Cell phones don’t cause blinding either

According to a preliminary study in the Journal of the American Medical Association –  “Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucose Metabolism” (Volkow et al. 2011) – the radio frequency emissions from cell phones can cause detectable changes in the metabolism of a specific brain region.

In healthy participants and compared with no exposure, 50-minute cell phone exposure was associated with increased brain glucose metabolism in the region closest to the antenna. This finding is of unknown clinical significance.

While there has been a great deal of speculation in the media regarding the mechanism of this effect, we need to dedicated some thought to whether there is actually an effect that requires explanation.

Now, I lack the expertise to question the quality of the PET scans or the statistical significance of the change in metabolism between the cell phone “off” and “on” conditions and am, therefore, perfectly happy to accept that there is a statistically significant difference in PET signal between the “on” and “off” condition. That is not the same as saying I accept that cell phone emissions caused the effect.

My doubt is based on concerns about the quality of the blinding in this study. Blinding refers to the practice of disguising the conditions of an experiment. Placebos that look, taste, and have similar side effects to pharmacologically active pills in drug studies are a form of blinding that disguises which treatment a subject is receiving. Blinding can be applied to both subjects and researchers.

Because the effect size is so small, any problems with the blinding of this study could introduce biases that could have affect the brain’s metabolic activity, instead of the RF emissions.

In order to accept the study’s conclusion, we need to believe that the subjects were completely ignorant of when the “on/off” state of the  phone. The paper states that “on/off” state was randomized and that the subjects were blinded to the “on/off” state. They do not report the effectiveness of the blinding (i.e., how well could the subjects guess is which test the phone was “on”).

It does not seem at all improbable to me that the subjects may have had some awareness of the “on/off” state of the phone (not necessarily conscious awareness). For example, phones generate heat as they use battery power and run electricity through wires with resistance. When broadcasting, they use more power than when they are not. Small temperature differences between the “on” and “off” states could subvert the attempts at blinding.

While phones were placed next to both ears of the subjects, only the phone next to the right ear was turned on. The vast majority of subjects (80.9%) typically use their own cell phones against their right ear. This trend could make a directionally biased result possible if the subjects had any awareness of the “on/off” state.

The article does not state that the researchers were blinded at the time of testing. Indeed, it seems that they were not, as they actively monitored the RF emissions during the experiment to make sure the phone continually broadcast. This raises the possibility that the researchers may have inadvertently signaled the “on/off” state to the subjects. This type of influence can be very hard to avoid and is one of the reasons for rigorous, double blinded drug trials.

The reported difference from this study, although statistically significant, is very small. The media have focused on the mysteriousness of the effect as if this is the first study in a new and important field of research. It may be. But, in this case, it means that all the results and conclusions are preliminary. They need to be replicated in larger sample sets and with unimpeachable methods, if upon longer reflection these preliminary findings are deemed worthy of follow-up.

Author: Josh Witten

http://www.thefinchandpea.com

One thought on “Cell phones don’t cause blinding either”

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s