Impact of Qingdao's smoke‐free legislation on hospitalizations and mortality from acute myocardial infarction and stroke: An interrupted time series analysis

BACKGROUND AND AIMS: More than 20 cities in China have enacted local smoke-free laws that prohibit smoking in public places. Only two of these cities have examined the health impact of the law. Enacted in 2013, Qingdao's smoke free-law was stricter than most other municipal smoke-free laws because it did not allow designated smoking rooms. This study aimed to estimate the impact of Qingdao's smoke-free legislation on acute myocardial infarction (AMI) and stroke. DESIGN, SETTING AND PARTICIPANTS: We used an interrupted time-series design adjusting for underlying secular trends, seasonal patterns and meteorological factors to estimate the impact of the smoke-free law on AMI and stroke events among permanent residents aged 35 years or older in Qingdao, China. The study period was from 1 January 2010 to 31 December 2015, with a post-ban follow-up of approximately 2.5 years. MEASUREMENT: Outcome measures were weekly numbers of hospitalizations and deaths due to AMI/stroke. FINDINGS: A total of 10 371 and 56 101 patients were hospitalized, with a principal discharge diagnosis of AMI and stroke, respectively; 32 196 AMI and 49 711 stroke deaths occurred during the study period. Following the smoke-free legislation, an incremental 20% [95% confidence interval (CI) = 14-26%] and 8% (95% CI = 3-13%) decrease per year was observed in AMI and stroke hospitalization rates, respectively. Neither the immediate nor gradual change in AMI nor stroke mortality rates associated with the law was statistically significant (P > 0.05). Post-hoc subgroup analyses indicated that statistically significant reductions in AMI hospitalizations were evident among both the 35-64 (18% per year, 95% CI = 12-27%) and 65-84 (20% per year, 95% CI = 12-27%) age groups. Statistically significant reductions in stroke hospitalization were only in the older subgroup (13% per year, 95% CI = 8-18%). CONCLUSIONS: The 2013 smoke-free legislation in Qingdao, China was associated with reduction in hospitalization from acute myocardial infarction and stroke among permanent residents aged 35 years or older. There was no statistically significant reduction in mortality from acute myocardial infarctions or stroke.