BACKGROUND:The objectives of this community-based study were to examine the overall and changing (1990-2007) frequency and impact on 30-day and 1-year death rates from multiple cardiovascular comorbidities in adults from a large central New England metropolitan area hospitalized with acute myocardial infarction (AMI). METHODS:The study population consisted of 9581 patients hospitalized with AMI at all 11 medical centers in the metropolitan area of Worcester, MA, during 10 annual periods between 1990 and 2007. The comorbidities examined included atrial fibrillation, diabetes, heart failure, hypertension, and stroke. RESULTS:Thirty-five percent of participants had a single diagnosed cardiovascular comorbidity, 25% had two, 12% had three, and 5% had four or more comorbidities. Between 1990 and 2007, the proportion of patients without any of these comorbidities decreased significantly, while the proportion of patients with multiple comorbidities increased significantly during the years under study. An increasing number of comorbidities was associated with higher 30-day and 1-year postadmission death rates in patients hospitalized with AMI. CONCLUSION:Patients hospitalized with AMI carry a significant burden of comorbid cardiovascular disease that adversely impacts their 30-day and longer-term survival. Increased attention to the management of AMI patients with multiple cardiovascular comorbidities is warranted.