Prevention and the Family Physician

Prevention is central to family medicine for several reasons. A key mission of family medicine is preserving health and maximizing function of patients throughout their lives. The most common causes of morbidity and mortality are preventable chronic diseases. Prevention is important across the life span and requires repeated and evolving messaging over time. Family physicians care for patients within a family and community context that is critical to linking preventive services in the clinic with community resources. Much of prevention involves supporting patients in making healthy lifestyle changes, and family medicine has a strong foundation of behavioral medicine.

Evidence-Based Prevention

Preventive Services Task Force and Evidence-Based Prevention

The U.S. Preventive Services Task Force (USPSTF) is an independent panel of 16 private-sector experts in primary care, clinical prevention, and epidemiologic methodology (Guirguis-Blake, 2007). The USPSTF addresses a broad array of prevention topics important to primary care practice, including cancer prevention. Their recommendations address primary and secondary preventive services performed in primary care settings or recognized in primary care settings and referred to specialists. The 16 experts come from the clinical fields of family medicine, general internal medicine, pediatrics, obstetrics and gynecology, preventive medicine, behavioral medicine, and nursing. The USPSTF releases recommendations on a variety of topics relevant to family medicine that address preventive services for children, adolescents, and adults, including pregnant women.

The purpose of the USPSTF is to provide evidence-based recommendations for the provision of preventive services to apparently healthy individuals in the primary care setting. Primary and secondary preventive services addressed by the USPSTF include screening, counseling, and preventive medications. The methodology of the USPSTF is rigorous and transparent and involves the following steps:

1. Creation of an analytic framework and key questions to determine the scope of the literature review.

2. Systematic review of all relevant literature answering the key questions.

3. Quality-rating bodies of literature supporting each key question.

4. Quantification of the magnitude of benefits and harms.

5. Balancing the net benefits and harms of a specific preventive service.

The recommendation is then linked to a letter grade that reflects the magnitude of net benefit (i.e., balance of benefits and harms) and the strength of the evidence supporting the provision of a specific preventive service (see Evidence-Based Summary).

Using screening for osteoporosis as an example, the task force created a set of key questions beginning with an overarching question: Does osteoporosis screening result in decreased mortality or disability from osteoporosis? Because no evidence directly answered this question, a chain of intermediate key questions was systematically searched. What is the accuracy of screening tests (e.g., dual-energy x-ray absorptiometry [DEXA] scans)? What is the effectiveness of treatment of these screen-detected cases in preventing osteoporosis-related fractures, fracture-specific mortality, or overall mortality? What harms are caused by screening for and treatment of osteoporosis (Figure 6-1)? For USPSTF to recommend screening, each link in the chain of evidence must be supported by evidence, and there must be fair- or good-quality evidence that the benefits outweigh the harms. Any break in the chain of evidence (e.g., single key question for which there is insufficient evidence) results in a conclusion of insufficient evidence for that preventive service.

Figure 6-1 U.S. Preventive Services Task Force (USPSTF) framework for osteoporosis screening. Key questions addressed include the following: (1) Does screening using risk factor assessment or bone density testing reduce fractures? (2) Does risk factor assessment accurately identify women who may benefit from bone density testing? (3) Do bone density measurements accurately identify women who may benefit from treatment? (4) What are the harms of screening? (5) Does treatment reduce the risk of fractures in women identified by screening? (6) What are the harms of treatment?

