Public Health Science : Chapter 1-5 [ 302 ] EXAM REVIEW

Population

• Requires more than one individual

• These individuals share one or more common characteristics

• People in a particular place—-with discernible geopolitical boundaries

• A set of commonalities—-one or more characteristics shared by members of the population

Health

• A state of complete physical, mental, and social well-being

• Not merely the absence of disease or infirmity

• A fundamental right of every human being

• Regardless of race, economic or social condition, religion, or political belief

Public health

• Is the science of protecting and improving the health of families and communities through the promotion of healthy lifestyles, research for disease and injury prevention, and detection and control of infectious diseases.

• To promote and protect the health of people and the

  communities where they live, learn, work, and play.

Public health : Centers for Disease Control and Prevention (CDC) Foundation Definition

Public health is the science of protecting and improving the health of families and

communities through the promotion of healthy lifestyles, research for disease and injury

prevention, and detection and control of infectious diseases

Public Health

The science and art of preventing disease, prolonging life, and promoting health through organized societal efforts (Winslow definition).

Population Health

The health outcomes of a group of individuals, including the distribution of such outcomes within the group

Population Health Science

The study of the conditions, mechanisms, and interventions that shape health outcomes across population groups.

WHO Health Definition

A state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity (1948)

Edwin Chadwick (Mid-1800s, UK)

Spearheaded London's sanitation movement. Linked clean water supply and sewage removal directly to economic productivity, arguing that poor health caused economic decline

Lemuel Shattuck (1850, US)

Published the landmark survey in Massachusetts cross-tabulating mortality by age, sex, occupation, socioeconomic status, and geographic location, establishing vital statistics systems.

20th-Century Achievement [ 1900-1999 ]

• Vaccinations

• Motor-vehicle safety improvements

• Safer workplaces & Occupational injury drops

• Control of infectious diseases through sanitation

• Decline in deaths from heart diseases & stroke

• Safer and healthier foods

• Healthier mothers and babies

• Family planning and contraceptive access

• Fluoridation of drinking water

• Recognition of tobacco use as a health hazard

21st Century Achievements (2001–2010 Expansion)

• Vaccine-preventable disease reduction

• Prevention and control of infectious diseases

• Tobacco control (policy & tax measures)

• Maternal and infant health advances

• Motor vehicle safety enhancements

• Cardiovascular disease prevention

• Occupational safety milestones

• Cancer prevention & early detection

• Public health preparedness & emergency response

• Childhood lead poisoning prevention

THE DALY EQUATION:

DALY = YLL + YLD

YLL (Years of Life Lost):

Measures premature mortality.

Formula: = N × L (where N = number of deaths, L = standard life expectancy at age of death).

YLD (Years Lived with Disability):

Measures non-fatal health loss and reduced functioning.

Formula: ____= I × DW × D (where I = incident cases, DW = disability weight [0 to 1], D = duration).

Level of Prevention : Primordial

Timing/Focus: Far Upstream (Societal/ Environmental)

Primary Objective: Eliminate environmental or social conditions that express risk factors

Key Example: National policies banning trans fats or mandating clean air regulations.

Level of Prevention :Primary

Timing/Focus: Pre-pathogenesis (Before Disease Onset)

Primary Objective: Prevent initial disease occurrence or adoption of elevated risk behaviors

Key Example: Routine childhood immunizations, smoking cessation programs for healthy youth

Level of Prevention :Secondary

Timing/Focus: Subclinical Disease (Early Detection)

Primary Objective: Detect and treat asymptomatic disease early to reduce prevalence and impact.

Key Example: Mammograms, Pap smears, routine blood pressure screening, colonoscopies

Level of Prevention : Tertiary

Timing/Focus: Clinical Disease (Post-Diagnosis)

Primary Objective: Slow disease progression, prevent target organ damage, and rehabilitate

Key Example:Cardiac rehabilitation post-infarction, physical therapy, glycemic control in diabetes.

Universal Prevention

Applied to the entire general population regardless of individual risk

Ex. Water Fluoridation

Selective Prevention

Targeted at specific subgroups exhibiting above-average risk factors

Ex. Exchange for IV drug users

Indicated Prevention

Targeted at high-risk individuals exhibiting early detectable warning signs or biological markers

Ex. Pre-diabetes programs

Sensitivity

Probability that a diseased person screens positive

• [True Positives / (True Positives + False Negatives)]

• High sensitivity minimizes false negatives

Specificity

Probability that a non-diseased person screens negative

• [True Negatives / (True Negatives + False Positives)]

• High specificity minimizes false positives.

