Chronic Disease Prevention CHAPTER OUTLINE cardiovascular diseases(including stroke), cancer, pulmo I. OVERVIEW OF CHRONIC DISEASE 227 ary diseases, and diabetes and related metabolic derange A. The Human Toll 227 ments. These conditions now constitute the leading causes B. The Financial Toll 228 of mortality worldwide. In addition, conditions such as osteoarthritis, chronic pain syndromes, and depression exact I, PREVENTABILITY OF CHRONIC DISEASE 228 a high toll in morbidity and cost, generally without imposing a direct mortality toll III. CONDITION-SPECIFIC PREVENTION 229 Of particular interest to epidemiologists is the strong body of evidence suggesting that fully 80% of chronic disease B. Type 2 Diabetes Mellitus 231 is potentially preventable by means already available, and C. Stroke(Cerebrovascular Accident) 232 that even genetic risk factors for chronic disease develop D. Cardiovascular Disease 232 ment and progression are modifiable by the effective applica E. Chronic Lung Disease 233 tion of lifestyle interventions F. Cancer 233 G. Oral Health 234 A. The Human toll IV. BARRIERS AND OPPORTUNITIES 235 A short list of chronic diseases-heart disease, cancer, stroke A, Impediments to Chronic Disease Prevention 235 diabetes, and chronic lung disease-constitute the leading I. Personal Barriers 235 force of worldwide mortality. More than 60% of all deaths 2. Public Barriers 235 in the world each year are attributable to this short list of conditions. V. SUMMARY 235 In some ways, the mortality toll of chronic diseases can REVIEW QUESTIONS,ANSWERS, AND EXPLANATIONS O exaggerate their harms, Chronic degeneration of vitality and function is, to one des such time as the "rectangularization"of the mortality curve an be converted from an aspiration to prevailing reality (Fig. 19-1). As life expectancy rises, so does the opportunity . OVERVIEW OF CHRONIC DISEASE for time-dependent degeneration of organ systems. Chronic, degenerative disease is simply a point along this spectrum Whereas infectious diseases were long a major determinant and thus inescapable under prevailing conditions if persons of both quality and length of human life, and remain so in live long enough; we must eventually die of something. To much of the developing world, the burden of morbidity and the extent chronic disease merely represents this inevitable premature mortality in developed countries shifted dramati-"something, the attributed death toll can make the situation cally over the 20th century to so-called chronic diseases. The seem worse than the reality. Not succumbing to infectious term"chronic disease"is less useful than in the past because or traumatic causes of death early in life partly makes us even infectious diseases such as human immunodeficiency vulnerable to chronic diseases later. The importance of virus(Hiv) have become chronic" with the advent of effec- causes of death earlier in life is best captured not by the tive treatments in the absence of cure. In essence, any disease number of deaths but by the number of years of potential life that can be effectively managed over years or decades, but lost(see Chapter 24) not cured is chronic. The term chronic di plied In another important way, however, the mortality toll of referentially, however to conditions described as follows: greatly underestimates Not directly transmissible person to person Long before taking years from life by causing premature a Routinely span years and often decades death, chronic diseases take life from years by reducing ability, a Degenerative in some way, relating to aberrant or declin function, vitality, and quality. This is an ever more salient ng function of some body part or system concern because chronic diseases, driven largely by a short a Often propagated by fundamental physiologic imbalance list of lifestyle factors and particularly their relationship to or disturbances, such as inflammation obesity, occur at ever younger ages. What was called only a generation ago"adult-onset diabetes" is now called type 2 The conditions of greatest concern--contributing most diabetes and routinely diagnosed in children. The prolifera to years lost from life, life lost from years, and costs-are tion of cardiac risk factors in ever younger children is we
228 SECTION 3 Preventive medicine and public Health Advances in pharmacotherapy and technology tend to improve treatment and function(favorable)but generally involve higher costs(unfavorable). The positive message lost in gloomy statistics about cost is that we are getting what we are paying for": longer lives despite the high and rising prevalence of chronic disease Other messages related to the financial costs of chronic Disability-free survival disease are decidedly less positive As addressed later, chronic diseases are substantially preventable by means already avail ble. The reliance on high-cost treatment is to some degree testimony to the failure to make better use of lower-cost prevention. There is also widespread failure to treat risk factors such as high blood pressure and dyslipidemia to Death ta Also, the direct financial costs of chronic disease care do The gray line represents the survival curve for a population. not fully capture the economic toll. Reduced productivit absenteeism, presenteeism(attending work while sick), and The blue lines represent varying levels of disability related effects, known in economic terms as externalities or amond survivors indirect costs(or benefits; externalities can be positive as well Squaring the curve via prevention or health promotion as negative), are high and may even exceed the direct costs implies shifting these curves upwards, towards the Projections about the financial costs of chronic disease hypothetical population