CHAPTER 4 Introduction to Preventive medicine control their bladder and bowels. Items in the IADL scale may accelerate the development of atherosclerosis, and it include shopping, housekeeping, handling finances, and may lead to increased myocardial oxygen demand, precipi taking responsibility in administering medications. Other tating infarction earlier than it otherwise might have occurred scales are used for particular diseases, such as the Karnofsky and making recovery more difficult. In some cultures, coro index for cancer patients, and the Barthel index for stroke nary artery disease is all but unknown, despite considerable patients. genetic overlap with cultures in which it is hyperendemic, hat genot of many factors influe ing the development of atherosclerosis. I. NATURAL HISTORY OF DISEASE After a myocardial infarction occurs, some patients di some recover completely, and others recover but have serious The natural history of disease can be seen as having three sequelae that limit their function. Treatment may improve stages: the predisease stage, the latent(asymptomatic)disease the outcome so that death or serious sequelae are avoided tage, and the symptomatic disease stage. Before a disease Intensive changes in diet, exercise, and behavior(e.g,cessa- tion of smoking) may stop the progression of atheromas or disease stage-the individual can be seen as possessing even partially reverse them arious factors that promote or resist disease These factors include genetic makeup, demographic characteristics(espe cially age), environmental exposures, nutritional history, IV, LEVELS OF PREVENTION social environment, immunologic capability, and behavioral patterns. A useful concept of prevention that was developed or at least bularized in the classic account by Leavell and Clarkhas diseases)or quickly (as with most infectious diseases). If the all the activities of clinicians and other health professional disease-producing process is underway, but no symptoms of have the goal of prevention. There are three levels of preven- disease have become apparent, the disease is said to be in the tion(Table 14-1). The factor to be prevented depends on the latent(hidden)stage. If the underlying disease is detectable stage of health or disease in the individual receiving preven by a reasonably safe and cost-effective means during this tive care tage, screening may be feasible. In this sense, the latent stage Primary prevention keeps the disease process from may represent a window of opportunity during which becoming established by eliminating causes of disease or by detection followed by treatment provides a better chance of increasing resistance to disease(see Chapter 15). Secondary ure or at least effective treatment, to prevent or forestall prevention interrupts the disease process before it becomes mptomatic disease. For some diseases, such as pancreatic symptomatic( Chapter 16). Tertiary prevention limits the cancer, there is no window of opportunity because safe and physical and social consequences of symptomatic disease effective screening methods are unavailable. For other dis (Chapter 17). Which prevention level is applicable al eases, such as rapidly progressive conditions, the window of depends on which disease is the focus or what conditions are opportunity may be too short to be useful for screening considered diseases. For example, controlling cholesterol programs. Screening programs are detailed in Chapter 16 levels in an otherwise healthy person can be primary prever (see Table 16-2 for screening program criteria tion for coronary artery disease(e.g, if the physician treats When the disease is advanced enough to produce clinical incidental high cholesterol before the patient has any signs or manifestations, it is in the symptomatic stage. Even symptoms of coronary artery disease). However, if the phys stage, the earlier the condition is diagnosed and trea cian considers hypercholesterolemia itself to be a disease more likely the treatment will delay death or serious treating cholesterol levels could be considered secondary pre- cations,or at least provide the opportunity for vention(i.e, treating cholesterol level before fatty atheroma rehabilitation tous deposits form). For hypertension, efforts to lower blood The natural history of a disease is its normal course pressure can be considered primary, secondary, or tertiary the absence of intervention. The central question for studies prevention; primary prevention might be measures to treat of prevention(field trials) and studies of treatment(clinical prehypertension, secondary prevention if the physician is trials)is whether the use of a particular preventive or treat- treating a hypertensive patient, or tertiary prevention for a ment measure would change the natural history of disease patient with symptoms from a hypertensive crisis. in a favorable direction, by delaying or preventing clinical manifestations, complications, or deaths, Many interven tions do not prevent the progression of disease, but instead A. Primary Prevention and Predisease Stage slow the progression so that the disease occurs later in life Most noninfectious diseases can be seen as having an early than it would have occurred if there had been no stage, during which the causal factors start to produce physi Intervention ologic abnormalities. During the predisease stage, athero In the case of myocardial infarction, risk factors include sclerosis may begin with elevated blood levels of the"bad male gender, a history of myocardial infarction, ele- low-densit protein(LDL) cholesterol and may be vated serum lipid levels, a high-fat diet, cigarette smoking, accompanied by low levels of the"good"or scavenger higl sedentary lifestyle, other illnesses (e. g, diabetes mellitus, density lipoprotein(HDL) cholesterol. The goal of a health hypertension), and advancing age. The speed with which intervention at this time is to modify risk factors in a favor coronary atherosclerosis develops in an individual would be able direction. Lifestyle-modifying activities, such as chang modified not only by the diet, but also by the pattern of ng to a diet low in saturated and trans fats, pursuing a physical activity over the course of a lifetime. Hypertension consistent program of aerobic exercise, and ceasing to smoke