PREVENTION OF CARDIOVASCULAR DISEASE

Cardiovascular diseases, including coronary heart disease (CHD) and stroke, represent two of the most important causes of morbidity and mortality in developed countries. Several risk factors increase the risk for coronary disease and stroke. These risk factors can be divided into those that are modifiable (eg, lipid disorders, hypertension, cigarette smoking) and those that are not (eg, gender, age, family history of early coronary disease). Impressive declines in age-specific mortality rates from heart disease and stroke have been achieved in all age groups in North America during the past two decades, in large part through improvement of modifiable risk factors: reductions in cigarette smoking, improvements in lipid levels, and more aggressive detection and treatment of hypertension. This section considers the role of screening for cardiovascular risk and the use of effective therapies to reduce such risk. Key recommendations for cardiovascular prevention are shown in Table 1–3.

Abdominal Aortic Aneurysm

One-time screening for abdominal aortic aneurysm (AAA) by ultrasonography in men aged 65–75 years is associated with a significant reduction in AAA-related mortality (odds ratio, 0.56 [95% CI, 0.44 to 0.72]). With long-term (7-15 years) follow-up, the reduction in AAA-related mortality is sustained, and screening appears to produce a reduction in all-cause mortality (OR = 0.94, 95% CI 0.92, 0.97). Women do not appear to benefit from screening, and most of the benefit in men appears to accrue among current or former smokers. Recent analyses suggest that screening men aged 65 years and older is highly cost-effective.

Cigarette Smoking

 

Cigarette smoking remains the most important cause of preventable morbidity and early mortality. In 2000, there were an estimated 4.8 million premature deaths in the world attributable to smoking, 2.4 million in developing countries and 2 million in industrialized countries. More than three-quarters (3.8 million) of these deaths were in men. The leading causes of death from smoking were cardiovascular diseases (1.7 million deaths), chronic obstructive pulmonary disease (COPD) (1 million deaths), and lung cancer (0.9 million deaths). Cigarettes are responsible for one in every four deaths in the United States. Fortunately, US smoking rates are declining. Currently, 20% of US adults and 21.6% of adolescents in 12th grade are smokers.

Nicotine is highly addictive, raises brain levels of dopamine, and produces withdrawal symptoms on discontinuation. Smokers die 5–8 years earlier than never-smokers. They have twice the risk of fatal heart disease, 10 times the risk of lung cancer, and several times the risk of cancers of the mouth, throat, esophagus, pancreas, kidney, bladder, and cervix; a twofold to threefold higher incidence of stroke and peptic ulcers (which heal less well than in nonsmokers); a twofold to fourfold greater risk of fractures of the hip, wrist, and vertebrae; four times the risk of invasive pneumococcal disease; and a twofold increase in cataracts.

In the United States, over 90% of cases of COPD occur among current or former smokers. Both active smoking and passive smoking are associated with deterioration of the elastic properties of the aorta (increasing the risk of aortic aneurysm) and with progression of carotid artery atherosclerosis. Smoking has also been associated with increased risks of leukemia, of colon and prostate cancers, of breast cancer among postmenopausal women who are slow acetylators of N-acetyltransferase-2 enzymes, osteoporosis, and Alzheimer disease. In cancers of the head and neck, lung, esophagus, and bladder, smoking is linked to mutations of the P53 gene, the most common genetic change in human cancer. Patients with head and neck cancer who continue to smoke during radiation therapy have lower rates of response than those who do not smoke. Olfaction and taste are impaired in smokers, and facial wrinkles are increased. Heavy smokers have a 2.5 greater risk of age-related macular degeneration.

The children of smokers have lower birth weights, are more likely to be mentally retarded, have more frequent respiratory infections and less efficient pulmonary function, have a higher incidence of chronic ear infections than children of nonsmokers, and are more likely to become smokers themselves.

In addition, exposure to environmental tobacco smoke has been shown to increase the risk of cervical cancer, lung cancer, invasive pneumococcal disease, and heart disease; to promote endothelial damage and platelet aggregation; and to increase urinary excretion of tobacco-specific lung carcinogens. The incidence of breast cancer may be increased as well. Of approximately 450,000 smoking-related deaths in the United States annually, as many as 53,000 are attributable to environmental tobacco smoke. Annual costs of smoking-related health care is approximately $96 billion per year in the United States, with another $97 billion in productivity losses.

