Orac's just blogged on a new study that seems to show that heavy cellphone use contributes to male infertility. No doubt this will be all over the headlines in a day or so – so I thought I'd get in first & give you some practice in critical thinking while I'm at it.
Here's Orac's summary of the study methods & key findings:
Briefly, the study examined 361 men attending an infertility clinic from September 2004 to October 2005. The mean age of the study population was 31.81±6.12 years. The men were divided into four groups based on their self-reported cell phone usage: none; less than 2 hours a day; 2-4 hours a day; and greater than 4 hours a day. Semen samples were collected, and several standard parameters measured. It was found that there was no correlation between cell phone use and semen volume, liquefaction time, pH, and viscosity. However, a negative correlation adjusted for age was observed between increasing cell phone use and sperm count, motility, sperm viability, and percent normal morphology. The authors concluded that cell phone usage was associated with sperm and semen parameters associated with decreased male fertility.
Yes, that'll make a good headline: Cell phone radiation makes men sterile! But let's take a bit of time to think about this study… (& do read Orac for a more detailed analysis of it.)
My first thought was to do with just how a cell phone might have this effect. After all, most people hold their phones to their heads when making a call. But the strength of an electromagnetic field drops off rapidly with distance from the source (it's inversely proportional to the square of the distance from source). So there would be very little in the way of extra electromagnetic radiation reaching a guy's nether regions when he was making a call.
Orac points out that the four measures of infertility – the number of sperm, how active they are, how well they survive, and how many of them have normal morphology – aren't independent of each other but increase/decrease together. (I wouldn't have known that, not having looked into this particular subject before!). So the researchers weren't really looking at 4 separate measures of male (in)fertility.
And a big problem with the study is – did you pick it? – all the men in the sample were attending an infertility clinic. Given that, when couples seek treatment for infertility, about 50% of the time the problem lies with the male, you'd expect that a large proportion of the study population would be having trouble starting a family.
So – the data & methodology from this project probably don't support the conclusions. But — they do indicate that this is a fertile area for further research…