ISGlobal, Barcelona, Spain.
Universitat Pompeu Fabra (UPF), Barcelona, Spain.
PLoS Med. 2022 Jun 2;19(6):e1004001. doi: 10.1371/journal.pmed.1004001. eCollection 2022 Jun.
Road traffic noise is a prevalent and known health hazard. However, little is known yet about its effect on children's cognition. We aimed to study the association between exposure to road traffic noise and the development of working memory and attention in primary school children, considering school-outdoor and school-indoor annual average noise levels and noise fluctuation characteristics, as well as home-outdoor noise exposure.
We followed up a population-based sample of 2,680 children aged 7 to 10 years from 38 schools in Barcelona (Catalonia, Spain) between January 2012 to March 2013. Children underwent computerised cognitive tests 4 times (n = 10,112), for working memory (2-back task, detectability), complex working memory (3-back task, detectability), and inattentiveness (Attention Network Task, hit reaction time standard error, in milliseconds). Road traffic noise was measured indoors and outdoors at schools, at the start of the school year, using standard protocols to obtain A-weighted equivalent sound pressure levels, i.e., annual average levels scaled to human hearing, for the daytime (daytime LAeq, in dB). We also derived fluctuation indicators out of the measurements (noise intermittency ratio, %; and number of noise events) and obtained individual estimated indoor noise levels (LAeq) correcting for classroom orientation and classroom change between years. Home-outdoor noise exposure at home (Lden, i.e., EU indicator for the 24-hour annual average levels) was estimated using Barcelona's noise map for year 2012, according to the European Noise Directive (2002). We used linear mixed models to evaluate the association between exposure to noise and cognitive development adjusting for age, sex, maternal education, socioeconomical vulnerability index at home, indoor or outdoor traffic-related air pollution (TRAP) for corresponding school models or outdoor nitrogen dioxide (NO2) for home models. Child and school were included as nested random effects. The median age (percentile 25, percentile 75) of children in visit 1 was 8.5 (7.8; 9.3) years, 49.9% were girls, and 50% of the schools were public. School-outdoor exposure to road traffic noise was associated with a slower development in working memory (2-back and 3-back) and greater inattentiveness over 1 year in children, both for the average noise level (e.g., ‒4.83 points [95% CI: ‒7.21, ‒2.45], p-value < 0.001, in 2-back detectability per 5 dB in street levels) and noise fluctuation (e.g., ‒4.38 [‒7.08, ‒1.67], p-value = 0.002, per 50 noise events at street level). Individual exposure to the road traffic average noise level in classrooms was only associated with inattentiveness (2.49 ms [0, 4.81], p-value = 0.050, per 5 dB), whereas indoor noise fluctuation was consistently associated with all outcomes. Home-outdoor noise exposure was not associated with the outcomes. Study limitations include a potential lack of generalizability (58% of mothers with university degree in our study versus 50% in the region) and the lack of past noise exposure assessment.
We observed that exposure to road traffic noise at school, but not at home, was associated with slower development of working memory, complex working memory, and attention in schoolchildren over 1 year. Associations with noise fluctuation indicators were more evident than with average noise levels in classrooms.
道路交通噪声是一种普遍存在且已知的健康危害。然而，人们对其对儿童认知能力的影响知之甚少。我们旨在研究道路交通噪声暴露与小学生工作记忆和注意力发展之间的关系，同时考虑学校室外和室内的年平均噪声水平和噪声波动特征，以及家庭室外噪声暴露。
我们对巴塞罗那（西班牙加泰罗尼亚地区）38 所学校的 2680 名 7 至 10 岁的儿童进行了一项基于人群的随访。在 2012 年 1 月至 2013 年 3 月期间，儿童进行了 4 次计算机认知测试（n = 10112），用于测试工作记忆（2 回任务，可探测性）、复杂工作记忆（3 回任务，可探测性）和注意力不集中（注意网络任务，击中反应时间标准误差，毫秒）。在学年开始时，使用标准协议在学校室内和室外测量道路交通噪声，以获得加权等效声压级，即人类听力的日夜间平均水平（白天 LAeq，以分贝为单位）。我们还从测量结果中得出波动指标（噪声间歇性比，%；噪声事件数），并根据教室方向和教室在不同年份的变化对教室进行修正，获得个人估计的室内噪声水平（LAeq）。根据 2012 年巴塞罗那噪声图，使用欧盟噪声指令（2002 年）估计家庭室外噪声暴露（Lden，即 24 小时年平均水平的欧盟指标）。我们使用线性混合模型来评估噪声暴露与认知发展之间的关系，调整年龄、性别、母亲教育程度、家庭社会经济脆弱性指数、相应学校模型的交通相关空气污染物（TRAP）或家庭模型的室外二氧化氮（NO2）。儿童和学校被纳入嵌套随机效应。第一次访问时儿童的中位数年龄（25%分位数，75%分位数）为 8.5（7.8；9.3）岁，49.9%为女孩，50%的学校为公立学校。道路交通噪声的室外暴露与儿童在 1 年内工作记忆（2 回和 3 回）发展较慢以及注意力不集中有关，无论是平均噪声水平（例如，在街道水平每增加 5 分贝，2 回探测性降低 4.83 分[95%CI：-7.21，-2.45]，p 值<0.001）还是噪声波动（例如，在街道水平每增加 50 个噪声事件，降低 4.38 分[-7.08，-1.67]，p 值=0.002）。教室道路平均噪声水平的个体暴露仅与注意力不集中有关（2.49 毫秒[0，4.81]，p 值=0.050，每增加 5 分贝），而室内噪声波动与所有结果均有关。家庭室外噪声暴露与结果无关。研究局限性包括潜在的普遍性不足（我们的研究中有 58%的母亲拥有大学学位，而该地区为 50%）以及缺乏过去的噪声暴露评估。
我们观察到，与家庭室外噪声暴露相比，学校室外的道路交通噪声暴露与儿童在 1 年内工作记忆、复杂工作记忆和注意力发展较慢有关。与教室中的平均噪声水平相比，噪声波动指标与认知发展之间的关联更为明显。
