Older individuals with a weekday bedtime later than midnight were associated with a greater risk of myocardial infarction. No elevated risks were observed according to weekend bedtimes.
A bedtime later than midnight on weekdays may significantly increase the risk of myocardial infarction (MI), according to study findings published in Frontiers in Cardiovascular Medicine.
As the most serious manifestation of coronary artery disease, MI impacts more than 7 million people worldwide each year, with several mediating factors indicated to increase risk, particularly sleep.
“Insufficient sleep can lead to reduced carbohydrate tolerance and increased sympathetic tone, which increase the risk of insulin resistance, obesity, hypertension, and may further contribute to MI,” explained researchers.
The link between sleeping habits and risk of adverse cardiovascular outcomes has been demonstrated in prior research, with sleep timing indices of bedtime and wake-up time found in a recent study to be associated with greater risk of MI.
Despite these findings, the study authors noted that the association between sleep timing (bedtime, wake-up time, and sleep midpoint) on incidence of MI, especially the impact of late bedtime, remains unknown.
In their analysis, they derived data from the Sleep Heart Health Study, a community-based, multicenter, prospective cohort study of individuals aged 40 years or older who filled out sleep habit questionnaires at baseline, underwent polysomnography monitoring between 1995 and 1998, and were followed up to 2011 for incidence of cardiovascular diseases (N = 4576; mean [SD] age, 63.4 [11.0] years; 87% White).
Participants’ sleep timings on weekdays and weekends were recorded or calculated via the sleep habits questionnaire, with bedtime divided into 4 categories:
Across the study cohort, 294 (6.4%) individuals with MI were reported during the 10.6 years of follow up, in which these patients were older, more likely to be men, and had a higher prevalence of smoking, diabetes, and hypertension than the non-MI group.
In assessing incidence of MI according to weekday bedtime, higher incidence of MI was observed most notably in those who slept later than 12:00 AM (9.2%), followed by those who went to sleep between 11:01 PM − 12:00 AM (7.0%), and 10:00 PM or earlier (6.9%), compared with those of the reference bedtime between 10:01 PM and 11:00 PM (5.1%; P = .008).
After adjusting for potential confounding factors, such as apnea–hypopnea index, body mass index, and sleep duration, findings of the multivariable Cox regression analysis indicated that sleeping on weekdays later than 12:00 AM was associated with a significantly greater risk of incident MI compared with the reference bedtime (HR, 1.628; 95% CI, 1.092-2.427; P = .017).
No significant association between late bedtime on weekends and MI was found–nor were any significant associations uncovered between late wake-up time and delayed sleep midpoint on both weekdays and weekends with the incidence of MI.
Following the study findings, authors concluded that sleep-targeted interventions addressing suitable bedtime on weekdays may be warranted to reduce the risk of MI.
Fan Y, Wu Y, Peng Y, et al. Sleeping late increases the risk of myocardial infarction in the middle-aged and older populations. Front Cardiovasc Med. Published online September 24, 2021. doi:10.3389/fcvm.2021.709468