Abstract
BackgroundIncreased brain tumour incidence over recent decades may reflect improved diagnostic methods and clinical practice, but remain unexplained. Although estimated doses are low a relationship between radon and brain tumours may exist.ObjectiveTo investigate the long-term effect of exposure to residential radon on the risk of primary brain tumour in a prospective Danish cohort.MethodsDuring 1993–1997 we recruited 57,053 persons. We followed each cohort member for cancer occurrence from enrolment until 31 December 2009, identifying 121 primary brain tumour cases. We traced residential addresses from 1 January 1971 until 31 December 2009 and calculated radon concentrations at each address using information from central databases regarding geology and house construction. Cox proportional hazards models were used to estimate incidence rate-ratios (IRR) and 95% confidence intervals (CI) for the risk of primary brain tumours associated with residential radon exposure with adjustment for age, sex, occupation, fruit and vegetable consumption and traffic-related air pollution. Effect modification by air pollution was assessed.ResultsMedian estimated radon was 40.5 Bq/m3. The adjusted IRR for primary brain tumour associated with each 100 Bq/m3 increment in average residential radon levels was 1.96 (95% CI: 1.07; 3.58) and this was exposure-dependently higher over the four radon exposure quartiles. This association was not modified by air pollution.ConclusionsWe found significant associations and exposure-response patterns between long-term residential radon exposure radon in a general population and risk of primary brain tumours, adding new knowledge to this field. This finding could be chance and needs to be challenged in future studies.
Highlights
Brain tumours are rare; incidence rates in Nordic countries have increased during the past few decades in both men and women [1,2]
We found significant associations and exposure-response patterns between long-term residential radon exposure radon in a general population and risk of primary brain tumours, adding new knowledge to this field
We identified 121 primary brain tumour cases, corresponding to an overall incidence rate of 18.6 per 100,000 person-years
Summary
Brain tumours are rare; incidence rates in Nordic countries have increased during the past few decades in both men and women [1,2]. Epidemiological studies have investigated many potential risk factors for brain tumour over the past several decades, but the only established cause is ionizing radiation given in therapeutic [4,5,6,7] and diagnostic doses [8] and data from atomic bomb survivors support this [9,10]. A more recent study of uranium miners including 14 deaths due to brain tumours found an excess risk associated with radon exposure with no dose-response relationship and expressing caution of possible diagnostic misclassification [17]. No study to date has investigated the association between incidence of brain tumour and exposure to residential radon in the general population. Increased brain tumour incidence over recent decades may reflect improved diagnostic methods and clinical practice, but remain unexplained. Estimated doses are low a relationship between radon and brain tumours may exist
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