Midterm

What is epidemiology?

The study of the distribution and determinants of health and diseases, morbidity, injures, disability, and mortality in populations 

Who are the pioneers and key figures in the history of epidemiology?

Hippocrates(460-377 BC), Thomas Sydenham (1624-1689), James Lind(1716-1794), Edward Jenner(1749-1823) 

Hippocrates (460-377 BC)

   was first to suggest relationships between health and enviormental factors, proposing the idea of four types of atoms influencing health. Fire , air , earth, water

Thomas Sydenham(1624-1689)

Collab w Robert Boyle, documented observations of diseases allowing him to identify and differentiate. Published Observationes Medicae. Catogerized fevers and removed heavy coverings from traditional treatments. Was scorned but he introduced diet, exercise, and fresh air 

James Lind (1716-1794)

Scottish naval surgeon, investigated scurvy using influence of time,place,weather,and diet. Observed how sailors were affected 4-6 months on the sea. He linked diet to disease, made clinical observations, experimental design, asking epidimiological questions, and population impacts

Edward Jenner (1749-1823)

notes that people who had cowpox did not get smallpox, he used cowpox lesions on another and inoculated a boy in 1796. This led to the first smallpox vaccine

Ignaz Semmelweis 1840s

doctor and epidemiologist, he investigated childbed fever, a deadly uterine infections affected mothers when doctors did not wash their hands during pelvic exams. By introducing hygiene, it was eradicated

John Snow

In London, boho street, he found the source of cholera. He plotted outbreaks and tracked the source to a sewage infested water source. Helped us understand disease transmission and shaped public health strategies. 

Louis Pasteur and Koch

Pasteur linked anthrax and rabies infections to eachother via dissections. He made a vaccine. Koch did the same and used photography and microscope to capture the germs Pasteur was studying about. He photographed many other bacterium improving our understanding. 

John Grant

Pioneered vital statistics in 1603 by keeping death certificates 

Framingham heart study

A cohort study that observed 5,209 participants between the ages of 30-62 , they identified factors that contributed to heart disease over time, it’s whag led us to look at BMI, cholesterol, bp, smoking, diet, and medical history

The Salk polio Vaccine Trial

Experimental study, he used a placebo and polio vaccine in childe r and it was up to 90% effective. 

The British doctors study in smoking and Lung cancer

Cohort study, study conducted by sending survey to British doctors and it proved that smoking made you have a higher risk of develooping lung cancer.

The bobo doll experiment

Experimental. Adults modeled aggression to a doll and the children recriprocated, in the absence of aggression they were fine 

The marshmallow test on delayed gratification

Experimental study, they placed a marshmallow in front of another child and were told they could get a second treat if they waited. Children that waited were proved to be more intelligent and have lower levels of substance abuses 

The Nurses Healfh Study

Cohort study, investigated contraceptive use, smoking , cancer and cardiovascular disease, and were able to conclude that these waste the biggest factors for chronic disease 

The Whitehall Studies in Social Determinants of Health

Cohort study, strong link between socioeconomic factors and health outcomes.

The Stanford prison experiment

Experimental studies, experiment where people were told to shock the prisoners and essentially demonstrated how social roles and situations can influence human behavior and become abusive or submissive 

The case control study on H.pylori on stomach Cancer

Infection increases risk of gastric cancer significantly. 90% of stomach cancer is from this.

Explain how epidemiology integrates knowledge and methods from a variety of fields (acute disease investigations, medicine, and others).

In the early 1900s, Edgar Sydenstricker enhanced morbidity statistics, Janet Lane-Claypon developed breast cancer study designs, Alice Hamilton advanced toxicology, and Wade Hampton Frost integrated epidemiology with biology and medicine.

Descriptive Inference

Summarizes disease patterns (e.g., "Diabetes prevalence in the U.S. is 10.5%").

Causal Inference

Determines if an exposure causes an outcome using observational and experimental studies (e.g., "Smoking causes lung cancer").

Predictive inference

Estimates future disease risk using statistical models (e.g., "High blood pressure increases heart disease risk by 30%").

Genaerazibility Inference

Assesses whether study findings apply to other populations

How has the field of epidemiology evolved in the modern world?

S. Miettinen, who advanced causal and statistical approaches, and Sir Austin Bradford Hill, who pioneered randomized clinical trials and causal criteria. Other influential statisticians include Jerome Cornfield (clinical trials, Bayesian inference), Joseph L. Fleiss (mental health statistics, kappa measure), Sander Greenland (meta-analysis, causal inference), Norman Breslow (case-control matched samples), Nathan Mantel (Mantel-Haenszel test and odds ratio), and William G. Cochran (experimental design and sampling techniques).

determinants

Biological (genetics, infections), Behavioral (smoking, diet), Environmental (pollution, climate), Social (income, healthcare access), and Healthcare factors (vaccination, treatment).

Distributions

By Person (age, sex, lifestyle), Place (geographic regions), and Time (trends, seasonal patterns).

Genomics

Identifies genetic risk factors, tracks disease mutations, and personalizes treatments (e.g., cancer genomics, pathogen sequencing).

