What is preventive medicine?

Science and Profession

Modern preventive medicine is considered to exist at three levels within the health-care community. The initial level, primary prevention, aims to maintain health by removing the causes of, or protecting the community or individual from, agents of disease and injury. These activities are no longer limited to the prevention of infection; they now include improvement in the environment and behavioral changes to reduce risk factors that contribute to chronic disease and injury. An example of primary prevention is immunization programs for children. To reduce the risk of heart attack, one should refrain from smoking, be active, and reduce fat intake—all wise primary prevention actions. Halting the loss of atmospheric ozone, reducing air and water pollution, and developing environmentally friendly technologies form another class of prevention actions.

Secondary prevention seeks to detect and correct adverse health conditions before they manifest as disease by reversing, halting, or retarding the disease process. One frequently used secondary prevention technique is health screening. Examples include screening services for hypertension (high blood pressure), diabetes, prostate cancer, and glaucoma. In industry, routine hearing tests are used as a tool to prevent noise-induced hearing loss among the workforce. Once a potential health problem is identified, clinical preventive medicine techniques can be instituted to reverse the condition or prevent further progression.

Tertiary prevention seeks to minimize the adverse effects of disease and disability. Coronary bypass surgery, vocational rehabilitation, and treatment of an incapacitating mental illness are examples.

Specialists in the field of preventive medicine typically focus their efforts within the paradigms of primary and secondary prevention. In epidemiological terms, primary prevention results in a reduction of the incidence of a disease (the new cases occurring over time). Secondary prevention, on the other hand, results in a reduction of the prevalence of a disease (the number of people suffering from a particular illness at a given point in time).

Most physicians provide some degree of preventive medicine services. Pediatricians are practicing preventive medicine when they conduct “well-baby evaluations” and ensure that immunizations are current. Family medicine specialists are providing such services when they perform Pap testing or order mammograms. When the cessation of smoking is discussed and internists prescribe nicotine-patch regimens, that too is preventive medicine.

In the United States, physicians who specialize in preventive medicine are certified by the American Board of Preventive Medicine, which recognizes three subspecialties: public health and general preventive medicine, occupational medicine, and aerospace medicine. Some general preventive medicine specialists use epidemiological methods to design and develop prevention programs, which may feature a single intervention or may include a multitude or matrix of screening technologies and interventions. Others provide services in a clinical setting by ordering a history and physical examination, which may include age- and gender-specific screening tests. The general preventive medicine specialist then can counsel the patient on lifestyle alterations recommended to preserve or improve health.

Practicing in industry or private clinic settings, specialists in occupational medicine are concerned about preventing injury and illness as a result of the physical, biological, and chemical hazards that are present in the workplace. Should workers be injured or become ill as a result of their employment, the occupational medicine physician manages their treatment, rehabilitation, and return to work.

Specialists in aerospace medicine limit their practice to those involved in the aeronautical and space transportation fields, including flight crews, support personnel, and passengers. The major task of these physicians is to protect this population group from the adverse environmental conditions of flight, including pressure changes, reduced availability of oxygen, thermal stressors, accelerative forces, and psychosocial factors that might compromise performance.

Diagnostic and Treatment Techniques

An example of the application of preventive medicine is a comparison of the leading causes of death in the United States in 1900 with those in 2000. During the intervening time, the main causes of death underwent a major shift, from infectious diseases to chronic diseases that often reflect individual lifestyles, such as cancer and heart disease. Preventive medicine has proven itself effective in altering both the causes of death and the age at which death occurs. In addition, there was a significant increase in the life expectancy of the population during the same century. Preventive medicine now focuses on reducing morbidity and mortality from chronic diseases and accidents, particularly those in which an individual’s lifestyle increases the risk for illness and death.

Disease prevention and health promotion are the two pillars supporting the discipline of preventive medicine. Beginning in 1987, a consortium was convened to begin to address a preventive medicine strategy to improve the health of Americans. The Institute of Medicine of the National Academy of Sciences worked with the US Public Health Service and numerous other organizations to formulate health objective goals to be attained by the beginning of the twenty-first century. Once goals and objectives were established, the next task was to devise methods, technologies, and strategies to achieve the objectives by the year 2000. The resulting report was titled Healthy People 2000: National Health Promotion and Disease Prevention Objectives (1991).

