what is a disease?

what is a disease?

s infertility a disease? What about obesity, tooth decay, insomnia, alcoholism, small stature, color blindness, kleptomania, or depression? Opinions m...

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s infertility a disease? What about obesity, tooth decay, insomnia, alcoholism, small stature, color blindness, kleptomania, or depression? Opinions might differ, but with disease management being all the rage, case managers might find it interesting that no universally accepted definition of disease exists.' We can certainly identify specific disease entities such as diabetes, coronary artery disease, chronic obstructive p u l m o n a r y disease, and the like. But w h e n w e turn to the theoretical question, "What do all these diseases have in common that makes them diseases?" we find ourselves at a loss. No universal trait or, as philosophers would say, "essence" that all diseases manifest and that explains their "diseaseness" seems to exist. Before going any further, though, it's important to point out that inquiring about the theoretical or conceptual nature of disease is not an arid, academic p u r s u i t - - t h e kind that undergraduates complain about w h e n they wail, "But isn't this just about semantics?" In fact, deciding to call something a disease is often a stimulus for unleashing a sunami of technologic, clinical, political, and especially economic forces. Consider how our reluctance to regard alcoholism as a disease differentiates the degree of resources committed to its sufferers from those committed to a high-profile disease such as Alzheimer's disease. Calling something a disease also has a major effect on social attitudes. Obesity is an excellent example. Do chronically obese people suffer from a disease, or are they just irresponsible gluttons? Some recent research indicates that chronic obesity may indeed be a disease insofar as obese people may lack a brain receptor that tells them w h e n to stop eating? Nonobese persons receive a neurally transmitted "satiation message" that tells TCM 34


them that they're full, but obese persons may not. If it's true, though, that obesity results from a disease, one can envision research efforts to combat it, clinical strategies d e p l o y e d to treat it, and thirdparty payors asked to pay for it. Furthermore, I recall an episode of the television drama "LA Law" (that I suspect was based on an actual case) in which an attorney was suing her firm for dismissing her because she was obese. She argued that she was a good lawyer who did extremely competent w o r k but was let go for (cosmetic) reasons unrelated to her job. The firm countered that its clients did not w a n t her services because they were put off by her size. If she could claim that her obesity was a disease, however, note that she w o u l d not only have a case based in labor law and job discrimination, but she could also claim protection u n d e r the Americans With Disabilities Act. Thus employers might oppose calling obesity a disease for the economic reason that they w o u l d be threatened by the increased job security it could afford certain employees. One last point in justifying an examination of the concept of disease is that medicine seeks to be an exacting science. Consequently, it's important that some sort of agreement exists about the labels we use to refer to clinical conditions. When one considers how we indiscriminately use words such as ailment, syndrome, sickness, illness, malady, and so on, it seems fair to ask what the concept of disease means or, at least, refers to.

Characteristics of Disease It seems that noncontroversial diseases

for the most part manifest the following four characteristics: First, diseases, unlike syndromes, have rather discrete or singular manifestations. Diabetes is easily recognized by hyperglycemia, hypertension by elevated

blood pressure, and osteoporosis by demineralized bone. Presenile dementia, especially of the Alzheimer's type, is quickly suspected by characteristic memory loss or disorientation, whereas the necrotic appearance of gangrene is uniquely striking. Although they may seem conceptually close to diseases, syndromes characteristically have multiple manifestations. AIDS, for example, presents as recurrent infections, skin lesions, physical wasting, and cognitive impairments. We speak about Parkinson's disease, but perhaps we should speak about Parkinson's syndrome because it can present as tremors or ticks, slurred speech, or affected gait. Second, as Whitbeck 3 has observed, diseases tend to be "processual." In fact, they not only exhibit a process, but the process tends to be progressive. Left untreated, type I diabetes proceeds to death, whereas persons w h o ignore their coronary artery disease m a y p a y a steep price for their denial sooner or later. Impairments such as paralysis from spinal cord injury, however, do not exhibit this processual characteristic. Thus we would not say that Christopher Reeve suffers from a disease because fairly straightforw a r d maintenance measures keep him healthy and functional. O n the other hand, if his quadriplegia were the result of a progressively worsening process such as amyotrophic lateral sclerosis or a brain tumor, then we w o u l d be inclined to say he suffers from disease. Third, and very important, all noncontroversial diseases have their origins in pathophysiology. Christopher Boorse 4'5 has championed the notion that virtually all diseases are caused by some cellular or organ system that is not working according to its normal efficiency or design. Indeed, an identifiable, pathophysiologically based abnormality is probably the single most important dis-

CM ETHICS criminator between controversial and noncontroversial diseases. Mental "illness" is an excellent example. Only recently have we come to accept schizophrenia as a disease because we have been able to identify pathophysiological substrates in the brain associated with schizoid behavior. O n the other hand, at least one school of psychotherapy holds that m a n y forms of mental illness are "chosen" by their sufferers? Consequently, we intuitively resist calling these entities diseases because the very idea of choosing to be ill contradicts the w a y cellular or organic dysfunction typically occur involuntarily.

ifestation, processuality, pathophysiologic origin, and public m e n a c e - - a r e , I would argue, exceptionally representative of diseases. To the extent that some clinical malady sufficiently manifests each of these traits, the odds are excellent that we would call that condition a disease. Therefore no singular essence of disease exists but rather a cluster of traits that virtually all noncontroversial diseases display. Problematic diseases, on the other hand, are controversial precisely because of their limited exhibition of these disease traits.

