Association of wake time and the onset of myocardial infarction. Triggers and mechanisms of myocardial infarction (TRIMM) pilot study. TRIMM Study Group.

A morning increase in onset of acute myocardial infarction (MI) has been documented, but its association with wake time and possible triggering events is unclear. The community-based, ongoing Triggers and Mechanisms of Myocardial Infarction (TRIMM) study was designed to investigate the factors associated with the transition from chronic coronary artery disease to acute MI. During the pilot phase in 1989, 224 consecutive hospitalized MI patients (176 men and 48 women, aged 60.3 +/- 9.2 years) of the prospectively defined Monitoring of Trends and Determinates of Cardiovascular Disease (MONICA) Augsburg MI register were interviewed 16.8 +/- 6.5 days after the event. The frequency of onset of MI was significantly higher (p less than 0.01) during the morning from 6 to 9 AM compared with other times of day. After adjustment for individual wake times, the peak of onset of MI was markedly sharper; the relative risk of MI during the 3-hour peak interval (the 3 hours after awakening) compared with other times of day increased from 1.8 (95% confidence interval, 1.3-2.4) to 2.4 (95% confidence interval, 1.8-3.1). Sixty-seven percent of the patients reported possible acute triggers of MI and/or unusual life events; among those, 52% reported stress or emotional upset. The TRIMM pilot study demonstrated the feasibility of a community-based study of possible triggering events of MI. The circadian variation of MI appears to result primarily from increased onset after awakening. This narrowing of the time frame of increased risk of MI should facilitate study of pathogenic mechanisms and aid in the design of more effective preventive regimens.