The RANCH project examined exposure-effect relationships between chronic aircraft noise exposure, chronic road traffic noise exposure and combinations of chronic aircraft and road traffic noise exposure and cognitive performance in 9-10 year old children living around major airports in the Netherlands, Spain, and the UK. Children were selected to participate on the basis of external noise exposure at school, which was predicted from noise contour maps, modelling and on-site measurements. Schools matched for socio-economic position within countries were selected. The same standardised paper and pen cognitive tests of episodic memory (recognition memory, conceptual recall and information recall), working memory, prospective memory and sustained attention were used in each country and nationally standardised reading comprehension tests were employed. Parents completed a questionnaire about the family's health and social background. A total of 2844 children from 89 schools around Schiphol Amsterdam, Barajas Madrid and London Heathrow airports participated in this study.
The data from the three countries was pooled and analysed using multilevel modelling. Analyses for aircraft noise exposure and road traffic noise exposure were conducted separately to examine single-exposure effects and were entered as a multiplicative interaction to examine combined-exposure effects. Analyses adjusted for age, gender, centre (NL, Spain or UK), mother's educational attainment, employment status, crowding, home ownership, long standing illness, main language spoken at home, parental support for school work and classroom glazing and the other noise exposure variable (e.g. for aircraft noise exposure analyses, road traffic noise exposure was also adjusted for).
Aircraft noise exposure was related to impaired performance in reading comprehension and recognition memory in all three countries. Reading age in children exposed to high levels of aircraft noise was delayed by up to 2 months in the UK and by up to 1 month in the Netherlands for a 5 dB change in noise exposure. The relationship between aircraft noise and reading comprehension and recognition memory was linear and could not be accounted for by sociodemographic variables or acute noise during testing.
Aircraft noise exposure was not associated with impairment of episodic memory - as measured by conceptual recall and information recall, working memory, prospective memory or sustained attention. Road traffic noise exposure was linearly associated with increased epidosic memory scores - as measured by conceptual recall and information recall but was not associated with reading comprehension, recognition memory, working memory, prospective memory or sustained attention. Combined noise exposure was related to reading comprehension; high levels of road traffic noise moderated the effect of high levels of aircraft noise on reading. There were no effects of combined exposure on either episodic memory, working memory, prospective memory or sustained attention.
In a sub-sample of 24 Dutch schools the impact of air and road traffic noise exposure was also investigated with the Neurobehavioural Evaluation System (NES), which is a computerised test battery. By means of the NES aspects of attention, psychomotor performance, perceptual coding and memory were measured. Significant associations were found between both aircraft noise exposure and road traffic noise exposure and the complex tasks of the switching attention test. No effects were found for aircraft noise exposure or road traffic noise exposure and motor functioning, perceptual coding or memory. Combined noise had a significant effect on simple reaction time and the attention test. Performance for reaction time and attention increased with increasing aircraft noise exposure in schools with low road traffic noise exposure and decreased with increasing aircraft noise exposure in schools with high road traffic noise exposure. In conclusion, the effects observed in the more complex tasks are in line with the finding that complex tasks are influenced by noise exposure.