Introduction to Epidemiology and Disease Dynamics

Epidemiology

"upon the people" Study of health and disease and the things that cause them in populations

Epidemiology applications

Multidisciplinary field including statistics, microbiology, law and policy, demography, history, genetics, clinical medicine, pathology, toxicology, and social and behavioral sciences

Epidemic

Occurrence in a community of cases of illnesses that can be health-related or behaviorally

Pandemic

Expanded out of original boundaries and goes international; Black Death, smallpox, covid

Distribution

How disease is spread through the population, including geographic (country, state, county) and demographic (age, sex and gender, race and ethnicity) aspects

Determinants

Factors that can change health for good or bad, directly or indirectly

Outcomes

Possible results that come from exposure to a causal factor or from preventative or therapeutic interventions

Hippocrates

First person to believe that disease had natural causes and argued that disease is from environmental factors, diet, and living habits; separated medicine from science

Pest houses

Places where people with smallpox would go to get better or die, most people were children; before vaccinations

Edward Jenner

Invented smallpox vaccine using materials from cowpox lesions, with the first patient being James Phipps

John Snow

Most accomplished anesthetist in Britain, showed that cholera is a waterborne disease by shutting down a contaminated water pump

Natural experiment

When a natural change occurs allowing for an experimental situation

Cholera outbreak

Caused by drinking water contaminated with waste

William Farr

One of the founders of medical statistics, promoted boiling water to prevent disease, and established a system for recording causes of death

Robert Koch

Founder of microbiology alongside Louis Pasteur, verified that human diseases are caused by specific organisms

Florence Nightingale

Founder of modern nursing, established the first secular nursing school and advocated for sanitary public housing

Data realization

Invented by Florence Nightingale, presenting graphs and numbers in an easy-to-understand way

Top causes of death

Shifted to chronic diseases like heart issues

Secular trends

Industrialization in societies, medical care improvements, and living condition improvements

Demographic transition

The shift from high birth and death rates

Epidemiologic transition

Shift from infectious diseases to chronic diseases as primary causes of morbidity

Community Health

Involves demographic and social factors, age and sex distribution, wealth and poverty, family structure, racial, ethnic, and religious composition, community infrastructure, policing, availability of health services, health-related outcomes, and environment

Disease Etiology

The things that cause disease

Risk

The probability of an individual developing a specified health outcome over a given period of time

Risk factor

An exposure associated with a disease, morbidity, mortality, or adverse health outcome

Risk assessment

A methodology providing quantitative measurements of health risk

Exposure

Any factor affecting or associated with a health outcome, ranging from political or social environment to the molecular level

Types of exposure

Include acute (short duration, generally not repeatable) and chronic (extended period, stable over time)

Time-vary exposures

Exposures that may occur intermittently or for an extended duration

Population focus

Epidemiology's focus on health at the population level

Descriptive epidemiology

Characterize the amount of distribution of health outcomes and measure their associations with exposures

Analytic epidemiology

test hypothesis regarding causal associations exposures and health outcomes; tells us what could work in solving health problems and what could

Population

a collection of people who share common observable variables

Sample

Subgroup selected from a population using a specific method

Probability

Gold standard for epidemiology, includes simple random, systematic, stratified, cluster, random digit dialing

Sample representativeness

how well characteristics of the sample correspond to the characteristics of the population from which the sample was chosen; sample more likely to look like your population

Data visualization

Representation of data through graphics like charts and plots and infographics

Histogram

Shows frequency of cases for categories of a quantitative variable

Choropleth map

Map using color to show variable levels in different areas

Incidence

Frequency of new cases of a disease in a population over time

Prevalence

Frequency of existing cases of a disease in a population; always a proportion never a rate

