Epidemiological study (observational study)

A case-case study of mobile phone use and acoustic neuroma risk in Japan epidem.

By: Sato Y, Akiba S, Kubo O, Yamaguchi N

Published in: Bioelectromagnetics 2011; 32 (2): 85-93

Aim of study (acc. to author)

A case-case study was conducted in Japan to investigate the association between mobile phone use and the risk of acoustic neuroma.

Further details

Only persons with an acoustic neuroma are included in this case-case study, the affected ear is regarded as the case side, while the opposite ear is regarded as the control side.
Mobile phone use before the two reference dates (1 and 5 years before diagnosis) was analyzed. Regular mobile phone use was defined as using a mobile phone at least once a week for 6 months or longer.

Endpoint/type of risk estimation

brain tumor: acoustic neuroma

Type of risk estimation:

incidence

(relative risk (RR))

Exposure

- mobile communications
- mobile phone
- personal

Assessment

questionnaire: past history of mobile phone use, year of starting mobile phone use, average daily number of outgoing and incoming calls, average call duration, proportion of calls using the left and right ears, and use of hands-free devices
calculation: average daily call duration calculated by multiplying the average number of calls/day by the average duration of one call; weighted average number of calls per day, weighted average duration of one call, and weighted average daily call duration weighted by the proportion of calls made using each ear

Exposure groups

Group	Description
Group 1	mobile phone use 1 year before diagnosis; years since start of mobile phone use: ≤ 5
Group 2	mobile phone use 1 year before diagnosis; years since start of mobile phone use: 5-10
Group 3	mobile phone use 1 year before diagnosis; years since start of mobile phone use: >10
Group 4	mobile phone use 1 year before diagnosis; weighted average number of calls/day: ≤ 1
Group 5	mobile phone use 1 year before diagnosis; weighted average number of calls/day: 1-3
Group 6	mobile phone use 1 year before diagnosis; weighted average number of calls/day: 3-5
Group 7	mobile phone use 1 year before diagnosis; weighted average number of calls/day: > 5
Group 8	mobile phone use 1 year before diagnosis; weighted average duration of one call: ≤ 1 min
Group 9	mobile phone use 1 year before diagnosis; weighted average duration of one call: 1-3 min
Group 10	mobile phone use 1 year before diagnosis; weighted average duration of one call: 3-5 min
Group 11	mobile phone use 1 year before diagnosis; weighted average duration of one call: > 5 min
Group 12	mobile phone use 1 year before diagnosis; weighted average daily call duration: ≤ 3 min
Group 13	mobile phone use 1 year before diagnosis; weighted average daily call duration: 3-10 min
Group 14	mobile phone use 1 year before diagnosis; weighted average daily call duration: 10-20 min
Group 15	mobile phone use 1 year before diagnosis; weighted average daily call duration: > 20 min
Group 16	mobile phone use 5 year before diagnosis; years since start of mobile phone use: ≤ 5
Group 17	mobile phone use 5 year before diagnosis; years since start of mobile phone use: 5-10
Group 18	mobile phone use 5 year before diagnosis; years since start of mobile phone use: >10
Group 19	mobile phone use 5 year before diagnosis; weighted average number of calls/day: ≤ 1
Group 20	mobile phone use 5 year before diagnosis; weighted average number of calls/day: 1-3
Group 21	mobile phone use 5 year before diagnosis; weighted average number of calls/day: 3-5
Group 22	mobile phone use 5 year before diagnosis; weighted average number of calls/day: > 5
Group 23	mobile phone use 5 year before diagnosis; weighted average duration of one call: ≤ 1 min
Group 24	mobile phone use 5 year before diagnosis; weighted average duration of one call: 1-3 min
Group 25	mobile phone use 5 year before diagnosis; weighted average duration of one call: 3-5 min
Group 26	mobile phone use 5 year before diagnosis; weighted average duration of one call: > 5 min
Group 27	mobile phone use 5 year before diagnosis; weighted average daily call duration: > 5 min
Group 28	mobile phone use 5 year before diagnosis; weighted average daily call duration: ≤ 3 min
Group 29	mobile phone use 5 year before diagnosis; weighted average daily call duration: 3-10 min
Group 30	mobile phone use 5 year before diagnosis; weighted average daily call duration: 10-20 min

Population

Group:
- men
- women
Age: ≥ 20 years
Characteristics: acoustic neuroma
Observation period: January 2000 - December 2006
Study location: Japan
Data source: 22 hospitals with neurosurgery departments in Japan

Study size

Type	Value
Eligible	1,589
Participants	804
Evaluable	787

Results (acc. to author)

Overall, no statistically significant increased risk of acoustic neuroma was identified for regular mobile phone use compared to non-use, with risks of 1.08 (CI 0.93-1.28) for use until 1 year before diagnosis and 1.14 (CI 0.96-1.40) for use until 5 years before diagnosis. A significantly increased risk was observed in cases who reported having used mobile phones on the affected ear for >20 min/day on average (RR 2.74 at 1 year before diagnosis (CI 1.18-7.85) and RR 3.08 at 5 years before diagnosis (CI 1.47-7.41)). Cases with ipsilateral combination of tumor location and more frequently used ear were found to have tumors with smaller diameters, suggesting an effect of detection bias. Furthermore, analysis of the distribution of left and right tumors suggested an effect of tumor-side-related recall bias for recall of mobile phone use at 5 years before diagnosis.
The increased risk identified for mobile phone users with average call duration >20 min/day should be interpreted with caution, taking into account the possibilities of detection bias and recall bias. However, the authors could not conclude that the increased risk was entirely explicable by these biases, leaving open the possibility that mobile phone use increased the risk of acoustic neuroma.

Study funded by

Ministry of Internal Affairs and Communications, Japan

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