Epidemiology
The study of the occurrence, distribution, and determinants of health and disease in human populations
Occurrence
Describe the patterns of disease or health over time
Distribution
Frequency of a disease occurrence may vary from one population to another
Determinants
Factors or events that are capable of bringing about a change in health
Populations
Allows us to make the casual inferences regarding the association between a certain "exposure" and "outcome" using statistics
Study Population
Is the group of individuals of whom we make observations and collect data
Source Population
Is the group of individuals who are designated by personal, geographic, or temporal characteristics as eligible to be suspects in the study
Target Population
Is the group of individuals to which we would like to generalize our results
Why Epidemiology?
To understand the natural history of disease and the factors that influence its distribution. Describe. Explain. Predict.
Usual Frequency
Diseases typical occurrence at the same time, within the same population, and in the same geographic area
Endemic
Habitual presence of a disease in a geographic area or population group
Epidemic
Excessive occurrence of a disease. Outbreak
Pandemic
Worldwide epidemic
Surveillance
How we quantify the frequency of disease and determine whether or not an epidemic is taking place
3 Steps of Surveillance
1. Systematic collection of data pertaining to the occurrence of specific diseases. 2. Analysis and interpretation of these data. 3. Dissemination of disease-related information
Epidemic Threshold
The minimum number of cases (or deaths) that would support the conclusion that an epidemic is underway
Studying the history of health populations
Refers to the study of the past and future trends in health and illness
Secular Trends
Changes in disease frequency overtime
Disappearing Disorders
Conditions that were once common but are no longer present in epidemic form
Residual Disorders
Conditions for which the key contributing factors are largely known. Methods of control are not implements effectively
Persisting Disorders
Diseases for which there is no effective method of prevention, or no known cure
New epidemic disorders
Diseases that have increased frequency
Population Pyramid
Displays distribution of age and sex. Can help us predict the future of mortality from acute and chronic conditions
Population Pyramid Developing
Triangular distribution, high mortality rates from infections, high birth rates; fewer children survive into old age, morbidity and mortality associated with poverty
Population Pyramid Developed
Rectangular distribution, lower mortality rates from infections, greater portion of children survive into old age, longer life expectancy
Population Dynamics
Changes in the demographic structure of populations associated with such factors such as birth and death and migration
Demographic Transition
Shift from both high and low death rates found in agrarian societies to lower birth and death rates found in developed countries
Epidemiologic Transition
Shift in the pattern of morbidity and mortality from infectious and communicable diseases to chronic, degenerative disease
Etiology
Having to do with the causes of disease
Hill's Strength
#1 The larger the relative risk, the stronger the evidence is for causality
Hill's Repetition
#2 The association between exposure and disease has been observed by different persons in different places, circumstances, and time
Hill's Specificity
#3 One exposure, one disease
Hill's Temporality
#4 Time sequence, the exposure must precede the disease
Hill's Biological Gradient
#5 Evidence of a dose -response relationship
Hill's Plausibility
#6 Biologically plausible
Hill's Coherence of Explanation
#7 The association must not conflict with what is already known about the natural history and biology of disease
Hill's Experiment
#8 The strength in experimental trials in human subjects is the ability to randomize the factor being studied
Hill's Analogy
#9 Similarities between other exposures and disease
Risk Factor
Exposure that is associated with a disease
Prepathogenesis Period
Occurs before the exposure
Pathogenesis Period
Occurs after the exposure
Primary Prevention
Occurs during prepathogenesis period. Seeks to minimize health hazards to lower the occurrence of disease
Secondary Prevention
Occurs during pathogenesis period. Screening and early diagnosis
Tertiary Prevention
Occurs during late pathogenesis period. Reduce limitations or disability and improve symptoms