Doctor says ‘The cause is unknown’
The story is told of a final-year medical student who went for an oral examination. He had nearly failed the examination and his fate would be decided by the next question he was going to be asked. If he got it right, he would pass. If he failed to answer correctly, that would be the end of the road for him, having spent almost seven years in school. He was to give the cause of a disease.
Advertisement
As fate would have it for a failing student, he did not know the answer. After thinking about it for a few seconds, he mustered courage and told the examiner that he did not know. To his amazement, the examiner told him he had passed the examination, the reason being that the exact cause of the condition was unknown.
Primary causes
The truth is that there are a number of diseases whose primary causes are not known. For example, someone can develop hypertension or cancer without any known cause. For such diseases, we can only talk about secondary causes or risk factors which increase the person’s chance of contracting the disease.
Removing the risk factor of a disease reduces the person’s chance of contracting the disease but does not make him immune to that disease.
A lot of patients, unfortunately, do not ask questions about the condition of the disease and its management. Only a few patients will probably ask the doctor about the cause of their illness or the side effects of the drugs prescribed for them. If you belong to the latter group, then you may have been told that a lot of diseases have no known cause.
Estimating risk factors
Two research methods are commonly used to assess risk factors of a disease. In case-control studies, people who have already had the disease (e.g. lung cancer) are assessed to ascertain whether or not they have ever come into contact with the risk factor (e.g. smoking) in the past.
In the other study (cohort study), people who have been exposed to the risk factor are followed for a period of time to see how many will develop the disease.
A similar (control) group comprising those who have not been exposed to the risk factor are also monitored to see how many will develop the disease, for comparative analysis.
At the end of the study, it is the difference in the proportion of those exposed to the risk factor who developed the disease and the proportion of those not exposed to the risk factor who also developed the disease that shows whether the factor being investigated is associated with the disease or not.
Thus, if the difference in rates between the two groups is zero, then there is no increased risk for being investigated.
The ratio of the two rates can also be used to ascertain the relative risk. Thus, if the proportion of those who were exposed to the risk factor who developed the disease is 80 per cent and the proportion of those not exposed to the risk factor who developed the disease is 20 per cent, then the relative risk is four times. This means that the factor being investigated is four times more likely to be associated with the disease.
The greater the relative risk, the more likely the factor being investigated is the causative agent for the disease.
Implication
From the ongoing discussion, it can be inferred that you can still develop a disease even if you are not exposed to the risk factor, albeit your chance of contracting the disease is reduced. It is also possible that there may be multiple risk factors to a particular disease or, simply put, the actual or real cause may not be known.
The fact that the primary cause of a disease may not be known also makes its eradication difficult. Patients often ask when they are going to stop medication for their hypertension or diabetes. They often get disappointed when they are told that they would have to manage their condition for life.