WHO Screening Criterion

Screening is only justified if there is established scientific proof that treatment initiated during the asymptomatic/subclinical stage yields superior outcomes compared to treatment started after symptoms emerge

Health Equality

Distributing identical resources equally to everyone, regardless of existing baseline advantages or disadvantages.

Health Equity

Providing customized resources according to specific social needs so that everyone has a fair and just opportunity to attain their full health potential.

Health Disparities / Inequities

Avoidable, unfair, and systematic differences in health outcomes driven by social, economic, or geographic disadvantage

Ex.Black Americans having 2x higher stroke mortality than White Americans

The 5 Social Determinants of Health [ Domains ]

• Economic Stability

• Education Access & Quality

• Healthcare Access & Quality

• Neighborhood & Built Environment

• Social & Community Context

Economic Stability

Poverty, employment, food security, housing stability, commercial pressure.

Education Access & Quality

High school graduation, literacy, early childhood education, higher education access

Healthcare Access & Quality

Health insurance coverage, health literacy, culturally competent provider availability.

Neighborhood & Built Environment

Quality housing, access to transportation, clean water/air, walkability, crime exposure

Social & Community Context

Social cohesion, civic participation, exposure to discrimination, structural racism.

Socio-Ecological Model

Illustrates that health behaviors are not purely individual choices but are shaped across nested levels of influence

Individual / Intrapersonal

• Biological factors

• Age

• Sex

• Genetic susceptibility

• Personal knowledge

• Personal habit

Interpersonal / Social Network

• Family Dynamics

• Peer Influences

• Partner

• Support

• Social modeling

Organizational / Institutional

• Workplace Environments

• School Policies

• Local Community Organizations

Community / Neighborhood

• Built Environments

• Neighborhood deprivation

• Local availability of healthy food

Societal / Policy

• National laws

• Federal excise taxes

• Commercial marketing regulations

• Structural forces

Critical Period Mode

Exposure during a specific developmental window causes permanent structural or functional changes

Ex. Maternal smoking during fetal development causing low birth weight

Sensitive Period Model

Exposure during a specific window has a disproportionately strong effect, though impact can still occur at other times

Ex. Peer smoking initiation during adolescence

Chain of Risk Model

A sequential domino cascade where one exposure leads directly to another risk factor

Ex. Adolescent smoking leading to alcohol use, leading to illicit drug dependence

Accumulation of Risk Model

The total cumulative burden of multiple exposures over time gradually damages physiological systems

Ex. Decades of smoking leading to noncommunicable disease mortality

Life Course Epidemiology

Studies how early exposures influences chronic disease risk decades later

WHO Screening Principles

1. The condition must be an important health problem with a known natural history.

2. There must be a recognizable latent or early asymptomatic stage.

3. A suitable, acceptable, and accurate screening test must exist.

4. Crucial Rule: Evidence must prove that early treatment before symptom onset produces superior health outcomes compared to treatment started after symptoms arise.

Interventions are systematically categorized into four distinct levels…

• Primordial

• Primary

• Secondary

• Tertiary

Epidemiological Transition:

The historic shift in population mortality from communicable/infectious diseases (1900) to noncommunicable diseases (NCDs) such as heart disease, cancer, and diabetes.

Global Disparities:

• In low-income countries, 6 of the top 10 leading causes of death remain infectious/communicable (e.g., lower respiratory infections, diarrheal diseases).

• In high-income countries, 9 of 10 leading causes are NCDs

US Mortality Trends:

In 2021, COVID-19 emerged as the 3rd leading cause of death (>400,000 deaths). Life expectancy in the US began declining in 2014, driven primarily by the opioid epidemic (>121,000 overdose deaths in 2021)

Social Ecological Perspective

Our health is produced through a variety of levels: from an individual’s family members and friends, social networks, neighborhoods and cities, countries, and global influences

Life Course Perspective

Our health is produced throughout the sequential phases of our life. The social ecological and life course dimensions create a useful matrix for understanding the health of populations.