Rate

Type of ratio with a time component, includes crude rate

Case fatality rate

Rate of deaths due to a disease among those who contract it

Person variables

Factors like age, sex, socioeconomic status affecting health

FPL ratio

Federal poverty level ratio, varies across states

primordial prevention

conditions actions and measures that minimize health hazards and inhibit factors know to increase disease risk; making healthy living and social conditions

primary prevention

prevention before the occurrent of disease during pre pathogenesis; health promotion and specific protection against diseases

secondary prevention

early diagnosis and prompt treatment of disease and disability limitation; screening programs for early disease detection

Tertiary prevention

restoration of patient to a functional level after disease has occurred; rehabilitation programs for those affected by late sequela of disease

prepathogenesis

before disease occurs

determinants

typically called exposure; underlying factors that ultimately bring about disease

exposure

any factors that affects or is associated with a health outcome; exposures can be anything from political or social environment to the molecular level

acute exposure

occurs for a relatively short duration, generally do not repeat

chronic exposure

occurs for an extended period of time and stable over time; pollution, poverty, biological sex, race, etc.

time vary exposures

may occur intermittently or for an extended duration; level varies across the life course of an individual; diet, exercise, smoking, and alcohol consumption

distribution

differences in health or disease patterns in subgroups of the population

quantification

epidemiology uses statistics to describe the occurrence of health outcomes and measure their associations with exposures

crude rate

summary rate based on the entire population, does not account for any factors related to the disease such as the demographic make up of the population, difficult to interpret

descriptive epidemiology

provides a basis for generating hypotheses that we may test within analytic studies; prevention of disease with a goal to characterize the amount and distribution of health and disease within a population

case reports

account of one singular case that is worthy and health related; interesting or unusual

case series

collection of reports that are group consecutively listing common features; used for generating hypothesis, cannot study cause and effec; cannot assess disease frequency; characterizes averages for the disorder

age

most important factor to consider when describing occurrence of disease or illness

sex and gender

studies have shown sex differences in a wide scope of health outcomes; women tend to have higher rates of chronic illness and men have a higher risk of mortality

socioeconomic

descriptive term for a person's position or ranking in society; the social class gradient; sometimes formulated as a composite measure of the following dimensions

race

categorization of human based on shared physical or social qualities within a given society; "race is a social construct"

ethnicity

belonging to a population group or subgroup made up of people who share common cultural background

secular trends

gradual changes in the frequency of disease over long periods of time; increasing rates of obesity or decreasing rates of teen pregnancy

cyclical (seasonal) trend

regular changes in the frequency of a disease over a set period such as within a year or over several years; typically follow a pattern; often reflects seasonal trends

point epidemics

may indicate the response of a group of people in one place to a common source of infection to which they were exposed to at the same time

clustering

an unusual aggregation of health events group together in space or time

temporal clustering

grouping of cases in time

spatial clustering

concentration of cases of disease with a geographic

generalizability

the extent to which we can claim our findings inform us about a group larger than the one we studied; also known as external validity

census bureau

provides data that can be used to define the denominator in rates using; official estimates of total population size, subdivisions of the population by geographical area

vital records

vital events are death, brith, marriages, divorces, and fetal deaths

cause of death data accuracy

underlying causes can sometimes be unclear, unreported due to stigma, and some coroners can have little training

birth data accuracy

can be affected by the mother's failure to recall events during pregnancy, may miss conditions that were not detected at brith such as congenital anomalies

public health surveillance

the ongoing systematic collection, analysis, interpretation, and dissemination of health data; communicable and infectious diseases, and risk factors for chronic diseases

notifiable diseases

infectious and communicable diseases that pose a threat to the population

syndromic surveillance

investigational approach where health department staff monitor disease indicators in real time or near real time to detect outbreaks of disease earlier than would otherwise be possible with traditional public health methods

cross-sectional studies

examine the relationship between disease or other health-related characteristics and other variables of interest as they exist in a dinged population at one particular time

disease registries

a centralized database for collection of information about a disease; amyotrophic lateral sclerosis

SEER

source of epidemiologic information on the incidence and survival rates of cancer in the US