health limit represented by the black are genuinely alarming and constitute nothing less than a crisis, questioning the fundamental solvency and economi viability of the U.S. health care system beyond the middle of 9-I The concept of rectangularizing, or squaring, the the 21st century should current trends persist. As a result, curve( From Society, the individual, and medicine, Ottawa here is increasing awareness about the importance of oio,UniversityofOttawawww.med.uottawa.ca/sim/data/ chronic disease prevention and the strategies that will convert what is known in this area into what is done, as well as increased attention to better management of chronic disease with patient-centered medical homes and the chronic care documented. Further, the occasional lifestyle-related cancer model. Professionals directly involved in public health and is diagnosed in surprisingly younger persons. A marked preventive medicine have a clear opportunity to advance the increase in the rate of stroke among children age 5 to 14 years mission of prevention in responding to the dangers of the also has been reported. chronic disease crisis Collectively, these trends indicate the importance of fac toring the chronicity of chronic disease into any assessment C. Common Elements in Pathogenesis of the human cost. As serious and potentially disabling disease begins at ever-younger ages, mortality becomes an There is increasing appreciation for a unifying constellation increasingly less useful measure of the total impact of these of processes that underlie most if not all chronic degenera conditions. A measure of attenuated quality of life, adjusted tive diseases. 4 These pathways and their details will spawn for the life span affected, is most suitable@(See Chapters 14 discussion and debate for years. A case may be made, however, nd 24 for quality-adjusted life years [QALY] and disability- for a short list of common pathways, as shown in Box 19-1 d justed life years [DALYT) By such a metric, the human cost Of particular relevance in the context of epidemiology is of chronic disease is enormous and it continues to rise. that a common constellation of factors underlying most or all chronic di B. The financial toll case; the same short list of lifestyle factors appears to influ There are glib expressions in the halls of medicine about the ence the likelihood of all major chronic diseases across the relative financial costs of life and death. Death is, in financial life span, other factors being equal(see Box 19-2). The terms, inexpensive as expenditures related to treatment and notion of common pathways to diverse morbidities has been preservation of life cease. Life, burdened by chronic disease, embraced by leading health agencies and the National can be enormously ex grow ever m Institutes of Health(NIH). 6 at forestalling death through the application of pharmaco therapy, procedures, and medical technology, the costs of living with chronic disease are rising. In the United States, I. PREVENTABILITY OF CHRONIC DISEASE more than 75% of Medicare expenditure(hundreds of bil lions of dollars annually) is for chronic disease Literature spanning at least the past two decades makes a As with the mortality statistics, these costs represent compelling case that the leading causes of premature death- several mixed messages. The positive message is that costs of and thus the leading causes of chronic morbidity, because hronic disease care rise as this care becomes more effective. they are the same -are overwhelmingly preventable by When treatments are ineffective, death comes earlier. M means already available. A seminal 1993 paper first high effective treatment is unquestionably good, but means a lighted that chronic diseases leading to premature death were longer treatment period before death and thus higher costs. not meaningfully "causes"of death but rather "effects
CHAPTER 9 Chronic Disease Prevention 229 Box19-1 Four Pathophysiologic Pathways in Chronic Disease I. Cellular Senescence 3. Oxidation Aging, or senescence, at the organ system and cellular levels encom ation with the health-promoting potential of antioxi asses gradual attenuation of function (.g, age-related decline in es from the harmful potential of oxygen free radicals glomerular filtration rate)and ultimately a termination of cellula both in defense of the body against pathogens and as a renewal and the loss of formerly functional cells through apoptosi t of metabolic activity, Oxidation is implicated as a facilita rogrammed cell death). Chronologic and biologic aging are related but different, Chronologic aging refers to a measure in units of actua time, biologic aging refers to function relative to age-standardized 4. Inflammation norms By either measure, the time-dependent attenuation of func- Inflammation is a generic term referring to a range of immune tional capacity is a common element in the development and pro- gression of chronic diseases. system actions, both in response to and independent of infection. The action of various white blood cell lines, cytokines, immu globulins, and 2. Degeneration complement can defend the body against pathogens but can also cause damage to native tissue and healthy cells. Dietary Degeneration can occur as a time-dependent process but can also occur imbalances, with resultant hormonal imbalances, related in particu independently. Cumulative injury to the lining caused by lar to eicosanoids(prostaglandins), cortisol, and insulin, are impli- hypertension is an example of degeneratio theerosion of articu- cated in chronic inflammation, which in turn is implicated in the lar cartilage caused by"wear and tear" that osteoarthritis propagation of most chronic disease. Common to most if not all chronic