Table 1

Synopsis of epidemiological studies attributed as “negative” with respect to a possible association between mobile phone use and cancer

Rothman et al (1996)Dreyer et al (1999)Muscat et al (2000)Inskip et al (2001)Johansen et al (2001)Muscat et al (2002)
*In addition to age and gender.
†Based on the assumption of a relative risk of 2.
TypeCohortCohort (extension of Rothman et al, 1996)Hospital based case-controlHospital based case-controlRetrospective cohortHospital based case-control
Endpoint(s)Overall mortalityBrain cancer, leukaemia, motor vehicle accidents, circulatory deathsPrimary brain cancerBrain tumours (primary brain cancer, meningioma, acoustic neurinoma)Cancer incidence. Brain and nervous system cancer, salivary gland cancer, leukaemia of a priori interestAcoustic neurinoma
No. cases/controls; size of cohorts59245 portable bag/car; 48932 hand-held; 147340 unknown phone type152138 portable bag/car; 133423 hand-held469 cases; 422 controls489 malignant; 293 benign tumours; 799 controls420095 subscribers (154 brain and nervous tumours, 84 cases of leukaemia)90 cases; 86 controls
Exposure assessmentCompany recordsCompany recordsInterviewInterviewCompany recordsInterview
Outcome assessmentSSA Death Master FileNational Death IndexPathology and MRIHistopathology, MRI/CTDanish Cancer RegistryPathology and MRI
Telephone type(s)AnalogueAnalogue88% analogueNot specified42% analogue; 58% digitalNot specified
Duration of follow up/duration of phone use1 year follow up; 1.8 y av. phone use1 year follow up; 1.9 y av. phone use2.8 y av. phone use, 14% users among cases, of these 74% less than 4 y18% regular users in cases, of these 84% less than 5 y1–14 y of follow up. Overall 92% less than 5 y, digital phones: 93% less than 3 y20% users in cases, of these 61% 3–6 y
Confounders considered*NoneMetropolitan areaYears of education, race, study centre, proxy interview, month and year of interviewEducation, income, date of interview, proxy interview, race, hospital, distance residence to hospitalNoneEducation, study centre, occupation, date of interview
FindingsNo difference in overall mortality between users of different types of telephonesIncreasing mortality from motor vehicle accident with increasing intensity of use. Higher mortality for brain tumours for longer duration of use (but only overall 2 deaths)Overall no increased OR. Highest OR for neuroepitheliomatous cancer (2.1). Tumours occurred more frequently at the side the telephone was used (p = 0.06)Overall no increased OR. No association with side of the head the phone was predominantly usedOverall cancer incidence reduced in men but not in women. Testicular cancer slightly increased (SIR 1.12). No overall increased brain tumour incidence. Highest SIRs for brain tumours and leukaemia for longest duration of useOverall no increased risk. OR = 1.7 for 3–6 y of use. Cases used a mobile phone on av. 4.1 y compared to 2.2 y in controls. Tendency for greater proportion of contralateral use (p = 0.07)
Evaluation
Selection of participantsOnly 33% of subscriber records selected, in only 14% type of telephone ascertainedSame as Rothman et al, 1996Hospital controls including cancer patients. Except first year only prevalent cases. Response rate: cases 82%, controls 90%Hospital controls. Response rate: cases 92%, controls 86%Only 58% of subscribers selectedHospital controls. Only prevalent cases. Response rate not specified
Power†80% for overall survivalNegligible for cancer causes of death88% overall. For >4 y of use and excluding glioblastoma (52%) power less than 20%99% overall. For >3 y use and excluding glioblastoma (49%) power less than 40%Overall brain tumours: 100%; leukaemia 100%. For ⩾3 use 62% for brain tumours, 39% for leukaemia50% overall. For >3 y 25%
Exposure assessmentNoneIntensity and duration of use only from company recordsInterviewer not blinded to case statusInterviewer not blinded to case statusNo data on intensity of use, duration of use only for digital phones from company recordsInterviewer not blinded to case status
Outcome assessmentNoneNoneHistopathology not unequivocal in all casesState of the artNoneState of the art
Confounding and biasMore than 70% of users excluded. Exposure misclassification. Assessment of laterality not possible. Healthy group effectSame as Rothman et al, 1996Cases interviewed within 48 h after surgery. Response and recall bias possibleMore proxy interviews in cases than controlsComparison to general population containing users and non-users. More than 42% of users excluded. Exposure misclassification. Assessment of laterality not possible. Healthy group effectIndication of reversal of cause and effect
Latency consideredNoNoNoNoNoNo
Statistical methodsStandardStandardStandard, laterality by χ2 testStandard, laterality by Fisher’s exact testStandardStandard, laterality by Fisher’s exact test