To ensure better health, the responsibilities in public health are threefold: assessment, policy development, and assurance ¹ (i.e., ensuring that appropriate services are available and accessible to meet the needs of the population). Chapter 2 provides tools for estimating the health of a population, and Chapter 14 discusses several definitions of health and their limitations. This chapter summarizes the current health of the U.S. population in the second decade of the 21st century and discusses data sources that public health practitioners can use to better understand the health issues in their communities. Injuries are also discussed in this chapter, both as a significant source of premature mortality, and as an example of how to think systematically about public health prevention efforts. Chapters 25 and 26 outline the U.S. public health system and how communities can improve their health. Chapters 27 and 28 address the specific public health topics of preparing for emergencies and ensuring the best quality of health care. Chapter 29 considers the complex and sometimes contradictory efforts of the medical care system to provide medical care, some of which can be considered preventive. Lastly, Chapter 30 outlines the important connections among environmental/ecological health, the health of other species, and human health and highlights new, integrative approaches for enhancing the “one health” we all share.

I Definitions of Public Health

The term public health has the following two meanings:

Health status of the public (i.e., a defined population)

Organized social efforts to preserve and improve the health of a defined population

The best-known definition of public health in terms of this second meaning was written in 1920 by C.-E. A. Winslow ² and is still remarkably current:

Public health is the science and art of preventing disease, prolonging life, and promoting physical health and efficiency through organized community efforts for the sanitation of the environment, the control of community infections, the education of the individual in principles of personal hygiene, the organization of medical and nursing service for the early diagnosis and preventive treatment of disease, and the development of the social machinery which will ensure to every individual in the community a standard of living adequate for the maintenance of health.

This definition is especially significant in the following three ways:

1. It states the central emphasis of all public health work—promoting health and preventing disease.

2. It emphasizes the diverse strategies required to promote health and prevent disease, including environmental sanitation, specific disease control efforts, health education, medical care, and an adequate standard of living.

3. It clarifies that for these goals to be achieved, organized social action is required. This action is largely expressed in the policies of the federal, state, and local governments and in the activities of the agencies designed to promote and protect the health of the public.

II Health in the United States

A Major Sources of Mortality and Morbidity

All efforts to improve public health start with an assessment. Table 24-1 shows major metrics of public health in the United States. Overall metrics of mortality have been steadily improving since 1950. Life expectancy at birth has improved to 78.2 years, and overall infant mortality has declined to less than 7 per 1000 newborns.³

Table 24-1 Major Metrics and Sources of Mortality and Morbidity, United States

The three leading causes of death have changed recently. Historically, heart disease has been the number-one killer (which it remains), followed by cancer and stroke (cerebrovascular accident). As the mortality of all these diseases has decreased, mortality from chronic lower respiratory diseases has increased and is now third on the list. Mortality from Alzheimer’s dementia has also increased, surpassing that from diabetes in 2009. The three leading cancers have long been lung, breast/prostate, and colorectal cancer. The trends over time have shown a large increase in lung cancer after the widespread use of tobacco. This peak has leveled off for men (Fig. 24-1). For women, the trend came later and has yet to level off (Fig. 24-2).

Figure 24-1 Age-adjusted cancer death rates for males by cancer site, United States, 1930–2008.

(From American Cancer Society: Cancer facts and figures: 2012, Atlanta, 2012, ACS. http://www.cancer.org/acs/groups/content/@epidemiologysurveillance/documents/document/acspc-031941.pdf)

Figure 24-2 Age-adjusted cancer death rates for females by cancer site, United States, 1930–2008.

(From Anerican Cancer Society: Cancer facts and figures: 2012, Atlanta, 2012, ACS.)

Globally, developing countries are undergoing a demographic and epidemiologic transition. Demographically, the population in these countries ages; epidemiologically, infectious diseases become less important as causes of death and chronic disease and cancers more important. In keeping with this trend, the global cancer burden is rising. Cancer trends in many developed countries are similar to U.S. trends. Developing countries have a larger burden of cancers from preventable infectious causes, such as cervical cancer.⁴ Further data on global cancer statistics can be found online.⁵

Society should have an interest in reducing all mortality, but many public health officials have an appropriate and particular interest in reducing premature deaths. One way to account for the impact of mortality causes on premature death is to calculate years of potential life lost (YPLL). Figure 24-3 shows the 10 leading causes of YPLL before age 75 between 2000 and 2009. Analyzing the data in this way reverses first and second places on the mortality list; cancer is now the number-one cause of premature death because it affects more young people. Calculating the data this way also shows that chronic diseases such as chronic lower respiratory diseases and diabetes are less important in causing premature mortality. Intentional and unintentional injuries play a major role in premature death because they disproportionately affect younger people.

