Chapter 2

Essential Public Health Foundations

To excel on the Certified in Public Health (CPH) exam, your grasp of foundational public health sciences must be unshakable. These core disciplines, epidemiology, biostatistics, environmental health, and health policy form the backbone of every public health professional's toolkit. Mastery here not only primes you for exam success but positions you to make impactful, evidence-based decisions in your career.

In this chapter, we dissect each foundational area with precision and depth, progressing logically from fundamental concepts to complex applications. Expect to gain mental models, mnemonic devices, and real-world perspectives designed to solidify your expertise and sharpen your exam strategy.

Core Public Health Sciences

Introduction to Epidemiology and Biostatistics Principles

Epidemiology: The Science of Disease Patterns and Prevention

Epidemiology is the cornerstone of public health-a rigorous discipline dedicated to understanding the distribution and determinants of health and disease in populations. It is your analytic lens for identifying risk factors, designing interventions, and evaluating health outcomes.

• Key Epidemiological Measures:

• Incidence: The count of new cases within a specified time frame. It reflects disease risk.
• Prevalence: The proportion of a population affected by a disease at a specific point in time. Useful for assessing disease burden.
• Mortality and Morbidity Rates: Mortality captures deaths, morbidity encompasses disease incidence and prevalence.

• Study Designs:

Understanding the strengths, limitations, and applications of each study design is non-negotiable:

• Descriptive studies: Cross-sectional surveys, case reports - snapshot of health status.
• Analytical studies: Case-control, cohort, and randomized controlled trials (RCTs) establish associations and causality.
• Ecological studies: Group-level analysis, useful for generating hypotheses.

• Bias and Confounding:

These are formidable exam traps.

• Selection bias: Distorted sample due to non-random participation.
• Information bias: Errors in data collection, e.g., recall bias.
• Confounding: Third variables that distort the exposure-disease relationship. Master strategies to identify and control confounding, including stratification and multivariate analysis.

• Measures of Association:

• Relative Risk (RR): Ratio of incidence in exposed vs. unexposed groups.
• Odds Ratio (OR): Odds of exposure among cases vs. controls, commonly in case-control studies.
• Attributable Risk (AR): The proportion of disease incidence attributed to exposure.

Mnemonic for Study Designs:
"D-CAR" - Descriptive, Case-control, Analytical (cohort), Randomized controlled trials.

Biostatistics: The Language of Public Health Data

Biostatistics empowers you to interpret health data rigorously and critically. Its vocabulary, formulas, and techniques unlock the stories behind numbers.

• Descriptive Statistics:

• Central tendency: Mean, median, mode, summarize data distributions.
• Variability: Range, variance, standard deviation quantify data spread.

• Probability and Distributions:

• Understand the normal distribution curve and its properties-68-95-99.7 rule.
• Distinguish between discrete and continuous variables.

• Inferential Statistics:

• Hypothesis testing fundamentals: null and alternative hypotheses.
• p-values: Probability that observed results occurred by chance. Interpret with context-p < 0.05 typically indicates statistical significance.
• Confidence intervals (CI): Range within which the true population parameter lies with specified confidence (usually 95%).

• Common Statistical Tests:

• t-test: Compare means between two groups.
• Chi-square test: Test association between categorical variables.
• ANOVA: Compare means across multiple groups.
• Regression analysis: Examine relationships between dependent and independent variables.

• Power and Sample Size:

Understand the balance between type I (false positive) and type II (false negative) errors and their impact on test power.

Expert Insight: Top scorers don't just memorize formulas-they internalize the "why" behind each measure and test, enabling rapid, intuitive problem-solving under exam pressure. Visualize epidemiologic relationships as real-world cause-and-effect chains, and treat biostatistical concepts as your toolkit for precision analysis.

Environmental Health Basics and Social Determinants

Environmental health and social determinants bridge biology, behavior, and environment-highlighting how external factors shape population health.

Environmental Health: Protecting Populations from Hazards

Environmental health focuses on the identification, evaluation, and control of physical, chemical, and biological hazards.

• Key Environmental Hazards:

• Chemical: Lead, asbestos, pesticides, air pollutants (PM2.5, ozone).
• Physical: Noise, radiation, temperature extremes.
• Biological: Vector-borne pathogens (malaria, Zika).

• Exposure Pathways:

• Inhalation, ingestion, dermal contact.
• Understand the concept of dose-response relationship: increased exposure leads to increased effect, often with a threshold.

• Environmental Epidemiology Principles:

• The exposure assessment process is vital-accurately measuring who is exposed, how, and for how long.
• Investigate environmental justice issues: vulnerable populations often face disproportionate exposures.

• Risk Assessment and Management:
  Four steps to evaluate environmental hazards:

• Hazard Identification
• Dose-Response Assessment
• Exposure Assessment
• Risk Characterization

• Regulatory Frameworks:
  Familiarize yourself with major public health laws and agencies:

• EPA (Environmental Protection Agency)
• Clean Air Act, Clean Water Act
• OSHA (Occupational Safety and Health Administration)

Social Determinants of Health: The Roots of Health Inequities

The social determinants of health (SDOH) are conditions in the environments where people live, learn, work, and play powerfully influencing health outcomes.

• Core Domains:

• Economic Stability (income, employment)
• Education Access and Quality
• Healthcare Access and Quality
• Neighborhood and Built Environment
• Social and Community Context

• Health Equity vs. Equality:
  Understand the critical distinction:

• Equality means everyone gets the same resources.
• Equity means resources are distributed based on need to achieve equal outcomes.

• Examples of SDOH Impact:

• Food deserts increasing risk of chronic diseases.
• Residential segregation linked to differential exposure to environmental hazards.
• Education levels strongly correlate with health literacy and outcomes.

• Frameworks and Models:

• The WHO Commission on Social Determinants of Health Framework - illustrates pathways from social conditions to health inequities.
• Life Course Approach: Examines how early-life social factors influence lifelong health trajectories.

Health Policy, Management, and Communication Overview

Public health is not only about science-it is also about systems, policies, leadership, and communication that translate knowledge into action.

Health Policy Fundamentals

• Policy Cycle:

• Agenda setting Policy formulation Adoption Implementation Evaluation.
  Understanding this cycle prepares you to analyze how public health initiatives are developed and modified.

• Types of Policies:

• Laws (statutes and regulations), programs, funding decisions.
• Differentiate between public policies (government-driven) and organizational policies (within health agencies).

• Health in All Policies (HiAP):

A multidisciplinary approach embedding health considerations across sectors like transportation, housing, and education to promote holistic health outcomes.

Health Management: Systems and Leadership

• Key Concepts:

• Organizational structure: Hierarchical vs. flat models, roles and responsibilities.
• Resource allocation: Balancing budget, personnel, and materials to optimize public health interventions.
• Quality improvement: Continuous cycles such as Plan-Do-Study-Act (PDSA)...