The Prognostic Significance of Sleep and Circadian Rhythm for Myocardial Infarction Outcomes: Case-Control Study

Abstract

Background: Myocardial infarction (MI) is a medical emergency resulting from coronary artery occlusion. Patients with acute MI often experience disturbed sleep and circadian rhythm. Most previous studies assessed the premorbid sleep and circadian rhythm of patients with MI and their correlations with cardiovascular disease. However, little is known about post-MI sleep and circadian rhythm and their impacts on prognosis. The use of actigraphy with different algorithms to evaluate sleep and circadian rhythm after acute MI has the potential for predicting outcomes and preventing future disease progression.

Objective: We aimed to evaluate how sleep patterns and disrupted circadian rhythm affect the prognosis of MI, using actigraphy and heart rate variability (HRV). Nonparametric analysis of actigraphy data was performed to examine the circadian rhythm of patients.

Methods: Patients with MI in the intensive care unit (ICU) were enrolled alongside age- and gender-matched healthy controls. Actigraphy was used to evaluate sleep and circadian rhythm, while HRV was monitored for 24 hours to assess autonomic nerve function. Nonparametric indicators were calculated to quantify the active-rest patterns, including interdaily stability, intradaily variability, the most active 10 consecutive hours (M10), the least active 5 consecutive hours (L5), the relative amplitude, and the actigraphic dichotomy index. Follow-ups were conducted at 3 and 6 months after discharge to evaluate prognosis, including the duration of current admission, the number and duration of readmission and ICU admission, and catheterization. Independent sample t tests and analysis of covariance were used to compare group differences. Pearson correlation tests were used to explore the correlations of the parameters of actigraphy and HRV with prognosis.

Results: The study included 34 patients with MI (mean age 57.65, SD 9.03 years) and 17 age- and gender-matched controls. MI patients had significantly more wake after sleep onset, an increased number of awakenings, and a lower sleep efficiency than controls. Circadian rhythm analysis revealed significantly lower daytime activity in MI patients. Moreover, these patients had a lower relative amplitude and dichotomy index and a higher intradaily variability and midpoint of M10, suggesting less sleep and wake activity changes, more fragmentation of the rest-activity patterns, and a more delayed circadian rhythm. Furthermore, significant correlations were found between the parameters of circadian rhythm analysis, including nighttime activity, time of M10 and L5, and daytime and nighttime activity_SD, and patient prognosis.

Conclusions: Patients with acute MI experienced significantly worse sleep and disturbed circadian rhythm compared with healthy controls. Our actigraphy-based analysis revealed a disturbed circadian rhythm, including reduced daytime activities, greater fluctuation in hourly activities, and a weak rest-activity rhythm, which were correlated with prognosis. The evaluation of sleep and circadian rhythm in patients with acute MI can serve as a valuable indicator for prognosis and should be further studied.

Keywords: actigraphy; activity; circadian rhythm; heart rate variability; myocardial infarction; nonparametric analysis; prognosis; sleep.

Figure 1

Timeline of the study. Patients with myocardial infarction (MI) underwent actigraphy after admission to the intensive care unit (ICU) and kept wearing the device until discharge. They also underwent heart rate variability (HRV) evaluation for the initial 24 hours in the ICU. After discharge, they were followed for 6 months to evaluate the prognosis.

Figure 2

The flowchart outlines the methodological framework for circadian rhythm analysis in the study, from patient recruitment to the processing and analysis of actigraphic data. The chart includes the criteria for patient enrollment based on age and diagnosis, and patients with recording of less than 3 days were excluded from the circadian rhythm analysis. HRV: heart rate variability; ICU: intensive care unit; MI: myocardial infarction.

Figure 3

Representative actograms for the myocardial infarction (A) and healthy control (B) groups.

Figure 4

Protocol for heart rate variability (HRV) monitoring within the initial 24 hours of intensive care unit (ICU) admission for patients with acute myocardial infarction (MI). The chart delineates the steps from HRV recording to data analysis.

Figure 5

The average circadian activity template of the myocardial infarction (MI) patient cohort, synthesized from actigraphy data. It depicts the group’s collective rest-activity cycles over a standard 24-hour period, highlighting the marked decreased amplitude of daytime and nighttime activity changes observed after acute MI.

Figure 6

Acrophase map showing the timings of the midpoint of M10 of myocardial infarction (MI) patients and healthy controls. Patients with MI had higher individual variability in the timing of the midpoint of M10 compared to healthy controls. M10: most active 10 consecutive hours.