Smoking cessation reduces the risks of death and of myocardial infarction in people with coronary artery disease; reduces the rate of death and acute myocardial infarction in patients who have undergone percutaneous coronary revascularization; lessens the risk of stroke; slows the rate of progression of carotid atherosclerosis; and is associated with improvement of COPD symptoms. On average, women smokers who quit smoking by age 35 add about 3 years to their life expectancy, and men add more than 2 years to theirs. Smoking cessation can increase life expectancy even for those who stop after the age of 65.

Although tobacco use constitutes the most serious common medical problem, it is undertreated. Almost 40% of smokers attempt to quit each year, but only 4% are successful. Persons whose clinicians advise them to quit are 1.6 times as likely to attempt quitting. Over 70% of smokers see a physician each year, but only 20% of them receive any medical quitting advice or assistance.

Factors associated with successful cessation include having a rule against smoking in the home, being older, and having greater education. Several effective interventions are available to promote smoking cessation, including counseling, pharmacotherapy, and combinations of the two. The five steps for helping smokers quit are summarized in Table 1–4.

Common elements of supportive smoking cessation treatments are reviewed in Table 1–5. A system should be implemented to identify smokers, and advice to quit should be tailored to the patient’s level of readiness to change. Pharmacotherapy to reduce cigarette consumption is ineffective in smokers who are unwilling or not ready to quit. Conversely, all patients trying to quit should be offered pharmacotherapy except those with medical contraindications, women who are pregnant or breast-feeding, and adolescents. Weight gain occurs in most patients (80%) following smoking cessation. For many, it averages 2 kg, but for others (10–15%) major weight gain—over 13 kg—may occur. Planning for the possibility of weight gain, and means of mitigating it, may help with maintenance
of cessation.

Several pharmacologic therapies have been shown to be effective in promoting cessation. Nicotine replacement therapy doubles the chance of successful quitting. The nicotine patch, gum, and lozenges are available over-thecounter, and nicotine nasal spray and inhalers by prescription. The sustained-release antidepressant drug bupropion (150–300 mg/d orally) is an effective smoking cessation agent and is associated with minimal weight gain, although seizures are a contraindication. It acts by boosting brain levels of dopamine and norepinephrine, mimicking the effect of nicotine. More recently, varenicline, a partial nicotinic acetylcholine-receptor agonist, has been shown toimprove cessation rates; however, its adverse effects, particularly its effects on mood, are not completely understood and warrant careful consideration. No single pharmacotherapy is clearly more effective than others, so patient preferences and data on adverse effects should be taken into account in selecting a treatment.

Clinicians should not show disapproval of patients who failed to stop smoking or who are not ready to make a quit attempt. Thoughtful advice that emphasizes the benefits of cessation and recognizes common barriers to success can increase motivation to quit and quit rates. An intercurrent illness such as acute bronchitis or acute myocardial infarction may motivate even the most addicted smoker to quit.

Individualized or group counseling is very cost-effective, even more so than treating hypertension. Smoking cessation counseling by telephone (“quitlines”) has proved effective, and a recent trial showed a text messaging-based intervention to be effective. An additional strategy is to recommend that any smoking take place out of doors to limit the effects of passive smoke on housemates and coworkers. This can lead to smoking reduction and quitting.

The clinician’s role in smoking cessation is summarized in Table 1–4. Public policies, including higher cigarette taxes and more restrictive public smoking laws, have also been shown to encourage cessation, as have financial incentives directed to patients.

Lipid Disorders

Higher low-density lipoprotein (LDL) cholesterol concentrations and lower high-density lipoprotein (HDL) levels are associated with an increased risk of CHD. Cholesterol lowering therapy reduces the relative risk of CHD events, with the degree of reduction proportional to the reduction in LDL cholesterol achieved. The absolute benefits of screening for—and treating—abnormal lipid levels depend on the presence and number of other cardiovascular risk factors, including hypertension, diabetes, smoking, age, and gender. If other risk factors are present, cardiovascular risk is higher and the benefits of therapy are greater. Patients with known cardiovascular disease are at higher risk and have larger benefits from reduction in LDL cholesterol.

