Mobile phone use and acoustic neuroma. Professor Maria Feychting Institute of Environmental Medicine

Transcription

1 Mobile phone use and acoustic neuroma Professor Maria Feychting Institute of Environmental Medicine

2 ? Cannot affect biologic materia at all Brain tumors Other cancer Headache Tiredness Vertigo Sense of heat Burnouts Asthma, allergy etc Mad cow disease Maria Feychting 29 marzo

3 Starting point for research Public concern about a new technology that has become widespread in a short period of time Not a biologically based hypothesis or seminal study Maria Feychting 29 marzo

4 How can we draw conclusions? One single study can never prove anything!! All studies have different types of bias, some more, other less You must assess results from all available studies The only criterion for exclusion of a study is poor quality All studies must be evaluated using the same standards, i.e. the same quality criteria regardless of the results Also studies that do not confirm your prior beliefs! You must weigh together comparable results You cannot pick arbitrary findings Maria Feychting 29 marzo

5 Cancer development - a multistage process Induktion period Latency period promotion progression initiation disease diagnosis Maria Feychting 29 marzo

6 Acoustic neuroma More correctly called vestibular schwannoma Benign tumor that arises on the eighth cranial nerve leading from the brain to the inner ear The incidence varies between 1 to 20 per million/year A pronounced increase in the incidence after introduction of CT (Computed Tomography) Some increase after introduction of MRI (Magnetic Resonance Imaging) Difficult to assess if a true increase has occurred many cases remain undetected Maria Feychting 29 marzo

7 Age specific AN incidence, Denmark Howitz et al Maria Feychting 29 marzo

8 Acoustic neuroma, cont. Early symptoms: Unilateral (one-sided) hearing loss Tinnitus Dizziness/loss of balance Grows slowly during a period of years before being diagnosed, about half of tumors do not grow further after detection Needs to be removed if it pressures on surrounding tissue Average time between first symptoms and diagnosis >5 years (Thomsen J, 1990) Maria Feychting 29 marzo

9 Potential sources of error in the epidemiological studies Difficult for cases and controls to remember mobile phone use years ago If misclassification the same for cases and controls more difficult to detect associations should they exist If cases tend to overreport mobile phone use association overestimated Selection bias among controls - nonparticipation If mobile phone users are more likely to participate association underestimated Short period of exposure in most studies Maria Feychting 29 marzo

10 Acoustic neuroma and mobile phone use Study RR (95% CI) No. exposed Exposure duration cases Hardell ( ) 5 Ever exposed Inskip ( ) 22 Regular use Johansen ( ) 7 Ever had mobile phone subscription Muscat ( ) 7 > 1 year Hardell ( ) 38 > 1 year ( Analogue) Christensen ( ) 45 Regular use Lönn ( ) 89 > 1 year r egular use Hardell (1.8-10) 2.0 ( ) > 1 year ( Analogue) > 1 year ( Digital ) Schoemaker ( ) 360 >1 year r egular use Takebayashi ( ) 51 >1 year regular use Schlehofer ( ) 29 >1 year regular use Maria Feychting 29 marzo

11 Hardell studies Exp cases RR (95 % CI) Comments Hardell ( ) >1 yrs Hardell ( ) >1 yrs; Analogue ( ) >1 yrs; Digital ( ) 1-5 yrs; Analogue ( ) >5-10 yrs; Analogue ( ) >10 yrs; Analogue Hardell (1.8-10) >1 yrs; Analogue ( ) >1 yrs; Digital (1.4-69) 1-5 yrs; Analogue (1.9-14) 2.6 ( ) >5-10 yrs; Analogue >10 yrs; Analogue ( ) 1-5 yrs; Digital ( ) >5-10 yrs; Digital Maria Feychting 29 marzo

12 But didn t the US studies find increased risks for long term use? Inskip 2001: OR 0.3 ( ) <0.5 years OR 1.8 ( ) 0.5-<3 years OR 1.4 ( ) >3 years OR 1.9 ( ) >5 years Muscat 2002: OR 0.5 ( ) 1-2 years OR 1.7 ( ) 3-6 years Maria Feychting 29 marzo

13 On the other hand.. Christensen 2004: OR 0.9 ( ) 1-4 years OR 0.9 ( ) 5-9 years OR 0.2 ( ) >10 years Schlehofer 2007: OR 0.8 ( ) 1-4 years OR 0.5 ( ) 5-9 years 0 cases, 3 controls >10 years Maria Feychting 29 marzo

14 Results from the larger studies No. exp cases RR (95 % CI) Time since first use Lönn ( ) 1-4 yrs ( ) ( ) 10 Schoemaker ( ) 0.9 ( ) yrs ( ) 10 Hardell (1.4-69) 1-5 yrs Analogue (1.9-14) ( ) > ( ) 1-5 yrs Digital ( ) ( ) >10 Maria Feychting 29 marzo

15 Acoustic neuroma - laterality Lönn 2004 Time since first use Ipsilateral* 3.9 ( ) 10 years Contralateral 0.8 ( ) Schoemaker 2005 Ipsilateral 1.3 ( ) 10 years Contralateral 1.0 ( ) (Ipsilateral 1.8 ( ) Duration of use) (Contralateral 0.9 ( ) Hardell 2005 Ipsilateral 5.1 ( ) Analogue >1 year Contralateral 4.9 (1.2-21) * Ipsilateral = tumor and mobile phone use on the same side of the head Maria Feychting 29 marzo

16 Potential bias in studies of acoustic neuroma Likely that tumor side affect cases report of side of mobile phone use Cases may tend to overreport use on the same side Cases who used the phone on the same side have changed side after the occurrence of the disease (hearing loss) Possible that exposure may influence detection of tumor Unilateral hearing loss discovered during mobile phone use Maria Feychting 29 marzo

17 Acoustic neuroma - conclusions Taken together, evidence support that short term mobile phone use (<10 years) do not affect risk For long term mobile phone use, the possibility of an increased risk cannot be excluded, additional data are needed Number of long term users are small in most studies Additional research is needed to evaluate long term use improved exposure assessment is essential Need to address problems with recall bias and nondifferental exposure misclassification Maria Feychting 29 marzo