Disease Frequencies Flashcards
Define epidemiology and its importance in public health:
Epidemiology is the measurement of exposure and outcome, and the relationship between them
- identifies risk factors for disease
- tracks disease patterns over time
- assess effectiveness of public health policies
Define exposure and outcome and how they relate to epidemiology:
Exposure - any factor that might influence disease development
Outcome - the health-related event or disease being studied
Epidemiology assesses whether an exposure increases the risk of an outcome
Distinguish Between Descriptive and Analytical Epidemiology
Descriptive:
- used to answer the question of who, where, and/or when in relation to an outcome or exposure
- hypothesis generating
- Incidence, prevalence, mortality rates are the measures used
Analytical:
- Identifies causal relationships between exposure and disease
- used to answer the question of why and/or how an outcome or exposure occur
- used for hypothesis testing
- Risk ratio, odds ratio, attributable risk are the measures used
Define incidence, mortality rate and prevalence as measures of disease occurrence:
Incidence:
- measures new cases of a disease over time in a population at risk
- Formula: Incidence Rate = (New cases) ÷ (Population at risk)
- Useful for studying disease outbreaks and identifying risk factors
- incidence rate = No. of new cases of disease in defined population over given time period/ Total person-time at risk during same period (known as theoretical incidence rate
Prevalence:
- measures the total number of cases (new + existing) in a population at a specific time
- Formula: Prevalence Rate = (Total cases) ÷ (Total population)
- useful for assessing disease burden and healthcare planning
Mortality rate:
- measures the number of deaths due to a specific disease per population size
- formula: (Deaths from disease) ÷ (Total population)
Describe the different types of exposure:
Acute (e.g., radiation exposure after an accident).
Chronic (e.g., long-term smoking leading to lung disease).
Single vs. Multiple exposures (e.g., diet, stress, pollution in heart disease).
Differentiate between direct and indirect relationships
Direct - exposure leads straight to an outcome e.g., lead poisoning → cognitive decline
Indirect - exposure affects intermediate factors, which then cause the disease
e.g, obesity → hypertension → stroke
Describe the risk ratio as a measure of association:
Compares the risk of disease in exposed vs. unexposed groups
Formula: RR = (Risk in exposed) ÷ (Risk in unexposed)
Interpretation:
RR = 1 → No association.
RR > 1 → Exposure increases risk
RR < 1 → Exposure is protective
Example - RR of 2.0 for smoking and lung cancer means smokers are twice as likely to develop lung cancer
used in cohort studies and clinical trials as it represents actual probability
Describe the odds ratio as a measure of disease association:
Compares the odds of disease in exposed vs. unexposed groups
Used in case-control studies when risk cannot be directly measured
Formula: OR = (Odds of disease in exposed) ÷ (Odds of disease in unexposed)
Example - an OR of 3.0 means exposed individuals are 3 times more likely to have the disease
Describe attributable risk as a measure of disease association:
Measures how much risk is directly due to an exposure.
Formula: AR = (Risk in exposed) - (Risk in unexposed)
Example: If 30% of lung cancer cases occur in smokers vs. 5% in non-smokers, AR = 25%.
Describe Controlling for Age in Epidemiology:
Disease rates differ by age, requiring age-standardization to compare populations fairly
Methods:
Crude rates: Unadjusted, may be misleading.
Age-specific rates: Break down data into age groups.
Age-standardized rates: Adjust for age differences to allow fair comparisons.