Computer Science

Uses AI, machine learning, and big data analytics for disease modeling, outbreak prediction, and real-time surveillance (e.g., COVID-19 tracking, bioinformatics tools).

Internal Validity

Measures how accurately a study establishes a causal relationship between exposure and outcome within the study population. It depends on minimizing bias, confounding, and errors. Example: A well-controlled clinical trial proving a drug reduces blood pressure in a study group.

External Validation (Generalizibility)

Determines whether the study results apply to other populations, settings, or times. It depends on how representative the study sample is.Example: If the drug’s effectiveness in a clinical trial also applies to the general population.

A study needs strong _______ validity before it’s findings can be _____ valid.

Internal, external

Who introduced and produced the first known table of aggregated health data?

John Graunt in 1662. In his work, Natural and Political Observations Made upon the Bills of Mortality, Graunt analyzed London’s mortality records, identifying disease patterns and pioneering the field of epidemiology and vital statistics.

  What discovery related to Pasteur’s germ theory saved many women’s lives?

Proper handwashing and antiseptic techniques could prevent puerperal (childbed) fever saved many women's lives. Ignaz Semmelweis first demonstrated in the 1840s that handwashing with chlorinated lime significantly reduced maternal deaths in maternity wards.

Pasteur Germ Theory (1860’s)

provided scientific proof that microbes cause infections, leading to widespread adoption of antiseptic practices in hospitals, championed by Joseph Lister through surgical sterilization.

What is meant by the causal effect of exposure of disease in the study population?

Epidemiologists study patterns of diseases in order to figure out their causes. For example, if a disease is more prominent during a certain season, epidemiologists focus on environmental factors like contaminated water, insect activity, or foodborne exposures. It is also important for epidemiologists to compare disease rates across different regions to see how genetics, lifestyle, and the environment can impact health

What is the og definiton of disease?

lack of ease or comfort

How did the term disease evolve?

It wasn’t until the 14th century that disease. Chaucer used the word this way in “The Maniciple’s Prologue”

What is the etiology of disease?

The science and study of the cause of disease and their mode of transmission.

Describe the natural history of disease

 The first being the stage of susceptibility, which is basically the beginning of the likelihood that the host is developing an illness from an outside factor. The second stage is presymptomatic disease; this stage typically begins with the host being exposed to a disease of an accumulation of different factors large enough to be the stem point of a disease. The third stage is host to the incubation period and the latency period, which is basically when a disease is present but no symptoms are yet detected. The final stage of recovery, disability, or death, a point of exposure between the first two stages where changes within the body take place and are diagnosed. 

How are diseases classified in epidemiology?

Diseases which are congenital and hereditary, allergies and inflammatory diseases, degenerative diseases, metabolic diseases, and cancer. Congenital and hereditary are genetic diseases which are passed down, or even caused by an environment which the host grew up in. Allergies and inflammatory diseases are caused by reactions to a foreign object or substance that invades the body of the host. Degenerative diseases cause a low level of mental, physical, or moral stage than that of what is considered normal. Metabolic diseases are dysfunctions of certain organs that lead to disease states within the host's body. Cancer is a collective name that refers to a group of many diseases with one common characteristic being uncontrolled cell growth or loss of a cell’s ability to perform apoptosis.

What is the International Classification of Disease (ICD)?

Run by WHO, providing a “common language of disease” worldwide

What is the purpose of the ICD?

 Disease classification is done by the use of hospital records, death certificates, and other sources. It allows for the comparison of morbidity and mortality rates internationally. 1990

What type of diseases require mandatory reporting to health authorities?

If it causes serious morbidity or death, if it could spread, and if it can be controlled by public health intervention. They are also required to report diseases that are unusual. Medical professionals are required to report notifiable diseases. Different notifiable diseases have different mandated reporting time.

What are the social determinants of health (SDOH)?

Conditions in the environments in which people are born, live learn, work, play, worship, and age that affect a wide range of health, functioning, and quality-of-life outcomes and risks. Conditions (e.g., social, economic, and physical) in these various environments
and settings (e.g., school, church, workplace, and neighborhood) have
been referred to as “place”.

What is the key concept of “place”?

the patterns of social engagement and sense of security
and well-being are also affected by where people live. Resources that enhance quality of life can have a significant influence on population health outcomes.

Define health disparities and be able to provide examples.

A particular type of health difference that is closely linked with social, economic, and /or environmental disadvantage. Health disparities adversely affect groups of people who
have systematically experienced greater obstacles to health based on their racial or ethnic group; religion; socioeconomic status; gender; age; mental health; cognitive, sensory, or physical disability; sexual orientation or gender identity; geographic location; or other characteristics historically linked to discrimination or exclusion.

What is health equity in relation to health disparities?  

 Infant mortality, Maternal mortality
Childhood obesity vs. Premature death, Stroke-related mortality, Homicide

Explain the life-course perspective.

Chronic or severe stress during childhood in the
development of chronic disease later in life Dose-response association between the number of adverse events experienced in childhood and negative health outcomes

What ae some case studies shown in class that illustrate social determinants?

