Risk, Rate and Odds
TLDRIn this informative video, Greg Martin clarifies the often-confused concepts of risk, rate, and odds in public health and epidemiology. He explains that risk is the probability of a health outcome within a specific time frame for a defined population, calculated as new incidents over the population at risk. Rate, similar to risk, is new cases divided by person-time, accounting for varying study durations and participant contributions. Odds, on the other hand, compare the likelihood of an event to non-events, with values greater than one indicating a higher likelihood of the event. The video uses relatable examples to distinguish these terms, emphasizing their importance in understanding health data.
Takeaways
- 📈 Risk is the probability of a person getting sick or experiencing a health outcome within a certain time frame.
- 🔢 To calculate risk, a defined population at risk, a specific time period, and the count of new incidents of the health issue are needed.
- 📊 Risk can be expressed as a simple fraction, like 3 out of 10 people, or as a percentage (e.g., 30%).
- 🔄 Rate is similar to risk but accounts for the varying time each individual is at risk by using person-time as the denominator.
- 👥 Person-time is the cumulative time each participant spends at risk in a study, which adjusts for participants who leave or die during the study.
- 🎲 Odds are the ratio of the number of events to the number of non-events, or the probability of an event happening divided by the probability of it not happening.
- 🎯 At low incidence rates, risk and odds are very similar and can be almost indistinguishable.
- 🔢 When odds are greater than one, the event is more likely to occur than not; when odds are less than one, the event is less likely to occur.
- 🌟 The difference between odds and risk becomes more apparent at higher incidence rates.
- 📚 The video is part of a series on public health concepts, with the next video focusing on the difference between case-control and cohort studies.
- 👋 The presenter encourages viewers to subscribe to the Global Health YouTube Channel and engage with the content through comments and notifications.
Q & A
What is the definition of risk in the context of public health and epidemiology?
-Risk is the chance of a person getting sick or experiencing some other health outcome within a specific time period.
What are the three requirements for calculating risk?
-To calculate risk, one needs a defined population at risk, a defined period of time during which the risk is considered, and the count of new incidents of the disease or health state of interest during that time period.
How is the risk calculated for a group of 10 people where 3 develop cancer within a year?
-The risk is calculated as 3 (number of new cancer cases) divided by 10 (total population), which equals 30%.
What is the difference between rate and risk?
-Rate is similar to risk, but instead of dividing by the total population, it is calculated by dividing the number of new cases by the person-time, which accounts for the time each individual contributes to the study.
How does the person-time calculation work in the context of rate?
-Person-time is the cumulative time each individual spends in a study. It accounts for participants who may drop out or die during the study, ensuring a more accurate rate calculation.
What does the term 'odds' mean in statistics?
-Odds refer to the ratio of the number of events to the number of non-events, or the probability of an event occurring divided by the probability of it not occurring.
How can you interpret odds in terms of likelihood?
-If the odds are more than one, the event is more likely to happen than not. If odds are less than one (between 0 and 1), the event is less likely to happen than not. If odds are exactly one, the event is as likely to happen as not.
What is the difference between risk and odds in a scenario with low incidence?
-In low incidence scenarios, risk and odds are very similar and almost indistinguishable from each other.
How does the difference between risk and odds become more apparent?
-The difference between risk and odds becomes more apparent when the incidence of the event is higher.
In the cinema sneezing example, what is the risk and odds when 55 people sneezed during the film?
-The risk is 55% (55 sneezing individuals out of 100), and the odds are 1.2 (55 who sneezed divided by 45 who didn't sneeze), indicating it's more likely for someone to sneeze than not in that scenario.
What are the next steps for further understanding of these concepts?
-The next steps include watching another video on understanding the difference between a case-control and a cohort study, which are methodologies used in epidemiology.
How can one stay updated with the Global Health YouTube Channel?
-By subscribing to the channel, turning on the Bell notification for updates, and engaging with the content through comments and feedback.
Outlines
📚 Introduction to Risk, Rate, and Odds
This paragraph introduces the concepts of risk, rate, and odds, which are essential in public health and epidemiology. Greg Martin explains that risk is the probability of a person getting sick or experiencing a health outcome within a certain time frame. To calculate risk, a defined population, a specific time period, and the number of new incidents of the health issue are needed. The explanation is given using the example of 10 people over a year, where 3 develop cancer, leading to a 30% risk. The paragraph sets the stage for a deeper understanding of these concepts and their applications in health studies.
Mindmap
Keywords
💡Risk
💡Rate
💡Odds
💡Population
💡Incidence
💡Person-time
💡Prevalence
💡Systematic literature review
💡Meta-analysis
💡Epidemiology
Highlights
Greg Martin discusses the concepts of risk, rate, and odds in public health and epidemiology.
Risk is defined as the chances of a person getting sick or experiencing a health outcome within a certain time frame.
To calculate risk, a defined population, a specific time period, and the count of new incidents of the health outcome are needed.
Risk calculation is demonstrated with an example of 3 out of 10 people developing cancer in a year, resulting in a 30% risk.
Rate is similar to risk but involves dividing the number of new cases by 'person time', accounting for varying study durations and participant drop-outs.
Odds are the number of events divided by the number of non-events, or the probability of an event happening divided by not happening.
Odds are more intuitive when the incidence of an event is higher, showing a clearer distinction from risk.
In a cinema with 100 people, the risk of one person sneezing is 1%, while the odds are calculated as 1 to 99.
With 55 people sneezing in the cinema, the risk is 55%, and the odds are 1.2, indicating a higher likelihood of sneezing than not.
The video aims to clarify the often-confused concepts of risk, rate, and odds for better understanding in public health contexts.
The channel is sponsored by Nested Knowledge, a platform supporting systematic literature review and meta-analysis.
The presenter encourages viewers to watch the next video on the difference between case-control and cohort studies.
The video concludes with a call to action for viewers to subscribe, engage with notifications, and provide feedback in the comments.
Greg Martin emphasizes the importance of understanding these concepts for those in the field of global health.
The video provides practical applications of risk, rate, and odds calculations in real-world scenarios, such as a sneezing incident in a cinema.
The distinction between risk and odds is crucial for accurate interpretation of health data and epidemiological studies.
Transcripts
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