Just about every time I use a cell phone, I plug in my wired earpiece first. Having discussed the use of earpieces on several news shows, people expect to see me using one. If I am walking around the CNN studios, my colleagues often comment on it. In airports, people will stop me in the rare cases I forget to use the earpiece, and remind me about it. Perhaps, they are intrigued because I am a neurosurgeon who openly shows some concern about cell phones.

Truth is, it is a pretty easy thing to do – using an earpiece. Furthermore, my neck doesn’t hurt after being on the phone for a long conference call, and given that many of those calls take place in a car, an earpiece becomes a requirement. Still, though, I don’t want to dodge the obvious question: Do cell phones cause brain cancer?

It may be too early to say for sure. The latency period or time between exposure and recognition of a tumor is around 20 years, sometimes longer. And, cell phone use in the U.S. has been popular for only around 15 years. Back in 1996, there were 34 million cell phone users. Today there are 9-10 times as many. Keeping that in mind, it is worth taking a more detailed look at the results of Interphone, a multinational study designed to try to answer this question.

The headline from this study was there was little or no evidence to show an association between cell phones and cancer. Though, if you went to the appendix of the study, which interestingly was available only online, you found something unsettling. The data showed people who used a cell phone 10 years or more doubled the risk of developing a glioma, a type of brain tumor. And, across the board – most of the studies that have shown an increased risk are from Scandinavia, a place where cell phones have been popular since the early 1990s. For these reasons, the whole issue of latency could become increasingly important.