Public smoke-free legislation has been in place since July 2016 in a small city (Bibai) in Hokkaido (Japan); the effects of public smoke-free legislation in small cities in Japan on cardiovascular and cerebrovascular events have not been fully investigated. Monthly numbers of acute myocardial infarctions (AMIs) and stroke admissions were obtained from medical records, and the adjacent area, Naka-Sorachi, was used as a control region. According to the results of the Poisson regression, significant direct outcomes after the enactment of smoke-free legislation in Bibai city were not observed. After the implementation of the smoke-free legislation, the average monthly admission rates per population and risk ratios for AMI, stroke, and the combined outcome (AMI plus stroke) decreased in the Bibai region but increased in the control region (Naka-Sorachi), although there was no statistically significant difference between the two regions. However, significant interactions between the region (Bibai or Naka-Sorachi) and period (before or after the legislation) for stroke and the combined outcome were noted. Although a direct admission effect was not observed, the significant interaction indicated that Bibai had a decreasing trend in emergency admissions compared with the control region (Naka-Sorachi). Public smoke-free legislation in small cities may also decrease cardiovascular events.
Keywords: Acute myocardial infarction; Ecological study; Interaction; Smoking-free legislation; Stroke.