Do cell phones cause tinnitus?

Forget about cancer caused by cell phones, what about that ringing in your ear? About 10-15% of the adult population suffer from chronic tinnitus. I've had a case of tinnitus after a back injury. Luckily it vanished after 3 months, but since then I'm very sympathetic to people who go nuts from that endless ringing in their ear. A recent study by a group of researchers from Vienna now looked into the correlation between cell phone use and tinnitus. The results are published in their paper Tinnitus and mobile phone use, Occup Environ Med 2010;67:804-808. It's not open access, but do not despair because I'll tell you what they did.

The researchers recruited a group of 100 sufferers that showed up in some hospital in Vienna. They only picked people for whom no physiological, psychological or medical reason for the onset of their tinnitus was found. They excluded for example patients with diseases of the middle ear, hypertension, and those medicated with certain drugs that are known to influence ear ringing. They also did hearing tests to exclude people with hearing loss, of which one might suspect that their tinnitus was noise induced. Chronic tinnitus was defined as lasting longer than 3 months. About one quarter of the patients had had it already longer than 1 year at the time of recruitment. 38 of the 100 found it distressing "most of the time," and 36 "sometimes." The age of the patients ranged from 16 to 80 years.

The researchers then recruited a control group of also 100 people that were matched to the sufferers in certain demographic factors, among others the age group, years of education and whether they lived in- or outside the city.

At the time the study was conducted (2004), 92% of the recruits used a cell-phone. (I suspect the use was strongly correlated with age, but no details on that in the paper). At the time of onset of their tinnitus, only 84% of the sufferers had used a cellphone, and another 17% had used it for less than a year at that time. The recruits, both sufferers and controls, were asked for their cell phone habits by use of a questionnaire. Statistical analysis showed one correlation at the 95% confidence level: for cellphone use longer than 4 years at the onset of tinnitus. In numbers: In the sufferer's group, the ratio between those who had used a cellphone never or less than one year to those who had used it more than 4 years was 34/33. In the control group it was 41/23.

They then discuss various possible explanations, such as the possibility that cell phone radiation affects the synthesis of nitric oxide in the inner ear, but also more banally that a "prolonged contrained posture" or "oral facial manoeuvres" affect the blood flow unfavorably. (Does chewing gum cause tinnitus?)

The result is just barely significant, i.e. just at the edge of the confidence interval. There's a 5% chance of that result happening just coincidentally by unlucky sampling. So the researchers conclude very carefully that "high intensity and long duration of mobile phone use might be associated with tinnitus." Note that it's "associated with" and not "caused by." Needless to say, if you Google "cell phones tinnitus" you'll find several pages incorrectly proclaiming that "The researchers concluded that long term use of a mobile phone is a likely cause of tinnitus," or that the "study suggests cell phones may cause a chronic ringing in the ears." If such a Google search lead you here, the study concludes nothing of that sort. Instead, the authors finish with saying that there "might" be a link and that the issue should be "explored further."

So, do cell phones cause tinnitus? Maybe. Should you stop sleeping with the phone under your pillow? Probably.

In any case, I was left wondering why they didn't ask for phone habits generally. I mean, if it's the posture or movements connected with calling, what's it matter if it's a cell phone or a landline?