Temporal trends and geographical variability of the prevalence and incidence of attention deficit/hyperactivity disorder diagnoses among children in Catalonia, Spain.

Attention deficit/hyperactivity disorder (ADHD) is one of the most common behavioral disorders in childhood. According to a recent systematic review, the worldwide estimate of ADHD prevalence is 7.2% in children. This study aims to assess the prevalence of ADHD diagnoses in 2017 and the incidence of ADHD diagnoses in 2009-2017 in children living in Catalonia, Spain, as well as their temporal and geographical variability, and stratifying by sex and age. We used administrative data for all children aged 4 to 17 years who were insured in the public Catalan Health System in 2009-2017. We identified all ADHD cases diagnosed in 2009-2017 (ICD-9 code 314). We estimated the prevalence of ADHD diagnoses in 2017 and the overall annual incidence of ADHD diagnoses in 2009-2017. We used Poisson regression models to assess temporal trends in the incidence. We estimated a prevalence of ADHD diagnoses of 4.06% (95%CI 4.03, 4.10) in 2017, being 5.81% (95%CI 5.75, 5.87) for boys and 2.20% (95%CI 2.16, 2.24) for girls, the highest prevalence being in 13-to-17-year-olds (7.28% (95%CI 7.20, 7.36)). We did not observe a statistically significant increase of the incidence of ADHD diagnoses during the study period. Geographical differences were found across the healthcare areas in both prevalence and annual incidence and constant during the study period. In conclusion, the prevalence of ADHD diagnoses observed in this study was 4.06%, which was lower than the estimates reported in previous systematic reviews, but in line with the prevalence estimates from other recent European studies. The prevalence was higher in boys than girls, with a sex ratio consistent with previous studies. We did not observe an increase in the temporal trend of incidence of ADHD diagnoses in recent years, but we found geographical differences.

Association between Early Life Exposure to Air Pollution and Working Memory and Attention.

BACKGROUND: Although previous studies have reported negative associations between exposure to air pollution and cognition, studies of the effects of prenatal and postnatal exposures in early childhood have been limited. OBJECTIVES: We sought to assess the role exposure to fine particulate matter ([Formula: see text]) during different prenatal and postnatal windows may play in children's cognitive development at school age. METHODS: Within the Brain Development and Air Pollution Ultrafine Particles in School Children (BREATHE) Project, we estimated residential [Formula: see text] exposures by land use regression for the prenatal period and first seven postnatal years of 2,221 children from Barcelona, Spain. The participants ([Formula: see text]) completed computerized tests assessing working memory, attentiveness, and conflict network during four visits in 2012­2013. We used linear mixed effects and distributed lag models to assess the period of exposure to [Formula: see text] in association with cognitive development. RESULTS: Inverse associations were identified between [Formula: see text] exposure during the fifth and sixth postnatal years and working memory, with boys showing much higher vulnerability. Regarding attention functions, exposure to higher [Formula: see text] levels during the prenatal period and from the fourth postnatal year were associated with a reduction in conflict network performance, though we found no association with attentiveness. The overall estimated cumulative effect of a [Formula: see text] increase in [Formula: see text] resulted in a reduction in the working memory [Formula: see text] score of [Formula: see text] [95% confidence interval (CI): [Formula: see text], [Formula: see text]] points and an increase in the conflict attentional network of 11.31 (95% CI: 6.05, 16.57) milliseconds, indicating a poorer performance. CONCLUSIONS: Early life exposure to [Formula: see text] was associated with a reduction in fundamental cognitive abilities, including working memory and conflict attentional network. https://doi.org/10.1289/EHP3169.

Impact of commuting exposure to traffic-related air pollution on cognitive development in children walking to school.

