Brain tumors in children and adolescents and exposure to animals and farm life: a multicenter case-control study (CEFALO).
OBJECTIVE
The etiology of brain tumors in children and adolescents is largely unknown, and very few environmental risk factors have been identified. The aim of this study was to examine the relationship between pre- or postnatal animal contacts or farm exposures and the risk of childhood brain tumors (CBTs), since infectious agents may pose a risk factor and a proposed mechanism is transferral of infectious agents from animals to humans.


METHODS
The case-control study conducted in Denmark, Norway, Sweden, and Switzerland included brain tumor cases diagnosed from 2004 to 2008 aged 7-19 years at diagnosis. Three hundred and fifty-two cases (83 % participation rate) were matched to 646 population-based controls (71 % participation rate). Conditional logistic regression was used to estimate odds ratios.


RESULTS
Maternal farm residence during pregnancy was inversely related to all CBTs combined (adjusted odds ratio (aOR) = 0.40, 95 % confidence interval (CI) = 0.19-0.88), as was the child's farm residence but not statistically significantly so (aOR = 0.57, 95 % CI = 0.28-1.17). Exposure to animals was in general not related to CBT risk except postnatal contact with birds showing reduced aORs of all CBTs (0.67, 95 % CI = 0.46-0.97) and primitive neuroectodermal tumor (0.28, 95 % CI = 0.10-0.83). Sensitivity analyses focusing on early exposure of the child did not change the associations observed for the entire exposure period with the exception of exposure to goats and sheep which was associated with reduced risks of both all CBTs (aOR = 0.48, 95 % CI = 0.24-0.97) and astrocytomas (aOR = 0.29, 95 % CI = 0.10-0.87).


CONCLUSIONS
Altogether, our data indicate an inverse association between the mother during pregnancy or the child living on a farm and CBT risk, which contrasts with the existing literature and merits further attention. With respect to exposure to animals, we did not observe any systematic pattern. This suggests that a potential protective effect of farm residence is mediated by some other factor than animal contact.
Danish Cancer Society Research Center, Copenhagen, Denmark.
Jeppe Schultz
JS
Christensen
Laust Hvas
LH
Mortensen
Martin
M
Röösli
Maria
M
Feychting
Tore
T
Tynes
Tina Veje
TV
Andersen
Lisbeth Samsø
LS
Schmidt
Aslak Harbo
AH
Poulsen
Denis
D
Aydin
Claudia E
CE
Kuehni
Michaela
M
Prochazka
Birgitta
B
Lannering
Lars
L
Klaeboe
Tone
T
Eggen
Joachim
J
Schüz
D000293:Adolescent; D000383:Agriculture / Q000706:statistics & numerical data*; D000818:Animals; D001932:Brain Neoplasms / Q000453:epidemiology* / Q000209:etiology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012307:Risk Factors; D012537:Scandinavian and Nordic Countries / Q000453:epidemiology; D013557:Switzerland / Q000453:epidemiology; D055815:Young Adult