Whitehall studies, flint Water crisis, Hurricane Katrina, food deserts, covid-19 pandemic

Downstream Factors

Factors that are temporally and spatially close to health effects (and hence relatively apparent) but are influenced by upstream factors.

Upstream Factors

changes that lead to distinct outcomes (often temporally and spatially distant) through downstream factors

Social and Economic Policies

Minimum wage laws, paid sick leave, universal healthcare access.

Structural Inequities

Systemic racism, gender discrimination, educational disparities.

Environmental Conditions

Clean water, air pollution, housing quality.

What are some examples of upstream factors in health?

socioeconomic policies, structural Inequities, environmental, access to resources, Work/labor conditions.

Examples of downstream factors

medical treatment. health behaviors, clinical care access, rehab and recovery, health education

How are health outcomes influenced

Reduced care for POC’s and women. The conditions of the hospital are worse, short staffing,

epidemiological measurements

populations(fixed-survivors of war, dynamic-hospital patients)

What is the importance of measurment and what do they determine

Measurement is a cornerstone of epidemiology and epidemiologists must define “absence of health” or “disease” before measuring its frequency.

Fixed

membership is based on an event and is permanent, a type of population that epidemiologist study

Dynamic

membership is based on condition and is transitory, a tyype of population epidimiologists study

How does the World Health Organization define “health”?

A state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity.

Why have disease definitions changed over time?

Our knowledge of the diseases changes and evolves over time. We also associate more and more conditions with diseases over time.

 What are some diseases where the definition has changed over time?

AIDS, Autism

What are some consequences of changing disease classifications?

Distort perceptions in the incidence and prevalence of disease and result in artifactual improvements in outcomes. Distort perception of how successful clinicians are at treating disease. Rationale for changing disease classifications is based on false assumptions about the benefits of earlier detection of disease.

Define incidence rate, formula and the types of incidence rates? 

Incidence is the new cases of disease that develop in a defined population over a specified period of time. Incidence rate describes the rate of development of a disease in a group over a certain time period. Contains three elements: numerator = the number of new cases. Denominator = the population at risk. Time = the period during which the cases occur.

Numerator

all new and pre-existing cases during a given period of time.

Denominator

population during the same time period. Multiplied by 10^n

Period Prevalence

number of persons ill/average population

How do we use incidence rates?          

Incidence is most useful for evaluating the effectiveness of prevention programs. Research prefer to study new cases over existing ones if they are studying an exposure that led to developing the disease.

incidence

disease among those exposed a/(a+b)

prevelance

proportion of women who are fertile #women of reproductive age at some point/ total number of women at reproductive age at a point in time x100

Crude rates

numbers of deaths during agiven time period/ population from which the deaths occurred  x 100,000

crude birth rate

(# live births within a given period/population size at the middle of that period) x 1,000 population

General fertility rate

(# live births within a year/# of women aged 15-44 during the midpoint of the year) x 1,000 population

Infant mortality rate

(# of infant deaths among infants aged 0-365 days during the year/# live births during the year) x 1,000

Fetal death rate

(# fetal deaths after 20 weeks or more gestation/ # of live births + number of fetal deaths after 20 weeks or more gestation) x 1,000

Neonatal

(# infant deaths under 28 days of age/# of live births) X 1,000

Maternal mortality

(# deaths assigned to causes related to childbirth/# live births) x 100,000

Cause-specific rate

(mortality (or frequency of a given disease)/population size at midpoint of time period) x 100,000

time series

A sequence of repeated measurements taken at regular intervals over time, often used in epidemiology to study disease outbreaks and exposures.

Epidemic Curve

A histogram representing the duration of an epidemic, showing the incubation period and exposure pattern

Point Source Epidemic

A cluster of cases from a single exposure over a short period, resulting in a peaked epidemic curve. 

Continuous Source Epidemic

A prolonged exposure leading to a gradual increase, plateau, and decrease in cases over time. 

Longitudinal Data

Data collected from the same individuals over time, reducing variability compared to ecologic studies. 

Ecological Data

Group-level data that can introduce discrepancies due to population-level analysis. 

Age Effect

Changes in disease rates due to aging

Cohort Effect

Changes in disease rates influenced by birth year and shared experiences. 

period effect

Changes in disease rates affecting all age groups and cohorts due to external events (e.g., new vaccines, wars, economic shifts). 

Birth Cohort Effect

The impact of lifetime experiences on individuals' health based on their birth year. 

Time-Series Design

The measurement of numerical quantities over multiple time periods to analyze disease patterns. 

Secular Trend

Long-term changes in health patterns over years, which may be linear or nonlinear. 

Short-Term Trend-Brief

unexpected changes in health-related events occurring over hours, days, or months. 

Cyclic Pattern

Predictable, periodic increases and decreases in disease occurrence influenced by factors such as seasonality, migration, and school calendars

Seasonal Trend

A type of cyclic pattern that follows a predictable seasonal variation, influenced by environmental and behavioral factors. 

case

A set of  criteria (host,time, enviorment, agent)determines if someone has a disease or health condition

What is the importance of understanding the timing of disease occurrence and be able to offer planning preventive strategies?

Very important to prevent seasonal spikes-otherwise it could be worse