What is Disease?

This may sound like a silly question, everyone knows what disease is. But have we ever bothered to define disease, or health for that matter. Right now, in the United States, there is an enormous political debate about “health care delivery” which is, at least ostensibly, about improving the health of the citizens. Is “health” though a commodity which can be delivered by government? Throughout the world, governments have enormous bureaucracies and departments tasked with addressing health and disease such as the National Institutes of Health and the Centers for Disease Control. The US Food and Drug Administration by some estimates regulates some one sixth of the US economy, when it approves a drug it does so based from clinical trials which are intended to show a drug is both safe and effective against a particular disease. So again, why don’t we start at the very beginning and ask just what is disease? When you think about it for a while you begin to realize that, like defining “life”, it is not at all easy to define health or disease.

For example, what a healthy 20 year old and a healthy 80 year old can do are generally much different. If a twenty year old could not run a mile one would worry about disease, if an eighty year old could run a mile we would be impressed. If one has a broken leg, while one is not healthy, I don’t know of any culture that would call them diseased. So, it is not simply diminishment, or even loss of function or ability which defines disease. If the same individual however, had a broken leg not from falling off a ladder but as a consequence of cancer or a genetic condition, then we likely would speak of them as having disease. How about a patient who has recovered from cancer, at what point is the disease no longer “in remission” but instead the person is free of disease? What about carriers of infectious disease such as “typhoid Mary” or someone who doesn’t realize they have tuberculosis, do they themselves have disease? Suppose Typhoid Mary was a hermit who never interacted with others, do they have disease at that point? What about someone with latent or inactive tuberculosis (this is some one third of the world population), they have no effects from tuberculosis, they are not contagious to others, yet, they may have a walled off cyst of live tuberculosis bacteria somewhere in their lungs.

Medical practitioners speak of the “signs” and “symptoms” of disease. The signs of disease are those changes appreciable to the senses which indicate disease. So, for instance, a fever is a sign of disease, the crackles and wheezes heard through a stethoscope are signs of disease. These signs of disease are investigated in the physical exam and other diagnostic tests which may be ordered. The symptoms of disease on the other hand are what the patient is experiencing. So a patient may say, I feel chills, when the physical exam finds a fever, or I am coughing a lot when the exam hears wheezes in the lungs and the x-ray shows a picture of a fluid filled lung, or a child may say that their ear hurts and looking at the ear with an otoscope the nurse or doctor sees an inflamed middle ear. Sometimes, the patient will have symptoms of disease, when no signs of disease can be found, so for instance the patient says, I have a headache and after an exam turns up nothing unusual the doctor says take two aspirin and call me in the morning. Other times there can be signs of disease but no symptoms, so a patient may go for an annual physical and though they feel healthy are told your blood sugar level is very high, you may have diabetes.

I wanted to start with this philosophical look at disease so as to present two arguments. First, Western Medicine generally does a good job treating disease and second most of what Western Medicine does is not treatment of disease. The first point could be argued at length, I would just ask if you had a serious acute disease, say an appendicitis, where would you want it treated? The second point requires some more discussion to be taken seriously. To do this we need to introduce some more medical terminology. A “risk factor” for a disease is something which is believed to place someone at increased risk for a disease. These risk factors may either be something which can’t be changed, such as family history, gender, or presence of a particular gene, or ones which can be changed such as the habit of smoking or having high blood pressure.

These second type of risk factors are called “modifiable risk factors” and over the past half a century a tremendous amount of effort has been placed on attempting to change “modifiable risk factors” so that disease doesn’t occur in the first place. While this is a noble goal, it is also one that is more “risky” than simply treating a disease for a number of reasons. You see, by any definition, someone who only has a risk factor for a particular disease, does not have the disease, therefore whatever “medicine” you are giving is not being given to treat disease it is being given to a healthy person. All medicines carry with them a certain degree of risk and it is a whole different proposition to be giving medicine to a healthy person than to a sick person. If one was diagnosed with an incurable cancer and was told a drug would give them a 50% chance of a cure but would triple their risk of a heart attack or increase their chance of having leukemia in later life they likely wouldn’t give a second thought to taking the drug. If one the other hand, someone was in good health and was told that a drug would give them a 50% less chance of ever developing the cancer but it would triple their risk of heart attack it is an entirely different situation. If instead of preventing the cancer, the drug instead only prevents heartburn or joint pain and has no effect on risk of or progression of disease the risk/benefit scenario is even further skewed away from wanting to take the medicine.

When you give medicine to a sick person it is generally for a very limited period of time, i.e. until they get better. If you rely on a medicine to change a risk factor for disease they may be on it their whole lives. This again greatly increases the possibility of a serious side effect to occur from the medicine. The number of people with a risk factor for a disease will also be much larger than the number of people with the actual disease. This means the number of people on the medicine will be very large and even rare serious side effects may end up affecting a large number of people. Moreover, for any one disease, there may be multiple modifiable risk factors which might be treated pharmacologically. So as is often the case, someone in perfect health may be on multiple medicines to treat various risk factors for disease.

This again increases the possibility of interactions between the various medicines leading to an adverse event. Finally, it is much more difficult to study and determine with any confidence whether treating someone with a risk factor for disease is actually improving their long term health. For one, only a small percentage of the people with a risk factor for disease would be expected to develop the disease so the numbers involved to find any sort of possible difference between treated and untreated groups must be very large. Secondly, the studies must be very long term, over years or decades even to begin to get an idea of who might develop disease. Because of these logistical problems there won’t be a large number of confirmatory studies, and as with any other scientific study one must be concerned about the possibility of bias, especially if one is only relying on a small number of studies. Even if one does improve the risk for developing a disease has one improved overall health. As has often been the case only after a drug has been approved and been given to millions of people does it become apparent that the damage outweighs any benefit.



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