To compare the cardiovascular risk of exercise in the morning and afternoon in patients with established heart disease.
Retrospective cohort study. Patients: Patients with established heart disease referred for participation in a comprehensive cardiac rehabilitation program.
Supervised, submaximal exercise (1 hour three times per week) performed either in the morning (7:30 AM) or the afternoon (3 PM).
Documented cardiac events that occurred while patients were exercising in the rehabilitation programs.
There were five cardiac events in 168 111 patient-hours of exercise in the morning, with an incidence of 3.0±1.3 events per 100 000 patient-hours. There were two events during the 84 491 patient-hours of exercise in the afternoon, for an incidence of 2.4±1.5 events per 100 000 patient-hours (not significant). The risk ratio of cardiac events during exercise in the morning compared with the afternoon was 1.27 (95% confidence interval, 0.25 to 6.55).
In patients with coronary artery disease, the incidence of cardiac events is low during regular, submaximal exercise whether performed in the morning or the afternoon.(Arch Intern Med. 1993;153:833-836)