Researchers have carried out several types of epidemiologic studies in humans to investigate the possibility of a relationship between cell phone use and the risk of malignant (cancerous) brain tumors, such as gliomas, as well as benign (noncancerous) tumors, such as acoustic neuroma (tumors in the cells of the nerve responsible for hearing that are also known as vestibular schwannomas), meningiomas (usually benign tumors in the membranes that cover and protect the brain and spinal cord), and parotid gland tumors (tumors in the salivary glands) (3).

In one type of study, called a case–control study, cell phone use is compared between people with these types of tumors and people without them. In another type of study, called a cohort study, a large group of people who do not have cancer at study entry is followed over time and the rate of these tumors in people who did and didn’t use cell phones is compared. Cancer incidence data can also be analyzed over time to see if the rates of brain tumors changed in large populations during the time that cell phone use increased dramatically. These studies have not shown clear evidence of a relationship between cell phone use and cancer. However, researchers have reported some statistically significant associations for certain subgroups of people.

Three large epidemiologic studies have examined the possible association between cell phone use and cancer: Interphone, a case–control study; the Danish Study, a cohort study; and the Million Women Study, another cohort study.

Interphone

How the study was done: This is the largest health-related case–control study of cell phone use and the risk of head and neck tumors. It was conducted by a consortium of researchers from 13 countries. The data came from questionnaires that were completed by study participants.

What the study showed: Most published analyses from this study have shown no statistically significant increases in brain or other central nervous system cancers related to higher amounts of cell phone use. One analysis showed a statistically significant, although modest, increase in the risk of glioma among the small proportion of study participants who spent the most total time on cell phone calls. However, the researchers considered this finding inconclusive because they felt that the amount of use reported by some respondents was unlikely and because the participants who reported lower levels of use appeared to have a slightly reduced risk of brain cancer compared with people who did not use cell phones regularly (4–6).

An analysis of data from all 13 countries participating in the Interphone study reported a statistically significant association between intracranial distribution of tumors within the brain and self-reported location of the phone (7). However, the authors of this study noted that it is not possible to draw firm conclusions about cause and effect based on their findings.

Additional analyses of data from Interphone countries

An analysis of data from five Northern European countries in the Interphone study showed an increased risk of acoustic neuroma only in those who had used a cell phone for 10 or more years (8).

In subsequent analyses of Interphone data, investigators addressed issues of risk according to specific location of the tumor and estimated exposures. One analysis of data from seven of the countries in the Interphone study found no relationship between brain tumor location and regions of the brain that were exposed to the highest level of radiofrequency radiation from cell phones (9). However, another study, using data from five of the countries, reported suggestions of an increased risk of glioma and, to a lesser extent, of meningioma developing in areas of the brain experiencing the highest exposure (10).

Danish Study

How the study was done: This cohort study, conducted in Denmark, linked billing information from more than 358,000 cell phone subscribers with brain tumor incidence data from the Danish Cancer Registry.

What the study showed: No association was observed between cell phone use and the incidence of glioma, meningioma, or acoustic neuroma, even among people who had been cell phone subscribers for 13 or more years (11–13).

Million Women Study

How the study was done: This prospective cohort study conducted in the United Kingdom used data obtained from questionnaires that were completed by study participants.

What the study showed: Self-reported cell phone use was not associated with an increased risk of glioma, meningioma, or non-central nervous system tumors. Although the original published findings reported an association with an increased risk of acoustic neuroma (14), this association disappeared after additional years of follow-up of the cohort (15).

In addition to these three large studies, other, smaller epidemiologic studies have looked for associations between cell phone use and cancer. These include:

Two NCI-sponsored case–control studies, each conducted in multiple U.S. academic medical centers or hospitals between 1994 and 1998 that used data from questionnaires (16) or computer-assisted personal interviews (17). Neither study showed a relationship between cell phone use and the risk of glioma, meningioma, or acoustic neuroma.

The CERENAT study, another case–control study conducted in multiple areas in France from 2004 to 2006 using data collected in face-to-face interviews using standardized questionnaires (18). This study found no association for either gliomas or meningiomas when comparing regular cell phone users with non-users. However, the heaviest users had significantly increased risks of both gliomas and meningiomas.

A pooled analysis of two case–control studies conducted in Sweden that reported statistically significant trends of increasing brain cancer risk for the total amount of cell phone use and the years of use among people who began using cell phones before age 20 (19).

Another case–control study in Sweden, part of the Interphone pooled studies, did not find an increased risk of brain cancer among long-term cell phone users between the ages of 20 and 69 (20).

The CEFALO study, an international case–control study of children diagnosed with brain cancer between ages 7 and 19, which found no relationship between their cell phone use and risk for brain cancer (21).

Investigators have also conducted analyses of incidence trends to determine whether the incidence of brain or other cancers has changed during the time that cell phone use increased dramatically. These include: