Thursday, May 7, 2015

Heavy Use of Cell Phones & Cordless Phones Increases Brain Tumor Risk

Pooled analysis of Swedish case-control studies during 1997-2003  and 2007-2009 on meningioma risk associated with the use of mobile and cordless phone

Michael Carlberg, Lennart Hardell. Pooled analysis of Swedish case-control studies during 1997-2003  and 2007-2009 on meningioma risk associated with the use of mobile and cordless phone. Oncology Reports. 33:3093-3098. 2015. DOI: 10.3892/or.2015.3930


A pooled analysis of two case-control studies on meningioma with patients diagnosed during 1997‑2003 and 2007-2009 was conducted. Both genders were included, aged 20-80 and 18-75 years, respectively, at the time of diagnosis. Population-based controls, matched according to age and gender, were enrolled. Exposure was assessed by questionnaire. In the entire study, cases with all brain tumor types were included. The whole reference group was used in the unconditional logistic regression analysis on meningioma, with adjustments for gender, age, year of diagnosis and socioeconomic index (SEI).

In total, 1,625 meningioma cases and 3,530 controls were analyzed. Overall no association with use of mobile or cordless phones was found. In the fourth quartile of use (>1,436 h) somewhat increased risk was found for mobile phones yielding an odds ratio (OR)=1.2, 95% confidence intervals (CI)=0.9‑1.6 and cordless phones OR=1.7, 95% CI=1.3-2.2. Higher risk was calculated in the highest decile (>3,358 h), OR=1.5, 95% CI=0.99-2.1 and OR=2.0, 95% CI=1.4-2.8, respectively. In addition, the longest latency time gave somewhat increased risk for both phone types although the result was not statistically significant. There was no association for ipsilateral use or anatomical tumor location.

The present study showed a somewhat increased risk among heavy users of mobile and cordless phones. Since meningioma is generally a slow-growing tumor, longer latency period is necessary for definitive conclusions.


Meningioma is most common among middle-aged and elderly individuals. The incidence is approximately 2-fold higher in women than in men (1,2). It accounts for approximately 30% of intracranial tumors (3) and develops from the pia and arachnoid membrane that cover the central nervous system. Meningioma is a benign, encapsulated, well-demarked and seldom malignant tumor. It is slow growing and presents with neurological symptoms by compression of adjacent structures. Headaches and seizures are common symptoms.

The only well-established risk factor is ionizing radiation with a long latency period (time from first exposure until diagnosis) encompassing decades (4,5). Sex hormones may be of importance due to the female predominance, yet the role is unclear and has been suggested not to fully explain the higher incidence in women (6).

During recent years, the use of wireless phones has been discussed as a risk factor for brain tumors. When used they emit radiofrequency electromagnetic fields (RF-EMFs).

The Nordic countries were among the first in the world to widely adopt this technology. Analogue phones (NMT; Nordic Mobile Telephone System) were introduced in the early 1980's ...

The digital system (GSM; Global System for Mobile Communication) using dual band, 900 and 1,800 MHz, started to operate in 1991. The third generation of mobile phones, 3G or Universal Mobile Telecommunication System (UMTS), using 1,900/2,100 MHz RF fields has  been introduced worldwide in recent years, and in Sweden in 2003 and currently dominates the market.

Desktop cordless phones (DECT) have been used in Sweden since 1988, first using analogue 800-900 MHz RF fields, but since the early 1990's using a digital 1,900-MHz system. The cordless phones are becoming more common than traditional telephones connected to landlines. In addition, these phones emit RF-EMF radiation similar to that of mobile phones.

[In 2011,] ... Regarding meningioma, the IARC Working Group found that the available evidence was insufficient to reach a conclusion on an association with mobile phone use (7). The only studies that provided results for a 10-year latency or more were those from the Hardell group (9,13) and the Interphone study group (12).

Cumulative use. ... Cordless phone use gave statistically significant increased risk in the fourth quartile to OR=1.7, 95% CI=1.3-2.2 (p-trend <0.0001). Total use of wireless phones >1,486 h gave OR=1.3, 95% CI=1.1‑1.6 (p-trend =0.01). We also analyzed the >90th percentile corresponding to >3,358 h cumulative use. Mobile phones of the digital type (2G and 3G) gave a borderline increased risk with OR=1.5, 95% CI=1.0005-2.3 (p-trend =0.045) and cordless phone gave OR=2.0, 95% CI=1.4-2.8 (p-trend <0.0001; data not shown). The results for analogue mobile phones were based on only 6 exposed cases and 8 exposed controls yielding OR=2.1, 95% CI=0.7-6.3 (p-trend =0.65). Somewhat increased risk was found for the different phone types per 100-h cumulative use (Table II). Mobile phone use in total gave OR=1.005, 95% CI=1.001-1.009 and cordless phone use OR=1.010, 95% CI=1.005-1.014.

Multivariate and conditional logistic regression. ... The risk increased with statistical significance for cordless phone use with OR=1.009, 95% CI=1.004-1.013 per 100-h use ...

A modest increased risk was found in the fourth quartile >1,486 h of cumulative use for mobile phones. The result was statistically significant for cordless phones with a statistically significant trend (p<0.0001). We also analyzed the >90th percentile of cumulative use which gave support for an association with use both of mobile and cordless phones. In the multivariate analysis, only cordless phone use remained as a statistically significant risk factor per 100 h of cumulative use. The risk increased somewhat per year of latency for all phone types but was not statistically significant. Thus, taking together the results for mobile phones and cordless phones, an increased risk cannot be excluded among the heaviest users.

In the French case-control study including the time period 2004-2006, an increased risk was found among the heaviest mobile phone users (18). Thus cumulative use >896 h gave OR=2.57, 95% CI=1.02-6.44 for meningioma (p-trend =0.06). Time since first use >10 years yielded OR=1.57, 95% CI=0.64‑3.86 (p-trend =0.52), whereas no increased risk was found for shorter time of use. Use of cordless phones was not assessed. The study provided some support of an increased risk for heaviest cumulative use of mobile phones but less clear for latency. Thus, there are some similarities with our findings.

In conclusion, in the present study, no conclusive evidence of an association between use of mobile and cordless phones and meningioma was found. However, an increased risk was noted among heavy users of mobile and cordless phones, especially in the highest decile of cumulative use. The risk increased somewhat with latency, although the result was not statistically significant. Meningioma risk was not associated with tumor localization or ipsilateral use. However, taking the long latency periods that have been reported for the increased meningioma risk associated with exposure to ionizing radiation it remains too early to make a definitive risk assessment. Results for even longer latency periods of wireless phone use than in this study are desirable.