https://orcid.org/0000-0002-8384-8554
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Abstract
Purpose
Large-scale natural disasters have an enormous physical and mental impact, immediately after they occur, on people living near the central disaster areas. It is known that, in the early stages, a seismic disaster triggers high rates of symptoms for insomnia, depression, and anxiety. However, little information is available about their medium- to long-term clinical outcomes. In this study, we conducted a repeated cross-sectional nationwide questionnaire survey to clarify changes in the prevalence of insomnia and its background factors after the Great East Japan Earthquake, a huge earthquake with a moment magnitude of 9.0 that occurred on March 11, 2011.
Methods
We conducted a repeated cross-sectional survey in November 2009 (pre-earthquake, 1224 participants), July 2011 (4 months post-earthquake, 1259 participants), and August 2012 (18 months post-earthquake, 1289 participants) using stratified random sampling from 157 Japanese sites.
Results
Compared to 2009, the prevalence of insomnia statistically increased nationwide immediately post-disaster (11.7% vs 21.2%; p < 0.001) but significantly decreased in 2012 compared to immediately after the earthquake (10.6% vs 21.2%; p < 0.001). In 2011, insomnia was most frequent in the central disaster area. Multivariable logistic regression models demonstrated the association between the following factors and increased risk of insomnia: being a woman (odds ratio [OR] 1.48, 95% confidence interval [CI]: 1.00–2.19), being employed in 2009 (OR 1.74, 95% CI: 1.15–2.62), and being of younger age group (20–64 years) in 2011 (OR 1.64, 95% CI: 1.12–2.42) and 2012 (OR 2.50 95% CI: 1.47–4.23). Post-earthquake, the prevalence of insomnia symptoms in men increased, while the gender difference decreased and was no longer statistically significant. Additionally, insomnia was associated with psychological distress (scores ≥5 on the Kessler Psychological Distress Scale) in 2011 and 2012.
Conclusion
This study demonstrated that the prevalence of insomnia was significantly higher after the earthquake. Moreover, individuals with insomnia were more likely to experience psychological distress after the earthquake that continued until 2012.
Abbreviations
CI, confidence interval; DIS, difficulty initiating sleep; DMS, difficulty maintaining sleep; DSQ, deteriorated sleep quality; EMA, early morning awakening; K6, Kessler Psychological Distress Scale; OR, odds ratio.
Data Sharing Statement
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
Ethics Approval and Consent to Participate
The Akita University Graduate School of Medicine Ethics Committee approved this study (approval no. 2522).
Acknowledgments
We thank Dr Sawako Minamizono for her advice and assistance with the statistical analysis. Dr Norio Watanabe is now affiliated with the Department of Psychiatry, Soseikai General Hospital, Kyoto, Japan.
Author Contributions
All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.
Disclosure
Dr Makoto Honda reports personal fees from Takeda Pharmaceutical Co Ltd, Ono Pharmaceutical Co Ltd, and Alfresa Corporation, outside the submitted work. The authors report no other conflicts of interest in this work.