The Effect of Idaho's Clean Indoor Air Law on Myocardial Infarction Admission Rates in the City of Boise

Publication Date


Type of Culminating Activity


Degree Title

Master of Health Science, Health Services Leadership


Community and Environmental Health

Major Advisor

Sarah Toevs


Christopher Johnson


Conrad Colby


Secondhand smoke (SHS) has been shown to have adverse effects on the heart increasing the risk of an acute myocardial infarction (MI). SHS causes an estimated 53,000 deaths every year and there is evidence that nonsmokers are more susceptible to the deleterious effects of SHS than are current smokers. Although data supports the association between SHS and myocardial infarction rates, there is scant clinical evidence showing that smoking bans decrease myocardial infarction rates.

A ban on smoking in restaurants and other public buildings became effective in the State of Idaho on July 1, 2004. We used this opportunity to study the effect this smoking ban had on myocardial infarction rates in Boise City. Boise is a city of approximately 190,000 with two major hospitals serving the metropolitan area. Boise City residents admitted to either hospital with a primary diagnosis of myocardial infarction during the period of July 1, 2002 through June 30, 2005 were included in the study. Utilizing International Classification of Diseases, ninth revision (ICD-9) codes, we examined admission rates for myocardial infarction. Generalized additive models were run in SAS Proc GAM on daily MI counts using a Poisson distribution and a log link function, and controlled for weather, outdoor air quality, and time. Separate models were run for all patients and non-smokers.

There was a total of 808 Boiseans admitted with the diagnosis of MI during the 24 months prior to the smoking ban and a total of 389 admissions in the 12 months post ban for an overall crude rate reduction of 3.6% and a 9.4% crude rate reduction among nonsmokers. After controlling for weather, outdoor air quality and time the MI rate decreased 32% among nonsmokers (p=.002) and 18% among all patients (p=.068).

Idaho’s smoking ban may have decreased the number of MIs among nonsmokers in the City of Boise.

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