Saturday, April 14, 2012
Dental X-Rays and the Risk of Brain Cancer
"This study is fraught with troubling variables that, on their own cast significant doubt as to the validity of the study, but when compounded really degrade the veracity of any of its findings.
Let's just talk about five:
FIRST: This is a self-reported study. This study doesn't examine ANY dental records. Only medical records are used, and this is only to identify the tumor cohort. As such, the study soley relies upon the memories of subjects going back before the age of ten. Let's think for a moment about an individual who unfortunately has been diagnosed with a brain tumor. A tough, tragic and shocking diagnosis to anyone. Even before contacted by examiners to participate in the study, I wouldn't be surprised if those with tumors hadn't already spent a lot of time thinking about why they might have had a brain tumor. More than any other tumor in the body, thinking about dental radiation would be a natural mental exercise. Thinking about ANY radiation around the face, head and neck in an individuals past would be something I would expect from any patient with a brain tumor. Now, have an examiner call by phone, and spend 50 minutes discussing their history of dental x-rays.... it wouldn't surprise me at all to think that the bias in the patient would lean towards a more acute recollection of dental x-rays. Think about it as compared to an individual control who never gave it any thought at all until the examiner posed the dental x-ray questions. THE COMPARISON OF THESE TWO COHORTS OF PATIENTS BASED ONLY ON PERSONAL REPORT SHOULD RAISE SERIOUS QUESTIONS AS TO THE VALIDITY OF THIS STUDY.
SECOND: The time span which this study encompasses includes (and heavily weights) radiation delivered prior to the common use of digital radiography or even faster speed films. In my opinion it is safe to say that radiation delivered today is a fraction of what it was during the scope of time covered with this study. THIS FACT ALONE SHOULD ALLOW ALL PRACTITIONERS TO CONFIDENTLY DISCUSS THE DIFFERENCE BETWEEN TODAYS RADIOGRAPHIC STUDIES VS. THE CONCLUSIONS DERIVED FROM THIS STUDY.
THIRD: NO CORRELATION BETWEEN CT STUDIES AND MENINGIOMAS WAS MADE WITH THIS STUDY. QUOTING FROM THE STUDY "TO OUR KNOWLEDGE, NO STUDIES HAVE REPORTED ON THE ASSOCIATION BETWEEN USE OF COMPUTED TOMOGRAPHY (CT) AND MENINGIOMA RISK.... IT IS NOTEWORTHY THAT CASES (OF MENINGIOMA) WERE NO MORE LIKELY TO HAVE RECEIVED A HEAD CT THAN CONTROLS."
FOURTH - AND THE MOST TROUBLING FOR THE AUTHORS OF THE STUDY: There was a statistically significant increased risk of meningioma for patients who reported having bitewing radiographs, yet no statistically significant increase for patients with full-mouth films. THIS CONFOUNDING FINDING IN THE STUDY IS NOT ADDRESSED BY THE AUTHORS, AND FLYS IN THE FACE OF THEIR CONCLUSIONS. VERY, VERY TROUBLING, YET NEVER ADDRESSED. IT MAKES NO SENSE WHATSOEVER.
FIFTH (CIRCLING BACK TO THE FIRST) - The problems with this study are discussed in the paper: "Limitations of this study include the possibility of either under-reporting or over-reporting of dental x-rays by study participants." YA THINK? WHAT IF UNDER REPORTING BY HEALTHY INDIVIDUALS AND OVER REPORTING OF AFFECTED INDIVIDUALS OCCURRED IN THIS STUDY? IT CAN'T BE AND ISN'T DISPUTED IN THE PAPER THAT THIS IS POSSIBLE. WHAT IF THE OVER/UNDER REPORTING BIAS ERASES ALL STATISTICAL SIGNIFICANCE?
The only strength in the study is the number of patients. Large numbers gives any study statistical POWER. Yet without truth in the variate, even POWERFUL studies aren't valid."
I hope you find this information helpful and that you share it with friends and family members. It is important to note that not all research is created equal and that we always have to question new findings and not automatically accept everything we here as fact, even if it comes from Yale.