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Reduction in Acute MI After the Implementation of a Comprehensive Smokefree Ordinance - Reduction in Acute MI After the Implementation of a Comprehensive Smokefree Ordinance
Description:
The goal of the study was to determine the association between a Clean Indoor Air ordinance that prohibited indoor tobacco smoking on the incidence of myocardial infarction (MI) in a geographically isolated community setting.
Hypothesis:
Implementation of a Clean Indoor Air ordinance prohibiting smoking in public places will reduce the incidence of acute MI.
Study Design
Study Design:
Mean Follow Up: Six months
Patient Populations:
Resident of the specific geographic area, spent at least one night in the area prior to hospital admission or ate at least one meal at a restaurant in the area prior to symptom onset; and symptom onset prior to hospitalization
Exclusions:
Diagnosis of MI related to surgery or other in-hospital complications
Primary Endpoints:
Reduction in the incidence of acute MI
Drug/Procedures Used:
A Clean Indoor Air ordinance that prohibited indoor tobacco smoking in public places including bars, restaurants, casinos, and workplaces was passed in the geographically isolated community of Helena, Montana, and took effect June 2002. Charts for patients with a primary or secondary diagnosis of acute MI were reviewed for the period of December 1997 through November 2002 at the only hospital that serves the community.
Using zip codes, the incidence of MI was compared between residents of Helena and the surrounding communities, taking into account the time of month of the event to allow for seasonal effects in MI. Enforcement of the ordinance was discontinued in December 2002 by a court order.
Principal Findings:
The ordinance was associated with a reduction of -4.0 acute MI admissions per month for residents of Helena (p=0.002; 60% relative reduction) after adjustment for seasonal variability (month of MI). No significant reduction was observed in acute MI events for residents of the surrounding communities (+0.9 increase, p=0.22). Compliance with the ordinance was widespread, with only four violations reported among 118 businesses during the time the ordinance was in effect.
Interpretation:
Implementation of a Clean Indoor Air ordinance that prohibited indoor tobacco smoking was associated with an immediate reduction in the incidence of acute MI among residents in the community with the ordinance. Prior studies have shown that secondhand smoke increases the risk of cardiovascular events by up to 30% in family members of smokers.
Secondhand smoke has been shown to activate platelets and increase platelet aggregation, resulting in thrombus formation. It has also been shown to modify the endothelium leading to vasoconstriction. These effects occur within a relatively short exposure time to secondhand smoke in a matter of hours. Both of these factors increase the likelihood of cardiovascular events and reduce the ability to effectively respond to such events.
Given the effect of secondhand smoke on platelet aggregation and vasospasm, the reduction in acute MI observed in the present study is biologically plausible. Additional studies are warranted to determine if these results are replicable in other areas that have implemented smoke-free ordinances.
References:
Presented at Late-Breaking Clinical Trials, ACC 2003.
Keywords: Myocardial Infarction, Endothelium, Tobacco Smoke Pollution, Thrombosis, Platelet Aggregation, Blood Platelets, Vasoconstriction, Smoking
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