A few studies have found associations between the exposure to traffic-related air pollution at school and/or home and cognitive development. The impact on cognitive development of the exposure to air pollutants during commuting has not been explored. We aimed to assess the role of the exposure to traffic-related air pollutants during walking commute to school on cognitive development of children. We performed a longitudinal study of children (n = 1,234, aged 7-10 y) from 39 schools in Barcelona (Catalonia, Spain) who commuted by foot to school. Children were tested four times during a 12-month follow-up to characterize their developmental trajectories of working memory (d' of the three-back numbers test) and inattentiveness (hit reaction time standard error of the Attention Network Test). Average particulate matter ≤2.5 µm (PM2.5), Black Carbon (BC) and NO2 concentrations were estimated using Land Use Regression for the shortest walking route to school. Differences in cognitive growth were evaluated by linear mixed effects models with age-by-pollutant interaction terms. Exposure to PM2.5 and BC from the commutes by foot was associated with a reduction in the growth of working memory (an interquartile range increase in PM2.5 and BC concentrations decreased the annual growth of working memory by 5.4 (95% CI [-10.2, -0.6]) and 4.6 (95% CI [-9.0, -0.1]) points, respectively). The findings for NO2 were not conclusive and none of the pollutants were associated with inattentiveness. Efforts should be made to implement pedestrian school pathways through low traffic streets in order to increase security and minimize children's exposure to air pollutants.

A Longitudinal Study on Attention Development in Primary School Children with and without Teacher-Reported Symptoms of ADHD.

Background: Prospective longitudinal studies are essential in characterizing cognitive trajectories, yet few of them have been reported on the development of attention processes in children. We aimed to explore attention development in normal children and children with attention deficit and hyperactivity disorder (ADHD) symptoms in a repeated measures design using the attention network test (ANT). Methods: The population sample included 2,835 children (49.6% girls) aged 7-11 years from 39 schools in Barcelona (Catalonia, Spain) who performed the ANT four times from January 2012 to March 2013. According to teacher ratings, 10.5% of the children presented ADHD symptoms. We performed multilevel mixed-effects linear regression models, adjusting for school and individual, to test the effects of age-related growth on the ANT networks: alerting, orienting and executive attention, and three measurements related to attentiveness: median of hit reaction time (HRT), hit reaction time standard error (HRT-SE) and variability. Results: We observed age-related growth in all the outcomes, except orienting. The curves were steeper at the younger groups, although for alertness the improvement was further at the oldest ages. Gender and ADHD symptoms interacted with age in executive attention, HRT and variability. Girls performed better in executive attention at young ages although boys reached females at around 10 years of age. For HRT, males showed faster HRT. However, girls had a more pronounced improvement and reached the levels of boys at age 11. Children with ADHD symptoms had significant differences in executive attention, HRT and variability compared to children without ADHD symptoms. Conclusions: We detected an ongoing development of some aspects of attention in primary school children, differentiating patterns by gender and ADHD symptoms. Our findings support the ANT for assessing attention processes in children in large epidemiological studies.

Traffic-related Air Pollution and Attention in Primary School Children: Short-term Association.

BACKGROUND: Although air pollution's short-term effects are well understood to be marked and preventable, its acute neuropsychological effects have, to our knowledge, not yet been studied. We aim to examine the association between daily variation in traffic-related air pollution and attention. METHODS: We conducted a follow-up study from January 2012 to March 2013 in 2,687 school children from 265 classrooms in 39 schools in Barcelona (Catalonia, Spain). We assessed four domains of children's attention processes every 3 months over four repeated visits providing a total of 10,002 computerized tests on 177 different days using the child Attention Network test (ANT). Ambient daily levels of nitrogen dioxide (NO2) and elemental carbon (EC) in particulate matter <2.5 µm (PM2.5) filters were measured at a fixed air quality background monitoring station and in schools. RESULTS: Daily ambient levels of both NO2 and EC were negatively associated with all attention processes (e.g., children in the bottom quartile of daily exposure to ambient NO2 levels had a 14.8 msecond [95% confidence interval, 11.2, 18.4] faster response time than those in the top quartile, which was equivalent to a 1.1-month [0.84, 1.37] retardation in the natural developmental improvement in response speed with age). Similar findings were observed after adjusting for the average indoor (classroom) levels of pollutants. Associations for EC were similar to those for NO2 and robust to several sensitivity analyses. CONCLUSIONS: The short-term association of traffic-related air pollutants with fluctuations in attention adds to the evidence that air pollution may have potential harmful effects on neurodevelopment. See video abstract at, http://links.lww.com/EDE/B158.

