A large global study into a possible link between use of mobile phones and certain types of brain cancer has come to an inconclusive end and called for further research to be carried out.
The Interphone Study Group has published its results in the International Journal of Epidemiology, looking at the analyses of brain tumour (glioma and meningioma) risk in relation to mobile phone use.
Mobile phone use has increased dramatically since its introduction in the early-to-mid 1980’s, prompting concerns about health.
The International Agency for Research on Cancer (IARC) carried out an interview-based case-control study, which included 2,708 glioma and 2,409 meningioma cases and matched controls, conducted in 13 countries including the UK.
Interphone was the largest case-control study of mobile phone use and brain tumours yet and included the largest numbers of users with at least 10 years of exposure.
The 20m euro (£17m) Interphone study, backed by some funding from the mobile phone industry, involved interviewing 12,848 participants, of which 5,150 had been diagnosed with one of two types of brain cancer - glioma and meningioma - between 2000 and 2004.
These cancers were thought to be among the most likely to be influenced by phone use.
People were asked to record their mobile phone usage and the results were compared with adults of similar age, sex and background who did not have the disease.
The results showed up to 40% higher incidence of glioma among the top 10% of people who used their mobile phone most and 15% higher incidence of meningioma in that same group.
The authors, however, said this finding was questionable because of possible participation bias or other methodological limitations. No elevated risk for glioma or meningioma was observed after 10 years from first phone use.
They said: “Biases and errors limit the strength of the conclusions that can be drawn from these analyses and prevent a causal interpretation.”
Most participants were not heavy mobile phone users by today's standards, they added, and today’s mobile phone use has become much more prevalent as it is not unusual for young people to use mobile phones for an hour or more a day.
This increasing use was tempered, however, by the lower emissions, on average, from newer technology phones, and the increasing use of texting and hands-free operations that keep the phone away from the head.
Dr Christopher Wild, IARC director, said: "An increased risk of brain cancer is not established from the data from Interphone.
“However, observations at the highest level of cumulative call time and the changing patterns of mobile phone use since the period studied by Interphone, particularly in young people, mean that further investigation of mobile phone use and brain cancer risk is merited."