diseases. These processes provide important insights about the potential to prevent chronic disease, as well as opportunities to prevent multiple chronic diseases by addressing a common cluster of causes ox 19-2 Ten Controllable Factors in %o of cancer are thought to be preventable with the use of resources already Prevention of Chronic Disease available. Were this knowledge to be translated into the power of routine action, it would increase life expectancy Toxic agents and add much more to health expectancy, or the health Firearms span. 4 In blunt terms, if and when we find the means to Activity patterns exual behavi Motor vehicles turn what we know about the prevention of chronic disease Microbial agents into what we routinely do, it would constitute one of the most stunning advances in the history of public health(see Chapter 28) Modified from McGinnis JM, Foege WH: JAMA 270: 2207-2212, I. CONDITION-SPECIFIC PREVENTION A. Obese These effects-the chronic diseaseswere the result of 10 There is debate about the appropriateness of classifying factors, mostly behaviors that individuals can control(Box obesity as a chronic disease. Obesity is clearly established as 19-2). Using the epidemiology of 1990, this analysis found a risk factor for virtually all major chronic diseases. Whether that about 80%of all premature deaths were attributable to obesity itself qualifies as a disease is important in several the first three entries: tobacco, diet, and activity patterns ways. First, obesity bias is a prevalent and pernicious influ- (physical activity ). Alliteratively, the leading causes of chronic ence, and the establishment of obesity as a true medical disease and premature death in 1990 were "how we used our condition defends against this in the form of legitimacy. The feet, our forks, and our fingers codification of obesity as a disease implies that, as with other In 2004 the U.S. Centers for Disease Control and Preven diseases, it is (at least relatively) inappropriate to"blame the tion(CDC)updated and supported the same fundamental victim. Studies, on in adi, recent and ac umulating evidence identification of obesity as a disease facilitates its inclusion indicates that lifestyle interventions can modify gene expres among conditions with medical insurance coverage. The sion and thus alter the risk for chronic disease development International Classification of Diseases(ICD) coding system and progression at the genetic level. 2 In the aggregate, this used for billing third-party payers assigns a"diagnostic code' re belies the importance of the nature/nurture debate to any given condition. Obesity must be recognized among slighting the hegemony of " epigenetics"and the candidate conditions for such coverage to be processed. The apparent human potential to"nurture nature U.S. Department of Health and Human Services initially he available data from diverse sources suggest that about desi disease with this in mind, and rele. 80%of all chronic disease could be prevented. with regard vant progress has followed. In 2011 the Centers for Me to specific conditions, 80%or more of cardiovascular disease; and Medicaid Services( CMS)authorized reimbursement for
230 SECTION 3 Preventive medicine and public Health obesity counseling to physicians treating patients with a The importance of this perspective is in how it relates to body mass index(BMI)of 30 or greater(Table 19-1 prevailing societal responses. The treatment of drowning There is a potential liability, however, in cataloging obesity after it occurs is relatively rare and far from optimal. Many a disease. Diseases are states of aberrant body function to teaching children how to swim, to putting fences around generally amenable to medical treatments (e.g., pharmaco therapy, surgery). If obesity constitutes such an aberrant pools--to prevent drowning from occurring. Only when the state,it invites a focus on such treatments as bariatric surgery clear emphasis on environmental approaches to prevention and antiobesity drugs. The effectiveness of bariatric surgery fails does the treatment of drowning become germane, as a is well established and the pursuit of effective drugs for last resort weight management well justified, but a dedicated focus on hroughout most of human history, calories have been these approaches can and likely does distract attention and relatively scarce and often difficult to obtain, and physical divert resources from policies and programs that facilitate activity has been an unavoidable requirement for survival better use of feet and forks. In other words, by blaming Modern society has devised an environment in which physi obesity on a diseased state of the body, the potential to cal activity is scarce and often difficult to maintain, and calo- address the diseased state of the obesigenic(obesity-causing ries are unavoidable. Homo sapiens are endowed with no environment may be diminished native defenses against caloric excess and the tend An analogy well suited to clarify this perspective is dr toward "sedentariness The result is the modern obese ing. Drowning is a legitimate medical condition for trends In essence, the population is confronting an environ medical care is warranted and for which both diagnostic ment for which it is poorly suited and is succumbing to its codes and reimbursement are available. However, no one toxic effects. We are drowning in calories. This perspective mistakes the propensity to drown as an"aberrant state of might promote an emphasis on environmentally based the body. Rather, a perfectly normal and healthy body is approaches(policies and programs that facilitate healthful simply not suited to breathing under the water. Drowning eating and routine physical activity)to obesity