Scientific Foundations: Epidemiology Flashcards
Incidence rate
An epidemiologic term that describes the occurrence of new disease or injury per unit of time among persons at risk
Incidence rate numerator
Includes only new cases of disease during a given time period
Incidence rate denominator
Includes everyone at risk of developing the disease during that period
Incidence measures…
The probability (or risk) of developing disease
Use of incidence rates
Tracking trends in the development or resolution of disease
Prevalence
An epidemiologic term that describes the proportion of the population with the condition at a given point in time or during a given time period
Prevalence numerator
Includes new and existing cases
Prevalence denominator
Includes all who are at risk for developing the disease, including those who have it
Prevalence measures…
The current burden of disease
Prevalence uses
Measuring and projecting health care and health resource needs
Applications of epidemiologic research
- Controlling infectious diseases
- Controlling the effects of chemical hazards
- Understanding genetic susceptibility to disease
- Understanding the effects of nutritional status
- Linking pathogens to specific disease processes
- Identifying risk factors for illness and injury
Evaluation of —– among exposures and health outcomes is central to epidemiology
Associations
Criteria to evaluate causality based on an observed association include the following…
- The strength of the association
- Consistency of the association
- Temporality of the association
- Dose-response relationship
- Plausibility of association
Strength of the association
Refers to the degree of correlation between the exposure and the disease
Consistency of the association
- Similar findings result across several studies of the same association
- Conclusions similar despite use of different study designs, under different conditions and in different populations
Temporality of association
-demonstrates that the cause precedes the effects
Temporality cannot be evaluated with a —— study
Cross sectional
Dose response relationship
As the degree of exposure increases, the risk for developing outcome increases
Lack of a dose response relationship does not rule out a —–
Causal relationship
Plausibility of the association
- Association is consistent with a plausible biologic explanation
- Sometimes there is not enough scientific evidence to draw a conclusion about biologic plausibility
Knowledge required to determine biologic plausibility
- Natural history of the disease
- Results of animal experiments
- Results of other laboratory experiments
Population based health outcome data includes:
- Census data
- Vital statistics
- National health surveys
- Disease and death registries
Census data is obtained from
US Census Bureau
Vital statistics are obtained from
US Census Bureau
National health surveys are obtained from
National Center for Health Statistics
Examples of population based national health surveys
- National Health and Nutrition Examination surveys
2. National Health Interview Survey
OSHA recordable illnesses and injuries are captured through mandatory reporting systems maintained by…
Bureau of Labor Statistics
Examples of exposure data
- Air monitoring data
2. Biomarkers of exposure
Exposure data can be obtained from….
Exposure registries
Examples of exposure registries
- Heavy metal exposure
- Certain pharmaceuticals
- Needle stick injuries
Exposure status is sometimes estimated indirectly from the following information:
- Occupational history
- Dietary history
- Location of residence
Key terms in comparisons of rates
- Relative risk
- Odds ratio
- Attributable risk
Relative risk
Aka rate ratio
A measure of the relationship between two incidence rates, that of the exposed and that of the unexposed population
Odds ratio
A good estimate of relative risk, but is derived from case control or cross-sectional studies
Attributable risk
A measure of the difference between two rates, one for the exposed and one for the unexposed populations. It describes the increased amount of risk attributed to the exposure
Crude rates
Based on the actual numbers of events for a given time period but do not reflect true differences in risk amount subgroups in a population
Characteristic-specific rates
Allow one to compare rates for similar subgroups of two or more populations
Examples of characteristic-specific rates
Age-specific
Gender-specific
Adjusted (or standardized) rates
Reflect population differences by taking into consideration the distribution of important characteristics that may affect risk
Example of adjusted rate
Age-adjusted rate
The crude rates of lung cancer in a population will not reflect….
The fact that older individuals are at higher risk for lung cancer
To look at the association between smoking and lung cancer, it would be appropriate to compare…..
Crude rates of lung cancer in groups of s,pokers and nonsmokers who differ in she distribution
Rates of lung cancer could be computed for age-specific groups to…..
Examine differences in lung cancer rates by age
The age-adjusted rates of lung cancer in the swing and nonsmoking groups could be compared to…..
Examine the question of an association between smoking and cancer
Epidemiology
The study of the distribution and determinants of health related states or events in specified populations, and the application of this study to the control of health problems