Figure 24-3 Causes of years of potential life lost (YPLL), United States, 2000–2009.

(From National Center for Injury Prevention and Control, Atlanta, 2010, Centers for Disease Control and Prevention. http://webappa.cdc.gov/sasweb/ncipc/ypll10.html)

B Actual Causes of Death

The previous death statistics are based on death certificates filled out by clinicians and do not account for the full causal pathway leading to death. One metric that attempts to account for this fact is actual causes of death. This metric was outlined for the first time in a landmark paper by McGinnis and Foege and last updated in 2004.⁶ This analysis showed that smoking, poor diet, and lack of physical activity were the main drivers of mortality. However, analyzing actual causes of death should not be interpreted as a reduction of all mortality on individual behavior and an exoneration of structural determinants of health. As discussed in Chapters 14, 20, and 26, poverty, food environments, and safe environments all play an important role in shaping or enabling behavior.

C Disability-adjusted Life Years

With death rates falling, many persons live with serious illness and disability for many years. To assess this burden of disease, a metric called disability-adjusted life years (DALY) has been developed. This metric captures both the length of life lost from premature death and the time spent in poor health.⁷ By this metric, the leading sources of premature death and disability were cardiovascular disease, cancer (especially breast and lung), depression, osteoarthritis, diabetes, and alcohol use. There were significant differences between genders and among ethnic groups. For example, for women, depression was the second leading cause of DALY (10 for males), whereas motor vehicle injuries and HIV-related deaths accounted for more DALY among ethnic minorities.

D Health Care Disparities

The goal of public health is not just to decrease mortality and morbidity overall but also to decrease disparities. Historically, there has long been a gap between male and female life expectancy, as well as between whites and blacks. This gap has decreased somewhat but still exists; overall, white women live the longest, and black men are most likely to die early (Fig. 24-4). In this analysis, race is likely not the causative agent but may be a correlate of proximate causes of decreased life expectancy, such as socioeconomic status and empowerment. Effective strategies to address health care disparities have been identified at the state and local level (see Chapter 26).

Figure 24-4 Life expectancy at birth, by race and gender, United States, 1980–2007.

(From Health of the United States 2010, Washington, DC, 2010, US Department of Health and Human Services. http://www.cdc.gov/nchs/data/hus/hus10.pdf)

Health care disparities occur in all age groups but are exacerbated in particular groups. Although mortality rates and infant and child mortality all have improved significantly in the past five decades, this is not the case for young persons age 15 to 24.⁸ The three leading causes of death in this age group include unintentional injuries (mainly motor vehicle crashes), homicide, and suicide (Fig. 24-5).

Figure 24-5 Mortality rates among youth ages 15 to 24 by race, 1935–2007.

(From Singh GK: Youth mortality in the United States, 1935–2007, Rockville, Md, 2010, DHHS.)

Even among young people, injury rates vary by region and ethnicity. Non-Hispanic black and American Indians/Alaska Natives have much higher mortality rates than the other races, largely because of higher rates of unintentional injuries (American Indian), homicides (non-Hispanic black), and suicide (American Indian).

See Figure 24-6 on studentconsult.com for youth mortality by causes of death and ethnicity.

Figure 24-6 Youth mortality by causes of death and ethnicity.

(From Singh GK: Youth mortality in the United States, 1935-2007, Rockville, Md, 2010, DHHS.)

Disparities in access to care, outcomes, and mortality persist, especially among poor and minority populations. The elimination of such disparities remains a public health priority and is the subject of dedicated institutes.

III Data Sources in Public Health

Public health data are used in research and in community assessment to evaluate, to plan, to foster accountability, and to spur change. To obtain and analyze health indicator data, epidemiologists rely on a variety of sources. Data for the rates used in epidemiologic studies can be discussed in terms of numerator data, which define the population experiencing events or conditions of concern, and denominator data, which define the population at risk. Statistics gathered from health, disease, birth, and death registries, as well as from other surveys, are used in the numerator. Census statistics are used in the denominator.

In clinical epidemiology, health-related data usually derive from patient examinations, clinical records, and studies of specific clinical populations. When monitoring the health of large populations, epidemiologists use existing databases as much as possible to reduce costs and accelerate results.

The increasing availability of electronic medical records and other digitized repositories constitutes an explosion of public health data. The main challenge is no longer to find data, but to find useful data in a sea of sources. Box 24-1 illustrates an example of pulling information together for assessing the burden of disease from asthma in a community.