Expressing the Burden of Disease

Risk Factors

A risk factor is a condition that is associated with an increased likelihood of a disease. For example, obesity is a risk factor for diabetes; obesity makes it more likely that a person will develop diabetes in his or her lifetime compared with someone who is not obese. Some risk factors are causal; the risk factor causes the disease. For example, smoking is a risk factor for and a proven cause of lung cancer; a smoker is many times more likely than a nonsmoker to develop lung cancer in his or her lifetime. Other risk factors are associations; people living at northern latitudes are more likely to have multiple sclerosis (i.e., there is no known causal relationship; it is simply an association). Risk factors for having a heart attack include gender, age, hypertension, smoking, and high cholesterol levels; other risk factors include sedentary lifestyle, obesity, and diabetes. Some risk factors are modifiable (i.e., can be changed), such as smoking, level of physical activity, and cholesterol levels, and others are nonmodifiable, such as age, gender, family history, and race. Some risk factors are behavioral risk factors, such as alcohol use, physical activity, and diet, and some type of change in behavior is required to modify these risk factors. Modifiable behavioral risk factors are significant contributors to most of the leading causes of death in the United States (Table 6-2). Preventive services strive to identify and change modifiable risk factors to prevent or delay disease.

Table 6-2 The 15 Leading Causes of Death—United States, 2006

When considering prevention programs, it is often cost-effective to target populations who have a higher risk of disease rather than to offer the service to the general population, in whom the risk factor or disease may be uncommon overall. For example, some sexually transmitted infections are rare in the general population but are more prevalent among certain groups of people. In some areas of the United States, gonorrhea has a prevalence of zero, whereas other areas have concentrated populations with gonorrhea. If community clinicians were asked to design a program to prevent gonorrhea, they might selectively screen those with risk factors or those living in communities with a documented high prevalence of gonorrhea. A key concept to consider is that even with a high sensitivity and specificity, screening for a risk factor or disease that is rare will result in a low positive predictive value. In other words, the yield of screening will be low, and false positives may outnumber true positives. It is therefore important to consider the burden of a risk factor or disease in a given population before deciding whether screening for that condition is worthwhile.

Cancer

Almost one in every four deaths in the United States is caused by cancer, making it the second leading cause of death. It is estimated that approximately 1500 Americans die of cancer each day; a total of 562,340 cancer deaths were expected in 2009 (National Cancer Institute [SEER], 2009). The top causes of cancer-related deaths are presented in Table 6-3. Cancer has a significant impact on individuals, their families, and society as a whole. In 2001, there were an estimated 9.8 million people alive in United States who had received the diagnosis of cancer—some still had evidence of cancer, some were in remission, and the remainder were cancer free. In 2009, an estimated 1,479,350 new cases of cancer were diagnosed. In the United States the lifetime risk of a cancer diagnosis is one in two for men and one in three for women (ACS, 2009). The National Institutes of Health (NIH) estimate that the direct and indirect overall cost of cancer in 2008 was $228 billion when total health expenditures and loss of productivity from morbidity and premature death were included.

Table 6-3 Age-Adjusted U.S. Death Rates and Trends for the Top 15 Cancer Sites^a

Heart and Vascular Disease

Cardiovascular disease is a major public health burden and the leading cause of death in the United States; it is the underlying or contributing cause in approximately 60% of deaths (Wolff et al., 2009). Effective screening tests and early preventive interventions are available for early asymptomatic states and modifiable risk factors (Figure 6-2). An assessment of cardiovascular risk using validated prediction tools is an important first step in preventing cardiovascular events. The most studied tools are based on Framingham data and are available online∗ and can be incorporated into electronic medical record systems.

Figure 6-2 Risk factors for cardiovascular disease.

(From the National Heat, Blood, and Lung Institute. http://hin.nhlbi.nih.gov/atpiii/calculator.asp?usertype=prof.)

Hypertension

Burden of Disease

Hypertension (HTN) is the most common cardiovascular disease and the most common reason patients visit family physicians (AAFP, 2002; AHA, 2005). Approximately 30% of adult Americans have hypertension; 7% of adults with HTN have never been told by their physician that they have high blood pressure (BP). Age is an important risk factor for hypertension: 7% of adults 18 to 39 years old have hypertension, versus 67% of adults age 60 and older (Ostchega et al., 2008).