Social Ecological Perspective : Model Graph

Life Course Perspective : Model Graph

Chains of Risk [ Lecture Notes ]

Involve exposures that occurs in series

• This may involve a domino-like sequence risks

• Sometimes risk chains escalate, setting the individual on course toward a serious a fatal outcomes

• Applied to describe cascades of health-promoting behaviors

Chains of Risk : Model

Accumulation of Risk [ Lecture Notes ]

Cumulative exposures or shocks occurring exposures throughout the life course increase the risk of disease later in life irrespective of timing

Accumulation of Risk : Model

1900s Leading Causes of Death

1. Influenza and Pneumonia

2. Tuberculosis

3. Gastrointestinal Infections

4. Heart Disease

5. Stroke

2000-2010s Leading Cause of Death

1. Heart Disease

2. Cancer

3. Unintentional Injuries

4. Chronic Lower Respiratory

5. Stroke

2020s Leading Cause of Death

1. Heart Disease

2. Cancer

3. COVID-19

4. Unintentional Injuries

5. Stroke

Level of Prevention : Quaternary

Prevent harm from over-medicalization or unnecessary interventions.

Ex.Matching glucose control levels to specific patient populations to avoid overmedication.

The Early Days of Public Health:

• Human societies employed hunting and gathering as their predominant subsistence strategies.

• Survival of early humans depended on mobility in search of water and sustenance.

• At a most basic level, a primary indicator of health was staying alive.

Mid-1800s London: Edwin Chadwick advocated for improving living conditions in order to improve health….

• He argued that improved health would improve productive output and reduce social costs.

• The tie-in to public health was his proposal to provide clean water and remove wastes.

• Aligned the emerging field of public health with the economic priorities of government.

1700s and early 1800s Average life expectancy was…

Hovered around 35 to 40 years

The Evolution of Public Health in the United States: 1700s

Congress established the U.S. Marine Hospital Service (MHS)

• Marked the birth of federal public health care and the direct precursor to the U.S. Public Health Services

• MHS dealt with the health problems of sick and disabled seamen

• MHS was the predecessor of the United States Public Health Services ( USPHS )

The Evolution of Public Health in the United States: 1800s

Chadwick advocated for improving living conditions in order to improve health

The Evolution of Public Health in the United States: Early 1900s

United States Public Health Service (USPHS ) was established

The Evolution of Public Health in the United States: Mid 1900s

Creation of the U.S. Department of Health, Education, and Welfare ( USDHEW )

The Evolution of Public Health in the United States: Late 1900s

Executive branch reorganization resulting in creation of the United States Department of Health and Human Services ( USDHHS )

Department of Health and Human Services ( HHS )

Stated mission: To enhance and protect the health and well-being of all Americans:

• Directly delivering a range of health and human services

• Promoting advances in public health and medical research

• Carrying out aspects of health policy

World Health Organization (WHO) and Global Health Services

_____ is the body charged with governance of health on a global scale.

Public health services are also delivered by:

• National and international nongovernmental agencies

• Community programs around the globe

The Evolution of Academic Schools of Public Health in the United States:

Early 1900s

The first U.S. school of public health opened

• Health education curriculum was distinct from medical school training.

• Initial focus was on infectious diseases.

The Evolution of Academic Schools of Public Health in the United States:

Mid 1900s

• Association of Schools of Public Health (ASPH) formed

• APHA-accredited graduate public health programs.

The Evolution of Academic Schools of Public Health in the United States:

Late 1900s [ 1974 ]

• APHA establishes the Council on Education for Public Health (CEPH)

The Evolution of Academic Schools of Public Health in the United States:

Early 2000~2010s [ 2013 ]

• ASPH becomes the Association of Schools and Programs of Public Health (ASPPH).

Communicable disease

• Also known as infectious or transmissible disease

• A disease that is passed from an infected person, who harbors an infectious agent such as bacteria or virus, to a previously noninfected person

Noncommunicable disease

• Also known as a nontransmissible disease

• Characterized by an absence of contagion or communicability

• “Noncommunicable” is not precisely accurate because diseases are transmitted between

people through social interaction

• Dominate higher-income countries

The primary metric used in the The Global Burden of Disease ( GBD ) study is….

The disability-adjusted life year (DALY)

Prevention benefits include…

• Spares people from developing preventable illnesses

• Reduces healthcare costs

• Improves productivity

• Enhances quality of life

Dramatic gains in life expectancy are based on three factors

• Accelerating economic growth

• Recognition of infectious diseases

• Improved sanitation practices

Upstream:

• Producing health by intervening to prevent the occurrence of the risk factor

(primordial prevention)

• Producing health by adopting risk-reducing behaviors (primary prevention)

Midstream:

Secondary prevention strategies (e.g. screening) operate throughout the lifetime

Downstream

Tertiary prevention is purely a _____ approach; health has already been

compromised

The Community Health Assessment ( CHA ) is a foundational tool used by public health agencies to:

• Identify community health problems and inequities.

• Engage multisectoral partners in identifying solutions.

• Monitor health status using SDOH measures.