Intro to Epidemiology Flashcards
Define epidemiology.
The study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control of health problems
Define Mortality Rate.
A measure of the frequency of occurrence of death in a defined population during a specified interval (denominator population and specific time frame necessary).
Provide examples of possible denominators in epidemiology.
- Health board
- City
- Hospital
- Disease register
- Recruited to a study
Identify main types of timeframes in epidemiology ? Provide an example for each.
Person-time
(10 deaths per 10,000 person years which could be 10,000 people for 1 year, 5,000 people for 2 years, 2,000 people for 5 years)
n-year follow-up
(5-year mortality of 10 per 10,000 people)
Define incidence. How do we calculate this ?
Number of new cases
Incidence rate = (Number of new people with outcome over a time period x 100,000) / Total number of people in the group at risk
Define prevalence. How do we calculate this?
Proportion of population that has disease
Point prevalence rate (at a specified time, e.g. in 2010) = (Number of people with outcome at a point in time x 100) / Total number of people in the group
Period prevalence rate (over a specified period, e.g. lifetime) = (Number of people with outcome during a time period x 100) / Average number of people in the group
Distinguish prevalence and incidence.
INCIDENCE
• A rate or a proportion
• Useful for identifying causes of diseases
• Occurs, by definition, only in people without the disease
PREVALENCE
• A proportion
• Identifies disease burden
• Useful for planning services
• Depends partly on incidence
Describe how the following will affect prevalence/incidence ?
- Improved medication, procedures, rehabilitation
- Improved long-term management
- Increased diagnosis
Improved medication, procedures, rehabilitation, etc. –> Decreased prevalence
Improved long-term management –> Increased prevalence
Increased diagnosis –> Increased prevalence
What are the different patterns of outcome occurrence ?
- Sporadic: Occasional cases occurring irregularly.
- Endemic: Persistent background level of occurrence (low to moderate levels)
- Epidemic: Occurrence in excess of the expected level for a given time period
- Pandemic: Epidemic occurring in or spreading over more than one continent
Define outcome in the context of epidemiology, giving examples.
Any defined disease, state of health, health-related event or death
– Death – Hospitalisation – First diagnosis with a disease – Recurrence (e.g. cancer) – Quality of life – Surrogates (e.g. blood pressure, lung function, etc.)
Define exposures in the context of epidemiology.
Any factor that may be associated with an outcome of interest.
Identify the main categories of exposures, providing examples for each.
• Non-modifiable
– age, sex, genotype
• Modifiable
– smoking, weight, diet, alcohol consumption
• Interventions
– drug therapy
– surgery
– lifestyle advice
How do we calculate risk in epidemiology ?
(Number of outcomes in a group x 100) / Number of people in the group
How do we calculate Relative Risk ?
Relative risk (RR; Risk ratio) = Risk in exposed / Risk in unexposed
How do calculate Relative Risk Reduction (RRR) ?
(1 – Relative risk) x 100