Box 24-1 Using Data from Multiple Sources to Assess Level of Asthma Morbidity in a New York County

In assessing the burden of disease in their community, public health planners need to access data from many sources. This involves an iterative process in which planners move between primary data collection in their community to publicly available data and back to more primary data collection. The following is a description of the steps a hypothetical public health planner might take to assess the disease burden from asthma in a county in New York State. Readers should note that New York has additional state-level resources. For states with a less active (or well-funded) state health department, planners may need to do more primary data collection. Because hospitalizations for asthma are considered preventable with optimal primary care, benchmark data are available from the Agency for Healthcare Research and Quality (AHRQ). This may not be true for other community health problems.

A. Describe the asthma prevalence and mortality among adults and children in the state, and describe trend.

1. Assess the prevalence rate of adult asthma in certain subgroups (age, gender, race/ethnicity). (BRFSS)

2. Compare the county adult asthma prevalence rate with the state. (BRFSS/EBRFSS)

3. Assess the county adult asthma prevalence in population subgroups (age, gender, race/ethnicity). (BRFSS/EBRFSS)

4. Compare the county population subgroup patterns to the state subgroups for adult asthma prevalence. (BRFSS/EBRFSS)

5. Assess current asthma prevalence among children in the state. (National Asthma Surveillance—NY)

6. Compare the state childhood asthma prevalence among population subgroups. (National Asthma Surveillance—NY)

7. Perform primary data collection for county childhood asthma prevalence.

8. Compare the county childhood asthma prevalence with the state prevalence.

9. Compare the asthma mortality rate for the state and county. (Vital Records—3 years)

B. Assess health care utilization resulting from asthma.

1. Assess current rate of hospital discharge from asthma, and describe trends in different age groups (total, 0-17, 18-64, 65+; likely need to obtain from hospitals directly or from state hospital association).

2. Compare the 3-year rates for state versus county by age.

3. Compare hospitalization rate by zip code for 3 years; where are the high risk areas?

4. Assess emergency room data—1-year cross-sectional; what percentage is asthma-related? Look at age, gender, race/ethnicity, and payment source distributions.

5. Calculate the risk ratio for someone who lives in the ____ zip code being hospitalized/seen in the emergency room for asthma: ___; compared to other zip codes in the county.

6. Compare county asthma hospitalization rate to benchmark. (AHRQ)

C. Describe overall health of the county.

1. Assess median family income/per-capita income by zip code (from census).

2. Assess county health ranking. (countyhealthranking or American Community Survey).

3. Assess air quality (EPA).

4. Could also assess adult and adolescent smoking rates (BRFSS and YBRFSS).

D. Perform primary data collection.

1. Estimate sample size for sampling school asthma survey.

2. Compare prevalence rates from school asthma data of four schools (two high-risk areas, one moderate-risk area, and one low-risk area).

E. Review primary data and determine if other data sources need to be accessed.

Note: The primary data collection will likely bring up more issues that require comparison to state and county averages.

BRFSS, Behavioral Risk Factor Survey System (E, Expanded; Y, Youth); EPA, Environmental Protection Agency.

Modified from Epi Info Community Health Assessment Tutorial 2.0, 2005, Department of Health and Human Services, CDC, National Center for Public Health Informatics. ftp://ftp.cdc.gov/pub/Software/epi_info/EIHAT_WEB/EIHAT2.0.pdf

Public health planning in the United States benefits from many high-quality health-related surveys that are done regularly. With the growth of the Internet, social media, and applications that pinpoint the location of multiple people, new sources for surveillance have become available.

The most important uses of the data remain to foster accountability and to spur change. In an ideal world, everyone would use a coherent set of population health metrics to drive such change. To date, however, no coherent and consistent set is available.⁹ Health knowledge should not devolve into its converse, morbidity and mortality (Fig. 24-7).¹⁰ In keeping with theories of health and its determinants, such a consistent set of health indicators should measure not only disease burden but also health equity, social determinants of health, environmental monitoring, quality of life, and aspects of health system performance.

Figure 24-7 Knowing about health.
^aThe ongoing, systematic collection, analysis, and interpretation of health-related data with the a priori purpose of identifying unusual events of public health importance, or preventing or controlling disease or injury, followed by their dissemination for public health action. For example:
^bVital registration, cancer registries, exposure registries.
^cMedical and laboratory records, pharmacy records.
^dWeather, climate change, pollution.
^eCriminal justice information, Lexis-Nexis, census.

(From Lee LM, Thacker SB: Public health surveillance and knowing about health in the context of growing sources of health data, Am J Prev Med 41:636–640, 2011.)