2025 POPLHLTH111 Lecture 5 - Full Slides

Module 1 Overview

• L2: Epidemiologic Thinking

  • Epidemiology is based on understanding the relationship between the numerator (cases), denominator (population at risk), and time.

• L3: Common Design Features in Epidemiological Studies

  • Use of GATE (Group, Age, Time, Exposure).

• L4 & L5: Measures of Disease Frequency

  • Incidence: Number of new cases occurring in a defined population during a specific time period.

  • Prevalence: Total number of existing cases in a population at a specific point in time.

• L6 & L7: Measures That Compare Disease Frequencies

  • Risk Ratios: Comparison of the probability of an event occurring in two groups.

  • Risk Differences: Difference in risk between two groups.

• L8: Non-Random Error (Bias) in Epidemiological Studies

  • Use of RAMBOMAN to evaluate measurement accuracy.

• L9: Random Error in Epidemiological Studies

  • Assessment via 95% confidence intervals to determine measurement accuracy.

• L10: Different Features and Uses of Epidemiological Studies

  • Each study type serves unique purposes in public health research.

Case Study: Asthma Epidemic in New Zealand

• Epidemic: Occurrence of disease above normal levels; Pandemic: Epidemic across multiple countries.

• Investigating an Epidemic: Use incidence and prevalence measurements to understand asthma deaths.

Lecture Objectives

• Explain when to measure incidence vs. prevalence.

• Describe methods for defining numerators in prevalence measurement.

Anatomy of Asthma

• Affected Areas:

  • Bronchioles, Nose, Throat, and Trachea: Major parts of the respiratory system affected by asthma.

  • Diaphragm: Main muscle in the respiratory function.

• Asthma Attacks: Involve swelling and constriction of the bronchioles leading to wheezing.

Asthma Treatments

• Inhalers: Common method to deliver asthma medications.

• Bronchodilators: Medications that relax bronchial muscles.

• Steroids: Used to reduce inflammation in bronchioles.

Calculating Asthma Occurrence

• Measuring the incidence of fatal asthma attacks is comparatively easier than non-fatal attacks due to frequent occurrence.

Measurement Challenges

• Incidence of Fatal Asthma Attacks: Easier to measure when individuals have passed away from asthma.

• Hospital Visits: Incidence is easier to calculate as they represent occurrences of attacks requiring medical attention.

• Non-Fatal Attacks: Difficult due to the intermittent nature of asthma attacks and the prevalence of mild symptoms.

Prevalence Measurement Limitations

• Measuring the prevalence of asthma attacks at a single point in time may not reflect the true situation since many may not be experiencing attacks at that moment.

• Criteria for Defining Asthma: Often based on the occurrence of moderate or severe attacks within a specific timeframe.

Questionnaire for Asthma Assessment

• Questionnaire administration assesses the history of asthma symptoms and attacks.

Epidemiological Findings

• After analyzing asthma prevalence and incidence in New Zealand versus Australia, conclusions were drawn regarding the higher asthma death rates in New Zealand, linked to treatment differences.

• Notable findings have attributed higher asthma death rates to specific drugs (Fenoterol), utilized during an asthma epidemic in the 1980s.

Trends and Implications

• Graphs and data illustrate the effects of inhaler usage on asthma death rates from the 1960s.

• Investigations into the relationship between drug dosage and asthma mortality rates led to broader understandings of asthma management practices.

Conclusion

• Epidemiological Research: Critical for understanding disease patterns and for public health interventions aimed at reducing asthma mortality.