A Genome-Wide Association Study of Attention Function in a Population-Based Sample of Children.

BACKGROUND: Attention function filters and selects behaviorally relevant information. This capacity is impaired in some psychiatric disorders and has been proposed as an endophenotype for Attention-Deficit/Hyperactivity Disorder; however, its genetic basis remains largely unknown. This study aimed to identify single nucleotide polymorphism (SNPs) associated with attention function. MATERIALS AND METHODS: The discovery sample included 1655 children (7-12 years) and the replication sample included 546 children (5-8 years). Five attention outcomes were assessed using the computerized Attentional Network Test (ANT): alerting, orienting, executive attention, Hit Reaction time (HRT) and the standard error of HRT (HRTSE). A Genome-wide Association Study was conducted for each outcome. Gene set enrichment analyses were performed to detect biological pathways associated with attention outcomes. Additional neuroimaging analyses were conducted to test neural effects of detected SNPs of interest. RESULTS: Thirteen loci showed suggestive evidence of association with attention function (P<10-5) in the discovery sample. One of them, the rs4321351 located in the PID1 gene, was nominally significant in the replication sample although it did not survive multiple testing correction. Neuroimaging analysis revealed a significant association between this SNP and brain structure and function involving the frontal-basal ganglia circuits. The mTOR signaling and Alzheimer disease-amyloid secretase pathways were significantly enriched for alerting, orienting and HRT respectively (FDR<5%). CONCLUSION: These results suggest for the first time the involvement of the PID1 gene, mTOR signaling and Alzheimer disease-amyloid secretase pathways, in attention function during childhood. These genes and pathways have been proposed to play a role in neuronal plasticity, memory and neurodegenerative disease.

Developmental Trajectories in Primary Schoolchildren Using n-Back Task.

BACKGROUND: Neuropsychological instruments to assess cognitive trajectories during childhood in epidemiological studies are needed. This would improve neurodevelopment characterization in order to identify its potential determinants. We aimed to study whether repeated measures of n-back, a working memory task, detect developmental trajectories in schoolchildren during a 1-year follow-up. METHODS: We administered the n-back task to 2897 healthy children aged 7-11 years old from 39 schools in Barcelona (Spain). The task consisted of 2 levels of complexity or loads (2- and 3-back) and 2 different stimuli (numbers and words). Participants performed the task four times from January 2012 to March 2013. To study the trajectories during the follow-up, we performed linear mixed-effects models including school, individual and age as random effects. RESULTS: We observed improvements related to age in n-back outcomes d', HRT and accuracy, as well as reduced cognitive growth at older ages in d' and HRT. Greater improvements in performance were observed at younger ages, in 2-back, in verbal rather than numerical stimuli and in girls compared to boys. Boys responded faster at baseline, while girls showed increased growth in 2-back numbers. Children with ADHD (Attention Deficit and Hyperactivity Disorder) symptoms (15% of boys and 6% of girls) had a lower working memory at baseline, but they showed similar cognitive growth trajectories in numbers variants of the task, as compared to children without ADHD symptoms. However, the age-related improvement in response speed was not observed in children with ADHD symptoms. CONCLUSIONS: Changes in n-back outcomes reflected developmental trajectories in 1-year follow-up. The present results suggest that the repeated administration of this task can be used to study the factors that may alter the cognitive development during childhood.

Physical Activity and Cognitive Trajectories in Schoolchildren.

