Exploring blue spaces’ effects on childhood leukaemia inci-dence: A population-based case-control study in Spain

Abstract

Background and aim: Blue spaces have been a key part of human evolution, providing resources and helping economies develop. To date, no studies have been carried out to explore how they may be linked to paediatric oncological diseases. The aim of this study was to explore the possible relationship of residential proximity to natural and urban blue spaces on childhood leukaemia. Methods: A population-based case control study were conducted in four regions of Spain across the period 2000-2018. 936 incident cases and 5,616 controls were included, individually matched by sex, year-of-birth and place-of-residence. An exposure proxy with four distances (250m, 500m, 750m and 1 km) to blue spaces was built using the geographical coordinates of the participants’ home residences. Odds ratios (ORs) and 95% confidence intervals (95%CIs), blue space exposure were calculated for overall childhood leukaemia, and the acute lymphoblastic (ALL) and acute myeloblastic leukaemia (AML) subtypes, with adjustment for socio-demographic and environmental covariates. Results: A decrease in overall childhood leukaemia and ALL-subtype incidence was found as we came nearer to children’s places of residence, showing, for the study as a whole, a reduced incidence at 250m (odds ratio (OR)=0.77; 95%CI=0.60-0.97), 500m (OR=0.78; 95%CI=0.65-0.93), 750m (OR=0.80; 95%CI=0.69-0.93) and 1000m (OR=0.84; 95%CI=0.72-0.97). AML model results showed an increasing incidence at closest to subjects’ homes (OR at 250m = 1.06; 95%CI=0.63-1.71). Conclusions: Our results suggest a possible association between lower childhood-leukaemia incidence and blue-space proximity. This study is a first approach to blue spaces’ possible effects on childhood leukaemia incidence; consequently, it is necessary to continue studying these spaces – while taking into account more individualized data and other possible environmental risk factors. Keywords: urban blue spaces; environmental factors; childhood cancer; childhood leukaemia; incidence; spatial epidemiology.