Dr. Tsubokura's Radiation Lecture Vol.113

Author: Masaharu Tsubokura M.D., PhD.

Editors: Akihiko Ozaki M.D.,PhD., Yuki Senoo


225. Extra Attention Should Be Paid to the Figures Used to Express Numbers of Patients Developing Certain Diseases in the Post-disaster Period

When researching the post?nuclear disaster public health situation in Fukushima, you may encounter many figures used to express whether the number of patients with certain illnesses has increased or decreased. While these figures enable us to comprehend the current circumstances at a glance, one must be aware of several things to understand what these figures represent.


Let’s take the common cold as an example. Some people get major cold symptoms and go to the hospital, while others prefer to stay home to rest until they recover. Some may have only minor symptoms and go to work without realizing that they have a cold. From this example, it is apparent that the number of people who had caught a common cold is much larger than the number of people who visited the hospital for a cold.


    Thus, the number of people who visited the hospital for a cold could be obtained by checking patients’ records. However, we could only determine the total number of people by asking people individually. What do you think would happen if we conducted individual surveys to confirm the total number of people who caught a cold? The answer is that the number of people with a cold in the sampling year will be greater than the number of people who visited the hospital due to a cold in the same year. This is because many people do not visit the hospital for a cold.

    As a result, if hospital visit data were used to calculate the number of patients who developed a cold in previous years, a simple comparison of this data with the sampling year would look as if the number of those who developed a cold increased. This is the same for investigations of other diseases as well. Therefore, extra attention should be paid when reading a paper reporting that the occurrence of certain diseases increased after the nuclear disaster.


226. The Numbers of Patients Are Collected Separately from the Patients’ Records at Hospitals

    When researching the post?nuclear disaster public health situation in Fukushima, one may encounter many figures used to express whether the number of patients with certain illnesses has increased or decreased. While these figures enable us to comprehend the current circumstances at a glance, one must be aware of several things to understand what these figures represent.


   After the nuclear disaster in 2011, many people in Fukushima Prefecture had to change their local GP because some hospitals and local clinics were forced into closure. As patients see multiple medical institutions for the same conditions, it looks as if those conditions increased in the area.

 

   For example, say a patient has a certain type of cancer and changed hospitals after the Fukushima Daiichi nuclear disaster in March 2011. To maintain the patient’s privacy and confidentiality, the hospital cannot easily disclose the patient’s information to third parties. As a result, when researchers investigate the number of people with cancer in the area, the same patients will be double-counted because they were included in the figures for the first and second hospitals they visited. This increases the total number of patients with cancer.


   In addition, when new doctors are assigned to hospitals in Fukushima Prefecture, the number of diseases that can be treated in the prefecture increases accordingly. This will also attract more patients to the hospitals; as a result, it may seem as if the occurrence of certain diseases within the community has increased.


   This goes the same way as with any other disease. When we see phrases such as “the number of diseases has increased XX times” in a paper, we must be careful about what they indicate.



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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, 5th and 12th May 2019 was reproduced for MRIC Global under the author's permission.

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