PURPOSE: The evidence regarding the role of physical activity (PA) habits on cognitive development in children is still scarce. Our study aimed to assess the association between PA habits and cognitive growth patterns, including working memory (WM) and inattentiveness in a large sample of primary schoolchildren. METHOD: This study included 2,897 children between 7 and 10 years old. WM was measured using the n-back task (2- and 3-back) and inattentiveness was measured using the attentional network task (ANT) on four occasions during one year. Parents completed a questionnaire with data about the extracurricular exercise of their child, commuting to school and other sociodemographic information at the first visit. RESULTS: Exercising twice per week or more was associated with better 2-back, 3-back and inattentiveness scores at baseline, as compared with the once per week or less category. Active commuting for more than 50 min was associated with better 3-back scores at baseline, as compared with passive commuting. No consistent associations were found between PA and cognitive growth. CONCLUSION: Overall, although children with high levels of PA performed better in cognitive tasks at baseline, PA levels had no clear effects on cognitive growth trajectories.

Traffic-Related Air Pollution, Noise at School, and Behavioral Problems in Barcelona Schoolchildren: A Cross-Sectional Study.

BACKGROUND: The available evidence of the effects of air pollution and noise on behavioral development is limited, and it overlooks exposure at schools, where children spend a considerable amount of time. OBJECTIVE: We aimed to investigate the associations of exposure to traffic-related air pollutants (TRAPs) and noise at school on behavioral development of schoolchildren. METHODS: We evaluated children 7-11 years of age in Barcelona (Catalonia, Spain) during 2012-2013 within the BREATHE project. Indoor and outdoor concentrations of elemental carbon (EC), black carbon (BC), and nitrogen dioxide (NO2) were measured at schools in two separate 1-week campaigns. In one campaign we also measured noise levels inside classrooms. Parents filled out the strengths and difficulties questionnaire (SDQ) to assess child behavioral development, while teachers completed the attention deficit/hyperactivity disorder criteria of the DSM-IV (ADHD-DSM-IV) list to assess specific ADHD symptomatology. Negative binomial mixed-effects models were used to estimate associations between the exposures and behavioral development scores. RESULTS: Interquartile range (IQR) increases in indoor and outdoor EC, BC, and NO2 concentrations were positively associated with SDQ total difficulties scores (suggesting more frequent behavioral problems) in adjusted multivariate models, whereas noise was significantly associated with ADHD-DSM-IV scores. CONCLUSION: In our study population of 7- to 11-year-old children residing in Barcelona, exposure to TRAPs at school was associated with increased behavioral problems in schoolchildren. Noise exposure at school was associated with more ADHD symptoms. CITATION: Forns J, Dadvand P, Foraster M, Alvarez-Pedrerol M, Rivas I, López-Vicente M, Suades-Gonzalez E, Garcia-Esteban R, Esnaola M, Cirach M, Grellier J, Basagaña X, Querol X, Guxens M, Nieuwenhuijsen MJ, Sunyer J. 2016. Traffic-related air pollution, noise at school, and behavioral problems in Barcelona schoolchildren: a cross-sectional study. Environ Health Perspect 124:529-535; http://dx.doi.org/10.1289/ehp.1409449.

Air Pollution and Neuropsychological Development: A Review of the Latest Evidence.

For the last decade, literature on the detrimental impacts of air pollution on brain, cognition and behavior has exponentially increased. Our aim is to review the latest epidemiologic literature on the association between outdoor air pollution and neuropsychological developmental in children. Two independent researchers searched for published studies between January 1, 2012 and June 12, 2015 in MEDLINE, Web of Science, and Science direct using defined keywords on outdoor air pollution and neuropsychological development. Selection of articles was based on study eligibility criteria. We encountered sufficient evidence of detrimental effects of pre- or postnatal exposure to polycyclic aromatic hydrocarbons on global intelligence quotient. The evidence was also sufficient for the association between pre- or postnatal exposure to fine particulate matter (PM2.5) and autism spectrum disorder, and limited evidence was encountered between nitrogen oxides and autism spectrum disorder. For other exposure-outcome associations reviewed, the evidence was inadequate or insufficient. Although evidence is not yet conclusive and further research is needed, the latest epidemiological studies support the hypothesis that pre- or postnatal exposure to ambient pollution, particularly polycyclic aromatic hydrocarbons, PM2.5, and nitrogen oxides has a negative impact on the neuropsychological development of children. The public health impact of air pollutants cannot be ignored and the precautionary principle should be applied to protect children.