The risk of death from coronary artery disease and stroke (cerebrovascular accident, CVA) is doubled with every 20–mm Hg systolic or 10–mm Hg diastolic increase in BP (Table 6-4). Elevated BP is also associated with heart failure and renal disease (JNC-7, 2004). Treatment and control of hypertension are less than ideal; 68% of hypertensive adults are treated with BP medications, and of those treated, 64% had their BP lowered to recommended levels (Ostchega et al., 2008).

Table 6-4 Adult Blood Pressure Classification System (JNC-7)

Accuracy of Screening Tests

Office-based BP measurements are typically done with a sphygmomanometer. The accuracy depends on the examiner, patient factors, and the instrument used. Because of the resulting variability, two BP measurements at separate visits are necessary for diagnosis. Properly performed measurements are highly correlated with arterial BP and predict cardiac risk. Ambulatory monitoring may be more accurate and a better predictor of cardiac risk than office BP measurement, but it is subject to the same errors. A significant advantage of ambulatory monitoring is that it may identify patients with “white coat hypertension” (Sheridan et al., 2003).

Effectiveness of Early Detection and Intervention

No studies have examined the direct effect of screening on clinical outcomes; however, treating a patient for hypertension detected through screening appears to provide morbidity and mortality benefits. The benefits of screening and treatment depend on the degree of BP elevation and the presence of other cardiovascular risk factors, such as age, gender, lipid disorders, and diabetes. Potential harms from screening include labeling and exposure to the side effects of antihypertensive treatment.

Recommendation

The USPSTF (2007) recommends that clinicians screen all adults age18 and older for high blood pressure. AHA and AAFP make similar recommendations.

Coronary Heart Disease and Cerebrovascular Disease

Burden of Disease

The epidemiology of cerebrovascular disease events is different for men and women. Men have a higher risk for coronary heart disease (CHD) and tend to have these events at a younger age than women. Women are more likely to die as a result of a myocardial infarction (MI); 38% of women die within 1 year of their first MI, versus 25% of men (Wolff et al., 2009).

Cerebrovascular disease is the third leading cause of death in the United States and approximately 500,000 people annually experience a first stroke (CVA). The mortality rate for cerebrovascular disease has declined by almost 70% since 1950, primarily because of reduced cigarette smoking and improved control of HTN. According to the Framingham data, the 10-year risk for initial ischemic stroke at age 55 years is 1.8% for women and 2.4% for men; at age 65 the risk increases to 3.9% for women and 5.8% for men (Wolff et al., 2009).

Accuracy of Screening Tests

Several screening mechanisms exist for CHD: electrocardiogram (ECG), exercise testing, and electron beam computed tomography (EBCT) for coronary calcium. The sensitivity of resting ECG abnormalities for CHD is low. The sensitivity of an exercise test ranges from 10% to 70% and the predictive value from 2.2% to 24%. False-positive results are more likely for young persons and women (Pignone et al., 2003). Evidence is limited on the use of nontraditional risk factors in CHD assessment, including ankle-brachial index (ABI), leukocyte count, fasting glucose level, periodontal disease, carotid intimal medial thickening, EBCT, homocysteine level, lipoprotein(a) level, and high-sensitivity C-reactive protein (hs-CRP) level. Screening for cerebrovascular disease with an ultrasound of the carotid artery to detect significant stenosis has a reported sensitivity of 86% to 90% and specificity of 87% to 94% (Wolff, 2007).

Effectiveness of Early Detection and Intervention

Although ECG and exercise stress tests can detect disease, the sensitivity and specificity of these tests limits their use in evaluating asymptomatic persons. False-positive results lead to invasive testing, and false-negative results lead to inappropriate reassurance. It is unclear that these assessments provide information beyond risk scoring, even for higher-risk persons. Although hs-CRP and ABI may reclassify some individuals into a higher or lower CHD risk category, evidence is lacking regarding the effect of screening or assessment with these or other modalities on outcomes (USPSTF, 2009).

