Background To examine changes in the incidence of out-of-hospital cardiac arrest (OHCA) with cardiac origin in the non-disaster areas of Japan before and after the Great East Japan Earthquake of 11 March 2011.

Methods The 35 prefectures in Japan with no dead or missing caused directly by the earthquake were defined as the non-disaster areas. Data of adult OHCA patients in the non-disaster areas from March 4 to 24 each year from 2005 to 2011 were obtained from the All-Japan Utstein Registry. Risk ratios (RRs) of OHCA incidence and 95% CIs were estimated for three specific weeks in 2011 (1 week before and 2 weeks after the earthquake) by applying multivariable Poisson regression model. Incidence in the corresponding periods of March 4–24 from 2005 to 2010 was set as the baseline risk.

Results In the analyses from a total of 17 353 OHCA patients, the incidence statistically significantly increased in the first week after the earthquake in all adults (adjusted-RR=1.13, 95% CI=1.05 to 1.22, p=0.001) and in elderly women (adjusted-RR=1.23, 95% CI=1.11 to 1.37, p<0.001).

Conclusions The Great East Japan Earthquake caused the increase of OHCA among elderly women even in the non-disaster areas.