Reduced Hospitalizations for Acute Myocardial Infarction After Implementation of a Smoke-Free Ordinance—City of Pueblo, Colorado, 2002–2006

January 2, 2009 / Vol. 57 / No. 51

MMWR Highlights

Smoking-Attributable Mortality

• Nine previous published studies have reported that laws making indoor workplaces and public places smoke-free were associated with rapid, sizeable reductions in hospital admissions for acute myocardial infarction (AMI), or heart attacks. However, most studies examined admissions for 1 year or less after the laws were implemented; thus, it was unknown whether the observed effect was sustained over time.
• The previously published Pueblo Heart Study Phase I (PHS Phase I) examined the impact of a comprehensive municipal ordinance in the City of Pueblo, Colorado, that made all workplaces and public places smoke-free as of July 1, 2003. The rate of heart attack admissions for city residents decreased from 257 per 100,000 person-years during the 18 months before the ordinance's implementation to 187 per 100,000 person-years during the 18 months after it, a decline of 27%.
• This MMWR extends the analysis for an additional 18 months through June 30, 2006 (PHS Phase II) and shows that the rate of heart attack admissions among city residents continued to decrease to 152 per 100,000 person-years, a decline of 19% from the Phase I post-implementation period and a decline of 41% from the pre-implementation period.
• These findings provide the first evidence that reductions in heart attack admissions after a smoking ban can be sustained during a 3-year period and suggest that smoke-free policies should be considered an important component of interventions to prevent heart disease morbidity and mortality.
• Two control sites were selected for comparison to the City of Pueblo: (1) the area of Pueblo County outside the City of Pueblo limits, and (2) El Paso County, including Colorado Springs, the most populous city in this county. Neither of the control sites had smoke-free laws in place during the pre-implementation, Phase I, or Phase II study periods. No significant changes were observed in AMI hospitalization rates in either of the control sites during any of the study periods.
• Smoke-free laws likely reduce heart attack hospitalizations both by reducing secondhand smoke exposure among nonsmokers and by reducing smoking, with the first factor making the larger contribution.

Secondhand Smoke Background

• Exposure to secondhand smoke (SHS) has immediate adverse cardiovascular effects, and prolonged exposure can cause coronary heart disease.
• Long-term SHS exposure, such as that occurring in a home or workplace setting, is associated with a 25%–30% increased risk for coronary heart disease in adult nonsmokers.
• SHS exposure causes an estimated 46,000 ischemic heart disease deaths annually among U.S. nonsmokers.
• Evidence indicates that SHS exposure can produce rapid adverse effects on the functioning of the heart, blood, and vascular systems that increase the risk for a cardiac event. Relevant mechanisms include effects on platelet function, endothelial function, and inflammation.
• Epidemiologic and laboratory data indicate that the dose-response relationship between tobacco smoke exposure and the risk for heart disease and AMI is nonlinear. These risks increase rapidly with relatively small doses of tobacco smoke such as those received from SHS and then continue to increase more slowly with larger doses.
• The evidence suggests that the acute effects of SHS exposure might be rapidly reversible.
• Eliminating smoking in indoor spaces is the only way to fully protect nonsmokers from SHS exposure.
• Studies have found that SHS exposure decreases substantially among nonsmoking employees of restaurants and bars and among nonsmoking adults in the general public after implementing smoke-free laws.
• Studies also have found that laws making restaurants and bars smoke-free are associated with rapid improvements in health indicators for restaurant and bar workers, including reductions in self-reported respiratory and sensory symptoms and objectively measured improvements in lung function.
• Compliance with smoke-free laws typically reaches high levels rapidly and then increases further over time. In addition, smoke-free laws are associated with increased adoption of smoke-free home rules.
• Smoke-free policies have been found to prompt some smokers to quit smoking. Because active smoking is a major risk factor for heart disease and AMI, this effect also would be expected to reduce heart disease and AMI rates at a population level.
• Continued decrease in AMI hospital admissions observed in this study might be a result of a combination of—
  • The immediate reduction in nonsmokers' SHS exposure that occurred when the City of Pueblo smoke-free ordinance was implemented.
  • Further reductions in this exposure that occurred because of increased compliance with the ordinance and increased adoption of smokefree home rules over time.
  • Increased quitting among smokers as a result of the ordinance and associated changes in social norms.