Epidemiology Flashcards
(26 cards)
What is epidemiology?
Studies the patterns of disease frequency in the human population
Focuses on factors that cause disease, prevent disease, prolong life with a disease, and improve health status
What are modifiable risk factors?
Risk factors that can be reduced or controlled by intervention, thereby reducing the probability of the disease
Ex. physical inactivity, tobacco use, excessive alcohol use, unhealthy diet
What are non-modifiable risk factors?
Cannot be reduced or controlled
Ex. age, gender, race, family history (genetics)
What are some common measures of disease frequency/vital statistics?
Prevalence
Incidence
Birth rate
Mortality rate
What is prevalence?
The number of existing cases/total population at risk
Expressed as a percentage or n
*number of existing cases at a specific time
What is point prevalence?
How many have the disease at this point in time
What is period prevalence?
Estimate of prevalence over a period of time
What is incidence?
Number of new cases occurring during a specified time period
Can be interpreted as the risk of one randomly selected individual bein newly diagnosed with a disease in a specified time period
What is cumulative incidence?
Proportion of individuals who become diseased (injured) during a specified period of time
Number of new cases during period/total population at risk
What is incidence rate?
Length of follow-up period not uniform for all participants
Calculate with person-time as denominator
Accounts for those who had to drop out of the study due to incidence
How is prevalence related to incidence?
Prevalence = incidence x duration
What is birth rate?
Number of live births during year/total population at midyear
What is mortality rate?
Number of deaths during specified time period/population at midpoint
Are crude mortality rates adjusted?
No
Adjusted mortality rates are calculated for strata within a risk factor
What are some adjusted mortality rates?
Age-specific mortality rates
Sex-specific
Country/region-specific
What are some common measures of association?
Relative risk ratio
Odds ratio
Attributable risk
Absolute risk reduction/NNT
What is event rate?
The proportion of subjects in a group whom a defined event is observed
The experimental (exposed) event rate is the event rate in the exposed group (smokers)
The control (unexposed) event rate is the event rate in those not exposed (non-smokers)
What is relative risk?
Likelihood that someone exposed to a risk factor will develop the disease as compared to those not exposed
Incidence in the exposed/incidence in the unexposed
What is relative risk ratio?
RRR of 2.0 means that the outcome occurred 2x more often in those exposed than those not exposed
What are the odds?
Reflects the likelihood that a particular event will take place
1-to-5 for rolling a six on a fair die
What is odds ratio?
Represents the odds that an outcome will occur given a particular exposure, compared to the odds of an outcome occurring in the absence of that exposure
May reflect the odds of an experimental patient suffering an event relative to the odds of a control patient suffering an event
An OR of 2.1 means that cases (diseased) were 2.1x more likely to have been exposed than were control (unexposed) subjects
Should odds ratios only be used in case-control studies?
Yes
When is the odds ratio a good estimate of relative risk?
When the disease being studied occurs at a low frequency: <10%
Only option to calculate risk in case control studies (cannot calculate incidence)
What is attributable risk?
The proportion of disease that can be attributed to a specific exposure
Risk of those exposed-risk of those not exposed