Evidence for the effectiveness of statin-type drugs is better than for the other classes of lipid-lowering agents or dietary changes specifically for improving lipid levels. Multiple large randomized, placebo-controlled trials have demonstrated important reductions in total mortality, major coronary events, and strokes with lowering levels of LDL cholesterol by statin therapy for patients with known cardiovascular disease. Statins also reduce cardiovascular events for patients with diabetes mellitus. For patients with no previous history of cardiovascular events or diabetes, a meta-analysis showed important reductions of cardiovascular events. The JUPITER trial suggested that statins reduce coronary events relatively similarly for both men and women.

Guidelines for therapy are discussed in Chapter 28.

Hypertension

Over 43 million adults in the United States have hypertension, but 31% are unaware of their elevated blood pressure; 17% are aware but untreated; 29% are being treated but have not controlled their blood pressure (still greater than 140/90 mm Hg); and only 23% are well controlled. In every adult age group, higher values of systolic and diastolic blood pressure carry greater risks of stroke and congestive heart failure. Systolic blood pressure is a better predictor of morbid events than diastolic blood pressure. Home monitoring is better correlated with target organ damage than clinic-based values. Clinicians can apply specific blood pressure criteria, such as those of the Joint National Committee, along with consideration of the patient’s cardiovascular risk and personal values, to decide at what levels treatment should be considered in individual cases. Table 11–1 presents a classification of hypertension based on blood pressures.

Primary prevention of hypertension can be accomplished by strategies aimed at both the general population and special high-risk populations. The latter include persons with high-normal blood pressure or a family history of hypertension, blacks, and individuals with various behavioral risk factors such as physical inactivity; excessive consumption of salt, alcohol, or calories; and deficient intake of potassium. Effective interventions for primary prevention of hypertension include reduced sodium and alcohol consumption, weight loss, and regular exercise. Potassium supplementation lowers blood pressure modestly, and a diet high in fresh fruits and vegetables and low in fat, red meats, and sugar-containing beverages also reduces blood pressure. Interventions of unproven efficacy include pill supplementation of potassium, calcium, magnesium, fish oil, or fiber; macronutrient alteration; and stress management.

Improved identification and treatment of hypertension is a major cause of the recent decline in stroke deaths as well as the reduction in incidence of heart failure-related hospitalizations. Because hypertension is usually asymptomatic, screening is strongly recommended to identify patients for treatment. Despite strong recommendations in favor of screening and treatment, hypertension control remains suboptimal. An intervention that included patient education and provider education was more effective than provider education alone in achieving control of hypertension, suggesting the benefits of patient participation; another trial found that home monitoring combined with telephone-based nurse support was more effective than home monitoring alone for blood pressure control. Pharmacologic management of hypertension is discussed in Chapter 11.

Chemoprevention

 

As discussed in Chapters 10 and 24, regular use of low-dose aspirin (81–325 mg) can reduce the incidence of myocardial infarction in men. Low-dose aspirin reduces stroke but not myocardial infarction in middle-aged women. Based on its ability to prevent cardiovascular events, aspirin use appears cost-effective for men and women who are at increased cardiovascular risk, which can be defined as 10-year risk over 10%. Results from a meta-analysis suggest that aspirin may also reduce the risk of death from several common types of cancer.

Nonsteroidal anti-inflammatory drugs may reduce the incidence of colorectal adenomas and polyps but may also increase heart disease and gastrointestinal bleeding, and thus are not recommended for colon cancer prevention in average risk patients.

Antioxidant vitamin (vitamin E, vitamin C, and betacarotene) supplementation produced no significant reductions in the 5-year incidence of—or mortality from—vascular disease, cancer, or other major outcomes in high-risk individuals with coronary artery disease, other occlusive arterial disease, or diabetes mellitus. More recently, a large prospective cohort study found modestly increased risk of mortality with several common dietary supplements.