Nondiscriminating Characteristics of Disease

Yet a pathophysiologic process is not the essence of disease because virtually everyone suffers from one or more such processes and would, counterintuitively, be said to be diseased. Male pattern baldness and calcified toenails are of pathophysiologic origin, b u t no great social movement exists that is agitating for their being called diseases. Consequently, a fourth characteristic is necessary; namely, whatever the pathophysiologic process m a y be, a collective social decision must be made that it is sufficiently threatening to h u m a n welfare to merit the designation "disease. "7 N o pathophysiologic process can escape this social estimation of its peril or menace, meaning that cultural v a l u e s - - w h i c h ultimately determine the degree or seriousness of that t h r e a t - - a r e indispensable in distinguishing diseases from nondiseases. Furthermore, because cultural values are relative, what might count as a disease in one culture might not be considered a disease in another. For example, infertility w o u l d hardly attract social concern in an overpopulated country such as China. But in a nomadic tribe whose survival d e p e n d s on an adequate number of individuals being available to replace those w h o can no longer fulfill various social roles, a spate of infertility might i n d e e d be regarded as a disease. These four characteristics--singular manTCM 36


In closing, it's interesting to look at various characteristics that d o n ' t discriminate diseases at all well: 9 Causality is a poor disease discriminator because diseases have widely disparate origins (e.g., genetic, microorganic, or environmental causes) 9 Onset is a poor discriminator because some cancers have an extremely rapid onset whereas others m a y take decades to evolve 9 Disease resolution is extremely variable because some diseases resolve spontaneously but others are thus far incurable 9 Preventability hardly distinguishes diseases from nondiseases because coronary artery disease is largely believed to be preventable whereas m a n y other diseases (especially those of neurologic origin) are not 9 Detectability is a m a d d e n i n g l y inconsistent characteristic of diseases because some are almost immediately detectable (because they cause pain or dysfunction) whereas other diseases (such as prostatic cancer) can be very advanced when they are first detected 9 Symptomatology is likewise inconsistent because some diseases, such as gangrene, are virtually one with their symptoms, whereas other diseases can

manifest themselves in a cloud of inconsistent and ambiguous signs and symptoms Perhaps what is most interesting about the concept of disease is its dependence on a society's estimate of the peril it presents. This might explain w h y color blindness, if it is thought of as a disease at all, would probably be regarded as a very modest one. O n the other hand, questions over whether aging is a disease continue to spark a great deal of scientific and sociocultural controversy. To call aging a disease seems awkward, as well as politically incorrect. Yet some molecular geneticists are intrigued at how the aging process might be a function of the cell's mitochondria, which seems an interesting candidate for housing the internal time clock that controls our b o d y ' s aging (Wallace, 1996, unpublished data). If science learns h o w to slow the aging process, however, our society would then be faced with extraordinarily challenging questions about overpopulation and securing sufficient economic resources to support its aged population. Even if aging has it origins in pathophysiology (which it surely does), some persons will argue that aging is a social good insofar as its end points of biologic decline and death make w a y for the reconstitution of our social order. On the other hand, if old age is increasingly regarded as a horror, we might anticipate more research and clinical activity devoted to its adversities in the hope that we can be "cured" of it. Ultimately, the concept of disease admits considerable plasticity a n d variation. Diseases belong to the societies that identify them and thus are largely created from the cultural fabric of that society. Diseases are perceived according to how that society evolves its philosophy of life and mechanisms of adaptation. Consequently, examining what a society calls disease provides an interesting glimpse into the values of that society itself. "Drapetomani" was a bogus disease nevertheless taken seriously in the nine-

CM ETHICS teenth century. It referred to the tendency of slaves to r u n away from their masters. 7 Ultimately we cannot escape our values. They determine our scientific and clinical aspirations, as well as our responses to w h e t h e r some p h e n o m e n o n merits being called a "disease."

Re||174162174 1. Mersky H. Variable meanings for the definition of disease. J Med Philosop h y 1986;11:215-32. 2. Tartaglia LA, Dembski M, Weng X, et al. Identification and expression cloning of a leptin receptor, OB-R. Cell 1995;83:1263-71. 3. Whitbeck G. Four basic concepts of medical science. In: Asquith PD, Hocking I, editors. Proceedings of the 1978

Biennial Meeting of the Philosophy of Science Association, 1978;1. East Lansing, Mich.: Philosophy of Science Association. 4. Boorse C. O n the distinction between disease and illness. Philosophy and Public Affairs 1975;5:49-68.

John Banja, PhD, is an associate professor of rehabilitation medicine and coordinator of Clinical Ethics Education at Emory University Hospital in Atlanta, Ga. He can be reached at (404) 712-4804.

5. Boorse C. Health as a theoretical concept. Philosophy of Science 1977;44:542-73. 6. Ellis A, Harper R. A new guide to rational living. North Hollywood, Calif.: Melvin Powers, 1978. 7. Engelhardt HT. Health and disease: philosophical perspectives. In: Reich W, editor. Encyclopedia of bioethics. N e w York: Free Press, 1978: 560-99.

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