not necessarily causally linked.
  • Confounding occurs when an unmeasured factor affects both exposure and outcome, falsely suggesting a causal relationship.

Measures of Association

  • Measures of association quantify the strength and direction of the relationship between exposure and outcome variables.
  • Risk Ratio (RR) is the incidence of disease in the exposed group divided by the incidence of disease in the unexposed group.
  • RR>1 indicates an increased risk, RR=1 indicates no difference in risk, and RR<1 indicates a decreased risk.
  • Rate Ratio (IRR) compares the incidence rate of disease in the exposed group to the incidence rate in the unexposed group.
  • IRR>1 indicates an increased rate, IRR=1 indicates no difference in rate, and IRR<1 indicates a decreased rate.

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