Objectives

To determine the impact of bushfires on children’s physical activity.

Design

Natural experiment comparing device-measured physical activity and air quality index data for schools exposed and not exposed to the Australian bushfires.

Methods

Participants were drawn from 22 schools participating in a cluster randomised controlled trial of a school-based physical activity intervention that coincided with the 2019 Australian bushfires. Students in Years 3 and 4 (8–10 years old) provided data. We used propensity score matching to match 245 exposed and 344 control participants.

Main outcome measures

Minutes of moderate and vigorous physical activity.

Results

The bushfires had minimal effect on children’s average weekly physical activity. Analysis of acute effects showed children maintained their levels of physical activity up to an estimated turning point of air quality index of 737.08 (95% CI = 638.63, 835.53), beyond which daily physical activity levels dropped sharply. Similar results were found for girls and boys and for children from low-to-average and higher socio-economic backgrounds.

Conclusions

Children’s physical activity was not strongly influenced by the presence of smoke and targeted public health advice during the bushfires might not have had the intended effect of reducing children’s outdoor physical activity. Only when air quality deteriorated to approximately 3.5 times the Air Quality index threshold (>200) deemed ‘hazardous’ by the Australian Department of Health did children’s physical activity decline. Public health agencies should re-evaluate the effectiveness of health messages during bushfires and develop strategies to mitigate risks to children’s health.

中文翻译：

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澳大利亚森林大火对儿童体育锻炼的影响

目标

确定丛林大火对儿童身体活动的影响。

设计

自然实验，比较暴露于和未暴露于澳大利亚丛林大火的学校用设备测量的身体活动和空气质量指数数据。

方法

参加者来自22所学校，他们参加了一项基于学校的体育活动干预的随机分组随机对照试验，该试验与2019年澳大利亚丛林大火相吻合。3年级和4年级（8-10岁）的学生提供了数据。我们使用倾向得分匹配来匹配245位暴露参与者和344位对照参与者。

主要观察指标

分钟的中等强度和剧烈运动。

结果

丛林大火对儿童每周的平均体力活动影响很小。急性影响分析表明，儿童的体育活动水平一直保持到空气质量指数的估计转折点737.08（95％CI = 638.63，835.53），超过该水平，每日的体育活动水平急剧下降。对于男孩和男孩以及低至中等和较高社会经济背景的儿童，也发现了类似的结果。

结论

儿童的体育活动不受烟雾的强烈影响，在森林大火期间有针对性的公共卫生建议可能未达到减少儿童户外体育活动的预期效果。只有当空气质量恶化到澳大利亚卫生部认为“危险”的空气质量指数阈值（> 200）的3.5倍时，儿童的体育活动才会下降。公共卫生机构应在森林大火期间重新评估健康信息的有效性，并制定减轻儿童健康风险的策略。