NURS 8310 – Epidemiology and Population Health
Walden University DNP Program
Week 1 Study Notes: Foundations of Epidemiology & Population Health Primary Textbook Reference
Gordis, L. Epidemiology (6th ed., 2014 or latest). Elsevier. Focus: Chapters 1–3 (Introduction to Epidemiology, Measures of Disease Frequency, Descriptive Epidemiology).
Core Learning Objectives for Week 1 Define epidemiology and trace its historical development.
Differentiate key terms: epidemiology vs. clinical medicine, population health vs. public health.
Identify and describe the three core functions of epidemiology.
Calculate and interpret basic measures of disease frequency (incidence, prevalence, mortality rates).
Apply the person–place–time framework to describe disease patterns.
1. Definition of EpidemiologyClassic definition (Gordis, based on Last, 2001):
“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.”
Key elements:Distribution — Who is affected? Where? When? (person, place, time)
Determinants — Why are some people affected and others not? (risk factors, causes)
Population — Focus is on groups, not individuals (contrast with clinical medicine)
Application — Use findings to prevent/control disease (public health action)
Modern emphasis (CDC, WHO):
Epidemiology now includes social determinants, health equity, chronic disease, global health threats, and policy translation.
2. Brief History of EpidemiologyAncient roots: Hippocrates (400 BCE) – observed environmental influences on disease (“Airs, Waters, Places”).
17th–18th century: John Graunt (1662) – first life tables using London Bills of Mortality → birth of vital statistics.
19th century – foundational era:William Farr (1839) – established systematic registration of causes of death; introduced classification of diseases.
John Snow (1854) – cholera outbreak in Soho, London; removed Broad Street pump handle → classic epidemiologic investigation (natural experiment).
20th century – modern epidemiology:1948 Framingham Heart Study – cohort design for cardiovascular risk factors.
Doll & Hill (1950s) – case-control and cohort studies linking smoking to lung cancer.
1980s–present: HIV/AIDS, chronic disease epidemiology, molecular/genetic epidemiology, big data, precision public health.
Milestones in nursing: Lillian Wald (Henry Street Settlement, 1893) – early public health nursing; Florence Nightingale – use of statistics to improve hospital outcomes.
3. Core Functions of EpidemiologyEpidemiology serves three primary functions (CDC/WHO framework):Surveillance Ongoing, systematic collection, analysis, interpretation, and dissemination of health data.
Purpose: Detect outbreaks, monitor trends, evaluate interventions.
Examples: Notifiable disease reporting, syndromic surveillance, National Notifiable Diseases Surveillance System (NNDSS).
Investigation (Outbreak/Epidemic Investigation) Rapid response to unusual health events.
Steps (CDC 10-step model): Prepare, establish existence of outbreak, verify diagnosis, construct case definition, find cases, perform descriptive epidemiology, develop hypotheses, evaluate hypotheses (analytic studies), refine hypotheses, implement control measures, communicate findings.
Example: E. coli O157:H7 outbreak linked to spinach (2006).
Research Hypothesis-driven studies to identify causes, risk factors, and effectiveness of interventions.
Designs: descriptive (hypothesis generation), analytic (hypothesis testing), experimental (intervention trials).
4. Population Health vs. Public Health vs. Clinical MedicineAspect
Population Health
Public Health
Clinical Medicine
Focus
Health outcomes of groups + determinants
Organized community efforts to prevent disease, promote health
Diagnosis & treatment of individuals
Unit of analysis
Defined populations/communities
Communities, states, nations
Individual patients
Goal
Improve overall health & equity
Prevent disease, prolong life, promote health
Cure disease, relieve suffering
Key metrics
Health disparities, life expectancy, DALYs
Vaccination coverage, outbreak control
Patient outcomes, survival rates
Example question
Why is diabetes prevalence higher in low-income neighborhoods?
How can we increase HPV vaccination rates?
How do we manage this patient’s HbA1c?
Population health (newer term) emphasizes upstream determinants (SDOH), equity, and cross-sector collaboration (healthcare + education + housing).
5. Measures of Morbidity & MortalityMorbidity Measures Incidence — New cases in a population over a specified time. Incidence rate = (new cases / population at risk) × multiplier (usually 1,000 or 100,000 per year)
Incidence proportion (cumulative incidence) = new cases / initial disease-free population
Prevalence — Existing cases (old + new) at a point in time or period. Point prevalence = (existing cases / total population) × 100
Period prevalence = (cases during interval / average population) × 100
Key relationship: Prevalence ≈ Incidence × Duration of disease
(High prevalence can result from high incidence, long duration, or both.)Mortality Measures Crude mortality rate = (total deaths / total population) × 1,000 per year Affected by age structure of population.
Specific rates — Age-specific, cause-specific, sex-specific, etc.
Age-adjusted (standardized) rate — Removes effect of different age distributions when comparing populations (direct or indirect method).
6. Person–Place–Time Framework (Descriptive Epidemiology)Used to characterize disease occurrence and generate hypotheses.Person Age, sex/gender, race/ethnicity, socioeconomic status, occupation, behaviors (smoking, diet), genetics.
Example: Higher lung cancer mortality in males historically (smoking patterns); now converging due to changing behaviors.
Place Geographic variation (local, regional, global).
Examples: Malaria endemic in sub-Saharan Africa; higher obesity in U.S. South (food deserts, culture); radon exposure and lung cancer clusters.
Time Secular trends (long-term), seasonal variation, cyclic (epidemic waves), point-source outbreaks.
Examples: Seasonal influenza peaks in winter; COVID-19 waves; declining cardiovascular mortality since 1970s (smoking reduction, statins).
Epidemic curve (time axis): point-source (common exposure), propagated (person-to-person), intermittent.Quick Reference TablesIncidence vs. PrevalenceMeasure
Numerator
Denominator
Time frame
Interpretation
Incidence
New cases
Population at risk
Specified
Risk of developing disease
Prevalence
Existing cases
Total population
Point or period
Burden of disease in population
Crude vs. Specific vs. Adjusted RatesType
Adjusts for age?
Use case
Crude
No
Overall burden in one population
Specific
Yes (by stratum)
Compare within age/sex groups
Age-adjusted
Yes
Fair comparison between populations
High-Yield Week 1 Tips for DNP StudentsMemorize formulas for incidence, prevalence, RR, OR (will be tested repeatedly).
Practice interpreting age-adjusted rates (why are they needed?).
Be ready to discuss how epidemiology differs from clinical reasoning.
Use person-place-time when describing any health problem in discussions/assignments.
Recommended Week 1 ActivitiesRead Gordis Chapters 1–3.
Review CDC Principles of Epidemiology (free self-study course).
Explore CDC Wonder or countyhealthrankings.org for real data.
Prepare for discussion by choosing one disease and describing its person-place-time pattern.
