Full moon and traffic accident-related emergency ambulance transport: A nationwide case-crossover study

Background: Several studies have examined the association between environmental factors and traffic accidents. However, the role of a full moon in triggering emergency ambulance transport due to road traffic casualties is unclear. Thus, we aimed to examine whether a full moon contributes to the incidence of emergency transport due to road traffic crashes. Methods: We acquired nationwide data on daily emergency transport due to road traffic crashes from all 47 prefectures of Japan from 2010 to 2014. We conducted a time-stratified case-crossover study using conditional Poisson regression to examine the relationship between the occurrence of a full moon and emergency transport due to road traffic crashes for each prefecture. Prefecture-level results were combined using a random-effects meta-analysis to evaluate nation-level estimates. Results: There were 842,554 cases of emergency transport due to road traffic crashes across 1826 nights (62 full moon nights: n=29,584; 1764 control nights: n=812,970). On days with a full moon, the pooled adjusted relative risk (RR) of emergency transport due to traffic accidents was 1.042 (95% confidence interval [CI], 1.021-1.063). Overall, 4.03% (95% CI: 2.06-5.93) of the cases (1192 cases) were attributable to full moon nights. Stratified analyses revealed a significant increase in emergency transport due to traffic accidents on full moon nights for males, people aged >= 40 years, and before midnight. Conclusions: Full moon nights are associated with an increase in the incidence of emergency transport due to road traffic crashes. These results indicate that public health strategies should account for full moon nights to decrease emergency transport due to traffic accidents. (C) 2018 Elsevier B.V. All rights reserved.