40 Questions
What does the incidence rate of a disease include?
New cases, population at risk, and interval of time
Why is it important to monitor the incidence rate of a disease?
To decide if an epidemic is in progress
What is the purpose of calculating the incidence rate of myocardial infarction (MI) in a community?
To calculate the individual risk of MI
What is the unit of measurement for the incidence rate of a rare disease?
Per 100,000 person-years
What is another term for the number of new cases of a disease?
Incidence
Why is it important to know the number of existing cases of a disease?
To measure the burden of disease
What is an example of when incidence rate is particularly useful?
When monitoring epidemics regarding aetiology and prevention
What is the formula to calculate the incidence rate of a disease?
Number of new cases / total population
What is the prevalence rate per 1,000 people in the given population?
53 per 1,000
What is the relationship between incidence and prevalence?
Higher incidence rate always leads to higher prevalence rate
What happens to the prevalence rate if the incidence rate increases?
It increases
What is the formula to approximate the prevalence of a disease?
P = I x L
What does a high incidence rate in the exposed and a low incidence rate in the unexposed suggest?
The exposure may be a cause of the disease
What happens to the prevalence rate if more patients are cured?
It decreases
What is the incidence rate ratio (IRR) used for?
To compare incidence rates between groups
What happens to the prevalence rate if more patients die from the disease?
It decreases
Why is there a spurious association between living in Liverpool and a high risk of skin cancer?
Due to the difference in age distribution between Liverpool and the rest of the UK
What is an example of a confounding variable in the context of lung cancer?
Age
What is the purpose of Age-Sex Standardisation in epidemiology?
To eliminate the effect of age and sex on disease incidence
What does the Standardised Mortality Ratio (SMR) calculation help to establish?
What the rate ratio for two populations would be if they had the same age-sex structure
Why is age a problem in epidemiology?
Because it is a confounding variable that can affect the search for modifiable risk factors
What is the meaning of confounding in epidemiology?
The situation in which an association between an exposure and an outcome is observed due to the influence of a third unobserved factor
What is the purpose of confounding in epidemiology?
To explain the observed association between an exposure and an outcome
What is an example of a confounder in the relationship between living in Liverpool and skin cancer deaths?
Age
What is the alternative way to express the risk of death when comparing two treatments?
The new treatment halves the risk of death compared to the old treatment.
What is the purpose of comparing risk on different treatments?
To compare the effects of treatment
What type of systematic variation is considered a nuisance?
Variation in age and sex
What is the limitation of targeting prevention at particular age-sex groups?
Age and sex are not useful for prevention
What is the rate ratio for most diseases comparing old and young people?
> 1.0
What does the mortality rate ratio of 5.0 indicate about skin cancer mortality in Liverpool compared to the rest of the UK?
The mortality rate is 5 times higher in Liverpool than the rest of the UK
What is the possible cause of skin cancer mortality in Liverpool according to the text?
Sunbathing
What is the purpose of comparing the mortality rate of skin cancer in Liverpool to the rest of the UK?
To identify the cause of skin cancer
What is the primary purpose of Standardised Mortality Ratio (SMR)?
To account for age-sex confounding in mortality rates
What does an SMR value of 100 indicate?
The same risk of mortality in the study population as in the standard reference population
What is the difference between incidence and prevalence?
Incidence measures new cases, while prevalence measures existing cases
What is the purpose of incidence rate ratio (IRR) comparisons?
To search for treatment effects or causes of disease
What is a common application of incidence in epidemiology?
All of the above
What is the purpose of prevalence in epidemiological studies?
To estimate disease burden
What is a potential limitation of incidence rate ratio (IRR) comparisons?
They can be a nuisance due to confounding
What is the main advantage of using SMR?
It gives a single summary measure of disease corrected for age-sex confounding
Study Notes
Disease Measures
- Incidence: the number of new cases of a disease over a specific period of time
- Prevalence: the proportion of people affected by a disease at a specific point in time
Components of Incidence
-
- New cases
-
- Population at risk
-
- Interval of time
Uses of Incidence
- Epidemiology: to monitor the effect of prevention programs, compare exposure to potential hazards, and measure the burden of disease
- Clinical trials: to evaluate the effectiveness of treatments
- Disease surveillance: to track the spread of infectious diseases and monitor for outbreaks
Example of Incidence Rate Calculation
- Myocardial infarction (MI) example: Incidence rate = 50 new cases / 5,000 population = 10 per 1,000 people
Relationship between Incidence and Prevalence
-
Prevalence is influenced by:
- Incidence rate
- Death rate
- Cure rate
- Formula: P ≈ (I x L), where P = Prevalence, I = Incidence, and L = Length of disease
Useful Variations in Risk of Disease
- Comparing incidence rates: to identify potential causes of disease and evaluate treatment effects
- Incidence Rate Ratio (IRR): used to compare incidence rates between groups with different levels of exposure
Nuisance Variations in Risk of Disease
- Systematic variations in risk: can be a nuisance when not related to the disease under study
-
Examples:
- Age and sex as determinants of health
- Skin cancer mortality rate in Liverpool vs. rest of UK (confounded by age)
Confounding
- Definition: a situation where an association between exposure and outcome is influenced by a third unobserved factor (confounder)
- Example: the relationship between place of residence and risk of death from skin cancer is confounded by age
Age-Sex Standardisation and Standardised Mortality Ratio (SMR)
- Purpose: to account for age-sex confounding
- SMR calculation: compares observed mortality in a study population with expected mortality if a standard reference population's age-sex specific rates were applied
- Interpretation: SMR > 100 indicates higher risk in the study population
Learn about the concept of incidence and prevalence in epidemiology, specifically in the context of cystic fibrosis in the Kurdistan Region, Iraq.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
