Residential greenness and children working memory. An EU Child Cohort Network consortium study

Cognitive tasks such as language comprehension, learning, reasoning and problem-solving require the storage and management of information (Baddeley, 1992; Vuontela et al., 2003). One key executive function for these purposes is working memory (WM), which emerges from the interaction between memory and attention and allows an individual to store and manipulate information for short periods of time (Cowan, 2014; Shelton et al., 2010). Longitudinal studies on WM have shown that it improves during childhood before showing a period of latency in early adolescence (10–13 years; Ahmed et al., 2022; Reynolds et al., 2022). WM also shows a brief second period of improvement in middle adolescence (14–16 years).<br/><br/>Environmental epidemiologists and researchers in related disciplines have been working intensively during the past decade to map and quantify the potential salutogenic effects of green spaces and greenness on a wide range of health outcomes (Dzhambov et al., 2020; Markevych et al., 2017). One of the potential pathways for positive impact is the reduction of exposure to air pollutants because: (i) pollutants may become deposited on vegetated surfaces (Lindén et al., 2023); (ii) green spaces create an increased distance to emission sources such as roads (Klingberg et al., 2017). In this context, the study of whether higher exposure to residential green spaces and greenness leads to higher working memory scores has received considerable attention. A recently published systematic review (Buczyłowska et al., 2023) compiled the results of seven observational studies linking green space and greenness metrics with WM outcomes in participants of various ages between 4 and 18 years. Four of these studies showed statistically significant protective effects. The remaining three studies did not find any supporting evidence. In a more recent study, not included in that systematic review, marginally significant associations (p &lt; 0.10) were found between both green space availability and residential Normalized Difference Vegetation Index (NDVI) and WM scores and in a sample of over 1600 children aged 6–11 years living in various European cities (Fernandes et al., 2023).<br/><br/>In the present study, we wanted to contribute to the debate by analysing new data that could help clarify the associations, if any, between residential green spaces, greenness metricsand WM. In addition, we wished to explore the specific issue of reduced exposure to NO2, a pollutant that has been specifically linked to WM performance in childhood (Alemany et al., 2018; Forns et al., 2017; Sunyer et al., 2015).