The implementation of what was then known about disease prevention and health promotion was the central challenge. Good health is the result of reducing needless disease, injury, and suffering, resulting in an improved quality of life. A strategy of the Healthy People 2000 initiative was to combine scientific knowledge, professional skills, community support, individual commitment, and the public will to achieve good health. This plan required reducing premature death, preventing disability, preserving the physical environment, and enabling Americans to develop healthy lifestyles. Three broad goals were detailed in the report: first, to increase the healthy life span for Americans; second, to reduce health disparity among Americans; and third, to achieve access to preventive services for all Americans. A number of examples of the types of programs required to attain these goals were provided.

Tobacco use is the most important single preventable cause of death in the United States, accounting for more than 480,000 deaths annually, according to the Centers for Disease Control and Prevention (CDC). This loss of life is the equivalent of crashing two commercial jumbo jet airliners filled with passengers every day for a year. Smoking is a major risk factor for heart and lung disease; cancer of many organs, including the lungs, pancreas, and bladder; and stomach ulcers. Passive or environmental tobacco smoke is a recognized cause of cancer for exposed nonsmokers, and children in smoke-filled homes experience more ear infections. Tobacco use during pregnancy increases the risk of prematurity and low birth weight.

More than three million nonfatal work-related injuries occur per year in the US private sector, according to the Bureau of Labor Statistics (BLS), while the number of work-related deaths tops four thousand across all sectors. The occupations with the highest injury rates include construction, manufacturing, mining, nursing and residential care, police and fire protection, and transportation. The prevention of occupational disease and injury requires engineering controls, improved work practices, use of physical protective equipment, and monitoring of the work environment to identify emerging chemical and physical hazards.

In the United States in 2013, nearly 585,000 people died from cancer. Nearly one in three Americans will experience some form of this disease during their lifetimes. Research has helped identify many risk factors related to cancer causation, including tobacco use, low fiber intake, excess fat intake, sunburn, alcohol use, and exposure to chemical carcinogens. Information, education, and early detection all play important roles in reducing both the incidence and the prevalence of cancer. Pap smears, prostate examinations, mammograms, and oral examinations are secondary prevention procedures that allow for early diagnosis and treatment. Such screening procedures, coupled with education and lifestyle changes, have the potential to reduce cancer rates significantly.

The follow-up to Healthy People 2000 was Healthy People 2010, which, like its predecessors, was developed through a broad consultation process, built on scientific knowledge and designed to measure programs over time. The objectives of this initiative were published in the report Healthy People 2010: Understanding and Improving Health (2000). The two primary goals were to help individuals of all ages increase life expectancy and improve their quality of life and to eliminate health disparities among different segments of the population. The healthy life expectancy at birth increased slightly from 2000–2001 to 2006–7, from about seventy-seven years of age to about seventy-eight among the overall population. There were no significant changes in health disparity across race and ethnicity in 70 percent of the objective areas.

Healthy People 2020 was launched in December 2010 with an agenda similar to those of the previous Healthy People initiatives, plus several new areas of interest, including adolescent health; lesbian, gay, bisexual, and transgender health; and sleep health. The focus of Healthy People 2020 is on enabling individual health by improving the health of communities.

Achieving the many objectives of the Healthy People initiatives requires the dedicated commitment of preventive medicine specialists and the broader medical community. Enhanced effectiveness and efficiency of clinical preventive services, screening procedures, immunizations, consultation, and counseling can be achieved only through close relationships between the physician and both the community and the individual. To assess whether the goals and objectives for the prevention of disease and health promotion are realistic, it would be helpful to review a success in the application of preventive medicine. Many of the objectives for Healthy People 2010 were not met, but pesticide exposure, for example, was one area that showed marked improvement: doctor's office visits for pesticide-related issues declined from more than twenty-three thousand in 1998 to less than fifteen thousand in 2008, though this still fell short of the 2010 target of less than twelve thousand visits. Another area in which preventative medicine seemed to be effective was the reduction of adolescent pregnancies, specifically among the black population. In 1996, the rate of pregnancy per one thousand girls between the ages of fifteen and seventeen was about 130; by 2005, the rate was less than 80.

Coronary artery disease and its resultant heart attacks are preventable. A large national clinical trial of preventive medicine procedures known as MRFIT (multiple risk factor intervention trial) demonstrated not only the value of risk-factor reduction in preventing disease but also that the impact of established disease could be reversed. Those in the MRFIT population who had established coronary artery disease at the start of the study had 55 percent fewer fatalities than did the control group when both were followed over seven years.

Preventive medicine interventions are not only cost-effective but relatively inexpensive as well. For example, coronary artery bypass surgery or a heart transplant costs many times more than preventive medicine rehabilitation and lifestyle-modification programs. The same advantages also accrue for the prevention of strokes. Reducing salt intake, controlling high blood pressure, correcting obesity, performing regular exercise, and quitting smoking all reduce the risk of stroke. The evidence clearly shows that preventive medicine reduces the death rate from heart attack and stroke and enhances quality of life.

