Public Health

Public health refers to those activities by which a society attempts to increase life expectancy, decrease morbidity, and help improve health-related quality of life. A distinction is sometimes made between clinical or high-risk approaches to disease treatment and prevention versus population-based strategies. Although there is some utility in distinguishing between these approaches, they should be seen as complementary because neither strategy is effective for all behaviors or all target groups. Thus, an important public health task is to identify which risk behaviors are amenable to individual-based versus population-based interventions and how to make these interventions synergistic with one another.

Application of the social and behavioral sciences to improve health and combat disease occurs at multiple levels and requires implementation of different skills both within and across levels. Genetic counseling for those at familial risk of disease, family counseling to reduce substance abuse or interfamilial violence and group counseling to help those living with HIV/AIDS are examples of interpersonal interventions at the individual level. At the organizational level, interpersonal intervention such as blood pressure screenings and smoking cessation programs, the provision of physical fitness facilities, and media communication have been used in schools, work sites, and community centers. Finally, societal-type interventions involving media and policy actions can occur at the community, state, or federal level. Seat-belt laws, public service announcements about drunk driving, and taxation of cigarettes are examples of interventions at this level.

To achieve public health objectives, it is sometimes useful to deal with intransigent problems at multiple levels. Although behavioral interventions administered at the individual level tend to produce successful weight loss in the short term, few people maintain their weight loss over the long term. In order for individual-based interventions to succeed on a population basis, such interventions should take place in a sociocultural environment that is conducive to healthful eating and exercise. Improving the availability of healthy food choices, providing economic incentives for healthy eating by selective taxation, ensuring through the schools that children and adolescents get adequate exercise, enhancing accessibility of physical activity for the general public by providing bicycle paths and highway lanes, and initiating mass media campaigns supporting a healthy lifestyle could be useful for maintaining weight loss.

The relatively recent successes in tobacco control in the United States provide a heartening example of how multilevel approaches to a major public health problem can lead to a decline in disease. In this case the improvements have occurred in coronary heart disease (CHD), some cancers including lung cancer, and respiratory diseases. At the interpersonal level, smoking cessation interventions, sometimes in conjunction with pharmacologic treatment, have been effective. At the organizational level, smoking cessation support groups, school campaigns against smoking, restrictions on smoking in restaurants and work sties, and reductions in health insurance premiums for nonsmokers have been instituted. Finally, at the societal level, laws against juvenile smoking, taxation of cigarettes, governmental restrictions on tobacco advertising, and government-sponsored antismoking campaigns have all been implemented. These measures have led to a marked reduction in cigarette smoking and a concomitant improvement in the nation’s health. Unfortunately, the export of tobacco products to other countries remains a threat to improvements in global public health.

An important cornerstone of public health is prevention. Primary prevention refers to measures taken to reduce the incidence of disease. In the case of CHD, for example, people may be encouraged to quit smoking, decrease intake of dietary fat, and increase physical activity before diseases become evident. In contrast, secondary prevention involves reducing the prevalence of disease by shortening its duration and limiting adverse physiological and psychological effects. Screening programs are examples of secondary prevention strategies. Breast cancer and prostate cancer mortality are decreased by early detection of cancers when they are still treatable. Still another form of prevention is tertiary prevention. This involves reducing the complications associated with chronic diseases and minimizing disability and suffering. Medication adherence training in HIV/AIDS patients is a form of tertiary prevention.

The first half of the 20th century witnessed an unprecedented increase in longevity primarily in economically advanced countries. This decrease in mortality rate was largely due to a decline in infectious diseases related to vaccination, decreased exposure to infection because of improved hygiene, improved nutrition, and the development of antibiotics to cope with bacterial infections. As infectious diseases declined as the leading cause of mortality in economically advanced countries, they were eclipsed by chronic diseases. By the middle of the 20th century, CHD, cancer and stroke accounted for more than 60% of the death rate in the United States.

As scientists attempted to find specific causal agents in the pathogenesis of cancer and CHD throughout most of the 20th century, they became increasingly frustrated. Unable to find single causes of diseases, attention shifted to the role of environment and host in the pathogenesis of chronic diseases. Whereas single cause-and-effect models proved successful in studying the genesis of infectious diseases, an understanding of the basis of chronic diseases turned to probabilistic models based on the presence of risk factors. The identification of risk factors makes prediction of chronic diseases more likely, but individual risk factors cannot be identified as necessary and sufficient causes for many diseases. In this respect, interactions among agent, host, and the environment have now taken center stage.

At the beginning of the risk-factor revolution, it was widely believed that the causes of chronic diseases such as CHD could be explained in terms of a few biological (e.g., high cholesterol, high blood pressure) and lifestyle (e.g., smoking) risk factors. This turned out not to be the case. Other variables contributing to CHD turned out to include physical inactivity, excess consumption of alcohol, and obesity. Still other factors under investigation include individual difference variables such as depression and hostility and sociocultural variables including low socioeconomic status, ethnic minority status, lack of social support, and occupational stress.

At the turn of the 21st century the major causes of death in the United States included (1) heart disease (2) cancer (3) stroke (4) unintentional injuries (5) chronic obstructive pulmonary disorder (6) pneumonia and influenza (7) diabetes (8) suicide (9) liver disease (10) HIV/AIDS and (11) homicide. Behavioral, psychosocial, and sociocultural factors associated with lifestyle contribute to virtually all of these causes of mortality. Even in the case of an infectious disease such as pneumonia, risk factors can be related to disruptions of natural pulmonary host mechanisms related to lifestyle factors such as smoking and alcohol abuse. Similarly, infection from HIV is primarily spread through high-risk sexual practices and the sharing of contaminated drug paraphernalia.

In conclusion, public health efforts to eradicate infectious diseases led to an unprecedented increase in longevity in economically developed and even many less developed countries during the first half of the 20th century. Similarly, improvements in healthy lifestyle led to decreases in morbidity and increases in longevity in these countries during the second half of the 20th century. In contrast, the dissolution of the Soviet Union toward the end of the 20th century led to a precipitous drop of life expectancy in Russia and several other Eastern European countries. This has been related to increases in poverty, social disintegration, and environmental pollution superimposed on high rates of alcoholism and tobacco use. At the same time, the HIV/AIDS pandemic in sub-Saharan Africa has led to an even steeper decline in life expectancy. The growing spread of HIV/AIDS across the Asian continent is ominous. Widespread social disorganization and the growing disparity in income within and between nations also pose a global threat to public health. Because public health is a global matter that is closely tied to international policies, hope for future improvements in public health will largely depend on global improvements in public policy.