The association between the mobile phone use and risk of brain tumors was investigated in a meta-analysis. Furthermore the aim was to investigate whether methodological quality of studies and source of funding can explain the variation in results.
Following 22 studies were included: Hardell et al. 1999, Muscat et al. 2000, Inskip et al. 2001, Auvinen et al. 2002, Hardell et al. 2002, Warren et al. 2003, Hardell et al. 2005, Lönn et al. 2005, Schoemaker et al. 2005, Hardell et al. 2006, Schüz et al. 2006, Takebayashi et al. 2006, Hours et al. 2007, Lahkola et al. 2007, Schlehofer et al. 1990, Lahkola et al. 2008, Takebayashi et al. 2008, Hardell et al. 2010, INTERPHONE Study Group 2010 , INTERPHONE Study Group 2011, Aydin et al. 2011, and Coureau et al. 2015.
The quality of studies was assessed using the modified Newcastle–Ottawa Quality Assessment Scale. The source of funding of the studies were categorized into government funding, industrial funding and mixed (e.g. Interphone project) funding.
Analysis of 14 case-control studies showed practically no increase in risk of brain tumor associated with mobile phone use (OR 1.03, CI 0.92–1.14). However, in a subgroup with mobile phone use of 10 years or longer (or > 1640 h), the result of the meta-analysis of 7 studies showed a significant increase in risk (OR 1.33, CI 1.07-1.66).
Analysis according to the tumor type showed a non-significant increased risk for glioma (OR 1.08, CI 0.94–1.25), a decreased risk for meningioma (OR 0.84, CI 0.75-0.93) and a non-significant increased risk for acoustic neuroma (OR 1.04, CI 0.82–1.33).
Government funded as well as phone industry funded studies showed a non-significant increased risk of brain tumor (OR 1.07, CI 0.92-1.24; OR 1.07, CI 0.68-1.69, respectively), while mixed funded studies showed a decreased risk (OR 0.90, CI 0.84-0.97).
A significantly positive correlation was observed between study quality (scores between 5 and 8) and risk of brain tumor associated with mobile phone use. Higher quality studies show a statistically significant association between mobile phone use and risk of brain tumor. Even the source of funding was found to affect the quality of results produced by the studies.
The authors concluded that they found evidence linking mobile phone use and risk of brain tumors especially in long-term users (≥ 10 years). Studies with higher quality showed a trend towards high risk of brain tumor, while lower quality showed a trend towards lower risk or protection.