Objectives Earthquakes are a distressing natural phenomenon that can disrupt normal health-related behaviours. The aim of this study was to investigate changes in alcohol consumption behaviours in the immediate aftermath of mild to moderate earthquakes. Setting This retrospective cohort study was conducted at a large academic hospital in Tokyo, Japan from April 2004 to March 2017. Participants We included all adult patients presenting with acute alcohol intoxication in the emergency room. Primary and secondary outcome measures Our outcome was the number of such patients per 24 hours period comparing days with and without earthquake activity. We mainly focused on mild to moderate earthquakes (Shindo scale of less than 3). We conducted a simple generalised autoregressive conditional heteroscedasticity (GARCH) analysis, followed by a multivariate GARCH, including year-fixed effects and secular changes in alcohol taxation. Subanalyses were conducted by gender and age group. Results During the study period, 706 earthquakes were observed with a median Shindo scale of 2 (IQR: 1). During this period, 6395 patients were admitted with acute ethanol intoxication; the mean age was 42.6 (SD: 16.9) years and 4592 (71.8%) patients were male. In univariate analyses, the occurrence of daytime earthquakes was marginally inversely related to the number of acutely intoxicated patients (β coefficient: a '0.19, 95% CI a '0.40 to 0.01). This finding remained similar in multivariate analyses after adjustment for covariates. In analyses stratified by gender, the inverse association between daytime earthquakes and alcohol intoxication was only observed among men (p<0.03 for males and p=0.99 for females). In subanalyses by age, older people were less likely to be admitted to the hospital due to acute alcohol intoxication on days with daytime earthquakes (p=0.11), but this was not the case for younger people (p=0.36). Conclusion On days when a mild to moderate daytime earthquake occurred, the number of patients with acute alcohol intoxication was lower compared with days without earthquakes. Even milder forms of potentially catastrophic events appear to influence social behaviour; mild to moderate earthquake activity is associated with the avoidance of excessive alcohol consumption.
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