The present study examined actigraphically evaluated sleep on the days surrounding the greatest earthquake in Japanese history. The Great East Japan Earthquake occurred unexpectedly on the third day of a 1-week actigraphy measurement. The subjects were eight elderly (73.1 ± 4.3 years, mean ± SD) individuals living in Sendai city, one of the largest cities damaged by the earthquake. All of the subjects wore their actigraph devices until 2 days after the earthquake. The results showed that wake after sleep onset (WASO) was significantly increased (118 ± 29 min, mean ± SE) the first night after the earthquake compared with pre-earthquake values (35 ± 12 min). The subjects described being awoken by frequent aftershocks the first night. This sleep debt was recovered the next day through significant increases in daytime napping and the length of nocturnal sleep periods resulting from earlier bedtimes. An electrical blackout that lasted 2–3 days seemed to be associated with earlier bedtimes by inducing a dark and cold environment. One subject who evacuated to a school gymnasium after the earthquake suffered severely disturbed sleep due to cold temperatures (nocturnal WASO over 180 min). These findings suggest that the environmental factors related to disrupted infrastructure might have considerable impacts on sleep in the first several days after the catastrophic disaster. The findings should be considered for future disaster preparedness initiatives.（8人の高齢者について、1週間のアクチグラフィ（手首の活動量から睡眠を評価する手法）測定中、その4日目に東日本大震災が発災した。発災当日は、余震の影響から睡眠中の中途覚醒が平均118 ± 29分に有意に増加した（発災前は平均35 ± 12分）。発災後に2-3日続いた停電期間中は就寝が早期化していた。8人中1人のみ小学校の体育館に避難したが、夜間中途覚醒時間が3時間を超す極度の不眠が認められた。これらの結果は、災害時における睡眠環境の変化が睡眠に大きく影響することを示唆しており、今後の備えを考える上で重要である。）
June 2014, Volume 72, Issue 2, pp 969-981
Kazue Okamoto-Mizuno