Hormone replacement therapy does not prevent CHD in postmenopausal women (Anderson et al., 2004; Rossouw et al., 2002), and evidence does not support a benefit from vitamin supplements (Lee et al., 2005). There is good evidence that screening for CAS with an ultrasound leads to important harms, including strokes from confirmatory tests or surgery. For men at increased risk for CHD, aspirin prophylaxis decreases the rate of CHD events; and for women at increased risk of strokes, aspirin decreases the rate of strokes (Berger et al., 2006; USPSTF, 2009). The ideal dose is uncertain, but low doses (75 mg) are as effective as high doses (325 mg). Smoking cessation, BP and lipid control, a healthy diet, and exercise have also been shown to be beneficial in preventing cerebrovascular disease events.

Recommendation

The USPSTF recommends against using ECG, exercise testing, or CT scanning to screen low-risk adults for CHD. Evidence is insufficient to recommend these techniques even for adults at increased risk (USPSTF, 2004). AAFP does not recommend routine ECG in asymptomatic children or adults as part of a periodic health examination (Pignone et al., 2003). USPSTF concluded that the evidence is insufficient for the use of nontraditional risk factors to screen asymptomatic men and women. They recommend against screening for asymptomatic CAS in the general adult population. USPSTF recommends the use of aspirin for men age 45 to 79 years and women age 55 to 79 when the potential benefit from a reduction in MIs or strokes, respectively, outweighs the potential harm from an increase in gastrointestinal hemorrhage (Table 6-5). It is important to discuss both the benefits and the harms with patients. Aspirin in younger men and women is not recommended because they are likely to experience more harm than benefit. There is no evidence to use aspirin for cardiovascular disease prevention in average-risk men and women 80 years or older (USPSTF, 2009).

Table 6-5 10-Year Risk Levels^∗ for Coronary Heart Disease (CHD, Men) and Stroke (Women)

Substance Abuse and Mental Health

Tobacco

Burden of Disease

Tobacco use, particularly cigarette smoking, is the leading cause of preventable death in the United States, and it results in approximately 443,000 premature deaths annually (CDC, 2008a). Among adults, approximately 41% of the smoking-attributable deaths are caused by cancer, 33% by cardiovascular disease, and 26% by respiratory disease (CDC, 2008a). Smoking during pregnancy results in almost 800 (n = 776) fetal deaths annually. An estimated 49,400 deaths annually from lung cancer and cardiovascular causes are attributable to second-hand smoke exposure (CDC, 2008a). Despite the known health effects, in 2007, an estimated 19.8% of U.S. adults continued to smoke (CDC, 2008b). The prevalence of smoking is higher among certain subgroups, including Native Americans and Native Alaskans, those with a lower level of education, adults age 25 to 44, and people living below the poverty level (CDC, 2008b).

Screening and Identification of Risk Group

Clinics that implement screening systems designed to identify and document a patient’s tobacco use status increase the rate at which clinicians intervene with their patients who smoke. Including tobacco use as a “vital sign” increases the probability that tobacco use is routinely assessed and addressed. However, there is limited evidence that a screening system has a substantial impact on tobacco cessation rates (Fiore et al., 2008).

Effectiveness of Counseling Intervention

The optimal duration and frequency of tobacco counseling interventions is unknown, but good evidence indicates that even brief counseling interventions (<3 minutes) increase tobacco abstinence rates. Increasing the intensity of the counseling increases its efficacy (Fiore et al., 2008). The “5As” behavioral counseling framework provides a useful strategy for engaging patients in smoking cessation discussions (see later discussion).Providing problem-solving guidance and social support within and outside treatment is particularly important. Patients who are unwilling to try to quit should receive an intervention designed to motivate them to quit.

Several pharmacotherapies are safe and effective in helping adults to quit smoking. Nicotine replacement therapy—nicotine gum, transdermal patches, nicotine nasal spray, and nicotine inhalers—and sustained-release bupropion and varenicline are among the medications shown to be effective in increasing abstinence rates. There is limited evidence regarding the safety or efficacy of pharmacotherapy during pregnancy (Fiore et al., 2008).

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