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Epidemiological Study (case-control study, pooled analysis)

Pooled analysis of two case-control studies on the use of cellular and cordless telephones and the risk of benign brain tumours diagnosed during 1997-2003. epidemiol.

By: Hardell L, Carlberg M, Hansson Mild K
Published in: Int J Oncol 2006; 28 (2): 509 - 518 ( open external web page PubMed Entry , open external web page Journal web site )

Aim of study (according to author)
A pooled analysis of two previous case-control studies on the use of cellular and cordless telephones and the risk of benign brain tumors was conducted in Sweden.
Background/further details:
The first case-control study regarding the period 1997-2000 was published in the publications 9105 and 9520. The second study regarding the period 2000-2003 was published in publication 12068 concerning benign brain tumors and in publication 12259 concerning malignant brain tumors.

Endpoint/type of risk estimation

Estimate of incidence by odds ratio (OR)

Exposure

groups of exposure:

Reference group 1:   unexposed  
group 2:  analog > 1- to 5-year latency period  
group 3:  analog > 5- to 10-year latency period 
group 4:  analog > 10-year latency period  
group 5:  analog > 15-year latency period  
group 6:  analog total, > 1-year latency period  
group 7:  analog ≤ 85 h, > 1- to 5-year latency period  
group 8:  analog ≤ 85 h, > 5- to 10-year latency period 
group 9:  analog ≤ 85 h, > 10-year latency period  
group 10:  analog ≤ 85 h, total, > 1-year latency period  
group 11:  analog > 85 h, > 1- to 5-year latency period  
group 12:  analog > 85 h, > 5- to 10-year latency period 
group 13:  analog > 85 h, > 10-year latency period  
group 14:  analog > 85 h, total, > 1-year latency period  
group 15:  digital > 1- to 5-year latency period  
group 16:  digital > 5- to 10-year latency period 
group 17:  digital > 10-year latency period  
group 18:  digital total, > 1-year latency period  
group 19:  digital ≤ 64 h, > 1- to 5-year latency period  
group 20:  digital ≤ 64 h, > 5- to 10-year latency period 
group 21:  digital ≤ 64 h, > 10-year latency period  
group 22:  digital ≤ 64 h, total, > 1-year latency period  
group 23:  digital > 64 h, > 1- to 5-year latency period  
group 24:  digital > 64 h, > 5- to 10-year latency period 
group 25:  digital > 64 h, > 10-year latency period  
group 26:  digital > 64 h, total, > 1-year latency period  
group 27:  cordless > 1- to 5-year latency period  
group 28:  cordless > 5- to 10-year latency period 
group 29:  cordless > 10-year latency period  
group 30:  cordless total, > 1-year latency period  
group 31:  cordless ≤ 195 h, > 1- to 5-year latency period  
group 32:  cordless ≤ 195 h, > 5- to 10-year latency period 
group 33:  cordless ≤ 195 h, > 10-year latency period  
group 34:  cordless ≤ 195 h, total, > 1-year latency period  
group 35:  cordless > 195 h, > 1- to 5-year latency period  
group 36:  cordless > 195 h, > 5- to 10-year latency period 
group 37:  cordless > 195 h, > 10-year latency period  
group 38:  cordless > 195 h, total, > 1-year latency period  

Population

  • case group
    men and women, aged from 20 to 80 years
    diagnosis: brain tumor, histopathologically verified
    observation period: January 1997 - December 2003
    study location: Sweden (Uppsala/Örebro and Linköping medical regions 1997-2003, Stockholm and Gothenburg regions 1997-2000)
    source of data: Cancer registry
    exclusion criteria: deceased, medical conditions

  • control group

    matching: sex, age, area
Further parameters acquired by questionnaire (working history, exposure to different agents, smoking habits)

Study size i cases  controls 
number eligible 1,4292,437
number participating 1,2542162
rate of participating 88%89%

Other: benign and malignant brain tumors total: 2437, controls for malignant and benign cases

Statistically significant results i

 group  exposure  endpoint  cases  controls  parameter (OR confidence interval 
5analog > 15-year latency period acoustic neuroma6223.81.4-10
6analog total, > 1-year latency period acoustic neuroma682972.92.0-4.3
18digital total, > 1-year latency period acoustic neuroma1057751.51.1-2.1
30cordless total, > 1-year latency period acoustic neuroma967011.51.04-2.0

Statistical analysis using unconditional logistic regression (adjusted for age, 5-year age group, socioeconomic status, year of diagnosis)

Results/conclusion (according to author)
The results showed an increased risk of benign brain tumors, especially acoustic neuroma. The highest risk for acoustic neuroma was found for a latency period of more than 15 years for use of analog cellular phones. No convincing pattern of association was observed for other types of benign brain tumors.

Limitations (according to author): Several calculations were based on low numbers.

(Study character: epidemiological study, case-control study, pooled analysis)

Study funded by

  • Cancer och Allergifonden (Cancer and Allergy Foundation), Sweden
  • Cancerhjälpen (Cancerhelp), Sweden
  • Nyckelfonden, Sweden
  • Örebro Cancer Fund, Sweden

Published comment on this article:Related articles i
Glossary: acoustic neuroma, analog, antenna, benign, brain tumors, cancer registry, case-control study, cellular, cellular phones, confidence interval, cordless phone, diagnosis, digital, ear, endpoint, epidemiological, exposure, histopathologically, incidence, latency, malignant, matching, mean, meningioma, mobile communication, OR, pooled analysis, questionnaire, risk, socioeconomic status, statistical, unconditional logistic regression
Exposure: mobile communication system, analog mobile phone, digital mobile phone, cordless phone, personal exposure

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