Clinical preventive services have been designed based on the best available scientific evidence to promote the health of the individual while remaining practical and cost-effective. The US Preventive Services Task Force's Guide to Clinical Preventive Services, first published in 1989 and updated several times since then, was a major milestone on the road to reducing premature death and disability. It has been well established that the majority of deaths among Americans under the age of sixty-five are preventable. The guide was the culmination of more than four years of literature review, debate, and synthesis and provides a listing of the clinical preventive services that clinicians should provide their patients. More than one hundred interventions are proposed to prevent sixty different illnesses and medical conditions. The guide is intended to be used by preventive medical specialists and other primary care clinicians. Its recommendations are based on a standardized review of current scientific evidence and include a summary of published clinical research regarding the clinical effectiveness of each preventive service.

Although there are sound clinical reasons for emphasizing prevention in medicine, studies have repeatedly demonstrated that physicians often fail to provide these services. Busy clinicians frequently have inadequate time with the patient to recommend or deliver a range of preventive services. Furthermore, until the publication of the Guide to Clinical Preventive Services, considerable controversy had existed within the medical community as to which services should be offered and how often. In the past, there was skepticism regarding the value of certain preventive interventions and their ability to reduce morbidity or mortality significantly. One result of this review process has been the clear evidence that reducing the incidence and severity of the leading causes of disease and disability is dependent on the personal health practices of individuals.

The periodic health examination was once frequently referred to as an annual examination. The Guide to Clinical Preventive Services tailors this examination to the individual needs of the patient and considers factors such as age, gender, and risk. Consequently, a uniform health examination is not recommended. The examination for those between forty and sixty-four years of age is scheduled on a one- to three-year basis, with the more frequent examinations scheduled for those in high-risk groups. Although the examination is not comprehensive, it is focused on identifying the leading causes of illness and disability among people in this age-group. During the physical examination, particular attention would be paid to the skin of those individuals at high risk for excessive exposure to sunlight or with a family or personal history of skin cancer. A complete oral cavity examination would be appropriate for individuals using tobacco or consuming excessive amounts of alcohol. Counseling would be provided on such items as diet and exercise, substance abuse, sexual practices, and injury prevention.

According to the CDC, approximately 29.1 million persons in the United States suffer from diabetes, 8.1 million of whom are undiagnosed. Diabetes was the seventh leading cause of death in the United States in 2013, accounting for more than 75,000 deaths. In addition, it is the leading cause of kidney failure, blindness, and amputations. The detection of diabetes in asymptomatic persons provides an opportunity to prevent or delay the progress of the disease and its complications.

The Guide to Clinical Preventive Services recommends an oral glucose tolerance test for all pregnant women between the twenty-fourth and twenty-eighth weeks of their pregnancy. Routine screening for diabetes in asymptomatic nonpregnant adults, using blood or urine tests, is not recommended. Periodic fasting blood-sugar measurements may be appropriate in persons at high risk for diabetes mellitus, such as the markedly obese, persons with a family history of diabetes, or women with a history of diabetes during pregnancy.

Perspective and Prospects

In the mid-nineteenth century, English physician John Snow provided one of the best examples of preventive medicine by applying what could be called observational epidemiology. During a rather severe cholera
epidemic in London, Snow observed that the pattern of disease that appeared to be dependent on the source of the water provided to each neighborhood. Recognizing that there was a high incidence of cholera in the Broad Street area, he was able to determine that most of the disease was associated with those families depending on the Broad Street pump for their drinking water. It has been said that he simply removed the handle on the pump and was able to control the epidemic in that area. His discovery occurred before there was a clear understanding of the relationship between bacteria or germs and infectious disease.

Another historic example of the application of preventive medicine was the control of smallpox. In the late eighteenth century, physician and scientist Edward Jenner observed that the milkmaids in the English countryside were not scarred by the scourge of smallpox. On further examination, he determined that these young women had years earlier been infected with cowpox and thus had been spared the more serious smallpox infection. Jenner advocated intentional infection with the cowpox in order to essentially vaccinate against smallpox. Years later, using this preventive medicine application, the World Health Organization (WHO) was able to eradicate smallpox worldwide. The world's last natural case of smallpox was reported in October 1977, marking the first time that a major human disease had been eradicated.

Neither the control of cholera in London by Snow nor the eradication of smallpox resulted from medical or surgical treatment of a disease. These results were obtained because of the application of the principles of preventive medicine and public health.

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