Association between traffic-related air pollution in schools and cognitive development in primary school children: a prospective cohort study.

BACKGROUND: Air pollution is a suspected developmental neurotoxicant. Many schools are located in close proximity to busy roads, and traffic air pollution peaks when children are at school. We aimed to assess whether exposure of children in primary school to traffic-related air pollutants is associated with impaired cognitive development. METHODS AND FINDINGS: We conducted a prospective study of children (n = 2,715, aged 7 to 10 y) from 39 schools in Barcelona (Catalonia, Spain) exposed to high and low traffic-related air pollution, paired by school socioeconomic index; children were tested four times (i.e., to assess the 12-mo developmental trajectories) via computerized tests (n = 10,112). Chronic traffic air pollution (elemental carbon [EC], nitrogen dioxide [NO2], and ultrafine particle number [UFP; 10-700 nm]) was measured twice during 1-wk campaigns both in the courtyard (outdoor) and inside the classroom (indoor) simultaneously in each school pair. Cognitive development was assessed with the n-back and the attentional network tests, in particular, working memory (two-back detectability), superior working memory (three-back detectability), and inattentiveness (hit reaction time standard error). Linear mixed effects models were adjusted for age, sex, maternal education, socioeconomic status, and air pollution exposure at home. Children from highly polluted schools had a smaller growth in cognitive development than children from the paired lowly polluted schools, both in crude and adjusted models (e.g., 7.4% [95% CI 5.6%-8.8%] versus 11.5% [95% CI 8.9%-12.5%] improvement in working memory, p = 0.0024). Cogently, children attending schools with higher levels of EC, NO2, and UFP both indoors and outdoors experienced substantially smaller growth in all the cognitive measurements; for example, a change from the first to the fourth quartile in indoor EC reduced the gain in working memory by 13.0% (95% CI 4.2%-23.1%). Residual confounding for social class could not be discarded completely; however, the associations remained in stratified analyses (e.g., for type of school or high-/low-polluted area) and after additional adjustments (e.g., for commuting, educational quality, or smoking at home), contradicting a potential residual confounding explanation. CONCLUSIONS: Children attending schools with higher traffic-related air pollution had a smaller improvement in cognitive development.

The n-back test and the attentional network task as measures of child neuropsychological development in epidemiological studies.

Computerized neuropsychological tests offered several advantages for large epidemiological studies to assess child neuropsychological development. We aimed to evaluate the psychometric properties and criterion validity of 2 computerized tests (n-back and attentional network task [ANT]) used to assess the working memory and attention function, respectively. As part of the BREATHE (BRain dEvelopment and Air polluTion ultrafine particles in scHool childrEn) project, we evaluated the neuropsychological development of 2,904 children between 7 to 9 years of age. The main outcomes of the n-back test were d' scores and hit reaction time (RT) (HRT). The outcomes measured for ANT were incorrect responses, omissions, alerting, orienting, and conflict. We also collected data of child's sex, age, school achievement, ADHD symptomatology, behavioral problems, and maternal education. We observed that the d' scores and HRT showed acceptable internal consistency, reasonable factorial structure, as well as good criterion validity and statistical dependencies. Regarding the ANT, incorrect responses, omissions, and conflict score had acceptable criterion validity although the internal consistency of the ANT was low. We strongly recommend the use of these tests in environmental epidemiological studies as valid, objective, and easy-to-apply measures of child neuropsychological development.