prevention (or near-drowning) is recognized universally as the inevita- and control, even while establishing the medical legitimac ble outcome when a normal body spends too much time in of obesity as a condition deserving treatment( Box 19-3 an environment(underwater) to which it is poorly suited Nonmodifiable risk factors for obesity include low resting energy expenditure, genetic polymorphisms that predispose to weight gain and impede weight loss, and an ethnic heri- Table 19-1 CLassification of Weight Status Based on Body tage that increases the propensity for obesity. Modifiable risk Mass Index(BMD) factors relate principally to the quality and quantity of dietary intake and energy expenditure through exercise. Lean BMI* Classifcation body mass can be increased through exercise and thus also constitutes a modifiable risk factor. Insomnia increases obesity risk by several mechanisms, and thus impaired sleep is a potentially modifiable risk factor as wel The primary and secondary prevention of obesity prind 30-34.9 35-399 pally involve Stage Ill(severe)obesity terns. Secondary prevention includes screen means clinical assessment of weight and height(BMI)as well pressed as weight in kilograms divided by the square of the height in meters as waist circumference, and for children the plotting of BMI on appropriate growth charts. Box 19-3 Summary of Obesity Risk Factors and Prevention Secondary Prevention Screening: Assessing body mass index(BMI)and waist Resting energy expenditure/basal metabolic rate cren ce in clinical practice; plotting pediatric BMI or growth charts licit Physical activity promotion ww Possible use of pharmacotherapy Tertiary Prevention Sleep quality and quantity Bariatric surgery Pharmacotherapy Primary Prevention Dietary management and physical activity promotion as important Dietary management: improved quality, control of quantity dividuals.Tertiary prevention is for symptom o prevent them from becoming obese. Secondary prevention is for asymptomatically obese Primary prevention is for nonobese indi
CHAPTER 9 Chronic Disease Prevention Tertiary prevention, to prevent complications B. Type 2 Diabetes Mellitus lished obesity, often involves pharmacotherapy for complications and bariatric surgery. The utility of In developed countries, about 95% of patients with surgery is well established. Pharmacotherapy for obesity is mellitus have type 2. Whereas type 1 diabetes is an to date, of limited utility and prone to unintended conse- mune disease resulting in destruction of the quences. The use of medications for the metabolic complica- producing beta cells of the islets of Langerhans, type 2 tions of obesity, such as prediabetes, is more clearly supported diabetes is overwhelmingly a lifestyle-related disease of pro ressive insulin resistance mediated largely by excess body Figure 19-2 shows the prevalence of obesity in low- fat. Type 2 diabetes mellitus, formerly called"adult-onset income U.S. children age 2 to 4 years diabetes, is usually preventable, both by treating the insulin See Figure 19-3 on studentconsult. com for obesity trends resistance that often precedes it and, more fundamentally, by U.S. adults. ( For USPSTF recommendations on obesit preventing the accumulation of excess visceral fat that is an see the Websites list at end of chapter. Important root if not the cause, in most patients. 7 The importance of preventing type 2 diabetes is reflected in its large contribution to current health care costs and LoW-Income Children Aged 2 to 4 Years of its fut that as many as one in three americans will have diabetes 圖口回■□ by the mid-2lst century if current trends persist, putting the fate of the U.S. health care system in doubt. Fortu nately, type 2 diabetes is overwhelmingly preventable by available interventions. A fasting glucose between 100 and 125 mg/dL is indicative of prediabetes, whereas a level of 126 mg/dL or greater indicates diabetes. The U.S.Preven tive Services Task Force(USPSTF) specifically recommends diabetes screening in patients with borderline or overt Risk factors for type 2 diabetes overlap substantially with risk factors for obesity. Rates of diabetes are considerably higher in some ethnic groups than others, and there is a known genetic predisposition. The principal driver of the epidemiology of type 2 diabetes, however, and its progression from a disease of adults into a disease of children and adults alike, is epidemic (or hyperendemic)obesity ● Inter Unbal concl ot Anmon●Sa o Navao Nation(AZ, NM, The epidemiology of obesity has changed drastically Viroin blands over recent decades; genes have not. In particular, central adiposity and the accumulation of excess visceral fat in the Figure 19-2 Obesity prevalence in early childhood, united States, liver are causally implicated. Diabetes can be prevented 2009. Among low-income children age 2 to 4 years by state. Insert, In with lifestyle interventions that foster moderate weight loss territories and Indian tribe organizations. ( From Division of Nutrition with pharmacotherapy; and with bariatric surgery. Medical Physical Activity and Obesity, National Center for Chronic Disease management of diabetes to prevent progression and compli Prevention and Health Promotion, Atlanta. 2009. uS Centers for Disease cations constitutes tertiary prevention Box 19-4 summarizes Control and Prevention.) Box 19-4 Summary of Type 2 Diabetes Risk Factors and Preventie Risk Factors Physical activity Nonmodifable Pharmacothera Genetics ity, in particular abdominal (visceral)adios Medical assessment for potential complications(e.g, eye and foot Primary Prevention Bariatric surgery Weight loss/management Weight loss/management Physical activity Pharmacotherapy Bariatric surgery Dietary management