This study investigates the relationship between device-measured sleep regularity and the risk of major adverse cardiovascular events (MACE).
It also examines whether adequate sleep duration can mitigate or eliminate the impact of irregular sleep on MACE risk.
Methods
Using data from the UK Biobank, researchers included adults aged 40-79. Participants wore wrist accelerometers for seven days to record data. A validated algorithm calculated each participant’s Sleep Regularity Index (SRI), which categorized them into irregular (SRI <71.6), moderately irregular (SRI 71.6-87.3), and regular (SRI >87.3, reference group). MACE and its subtypes (myocardial infarction, heart failure) were assessed through hospital and death records.
Results
The study analyzed data from 72,269 participants without a prior history of MACE, with a follow-up period of 8 years. Compared to regular sleepers, those with irregular sleep patterns had a 26% higher MACE risk (hazard ratio 1.26, 95% CI 1.16-1.37), while moderately irregular sleepers had an 8% increased risk (hazard ratio 1.08, 95% CI 1.01-1.70). The continuous analysis of SRI revealed a near-linear relationship, where higher regularity correlated with a greater reduction in MACE risk. Joint analyses indicated that achieving the recommended sleep duration neutralized the MACE risk for moderately irregular sleepers (hazard ratio 1.07, 95% CI 0.96-1.18) but not for those with irregular sleep (hazard ratio 1.19, 95% CI 1.06-1.35).
Irregular sleep significantly increases the risk of MACE, even when sleep duration is sufficient. These findings support incorporating sleep regularity into public health guidelines and clinical practices as a critical cardiovascular risk factor.
Can Irregular Sleep Wake Cycle Increase Risk of Major Cardiovascular Events?
Video by Medical Dialogues
Study Highlights
Analyzing device-recorded SRI data, the study found a strong association between irregular sleep and elevated MACE risk among adults. Importantly, the results emphasized that sleep regularity might have a more significant impact on MACE risk than sleep duration. Joint analyses showed that irregular sleep increased MACE risk regardless of sleep duration adherence. This research underscores the need to prioritize sleep regularity in public health and cardiovascular disease prevention efforts.
Research Significance and Mechanisms
Although limited studies have explored the connection between sleep regularity and cardiovascular risk, existing evidence suggests that irregular sleep negatively affects health. For instance, prior research linked irregular sleep to subclinical atherosclerosis. Another study in a multi-ethnic cohort found that individuals with the most irregular sleep had over twice the cardiovascular risk compared to those with the highest regularity within less than five years of follow-up. This study addressed previous limitations, such as small sample sizes and inadequate methodologies, by utilizing SRI for more reliable risk assessment.
Irregular sleep disrupts circadian rhythms, hormone regulation, meal timing, inflammation, and immune functions. Possible mechanisms include glucose and lipid metabolism imbalances, insulin resistance, and heightened sympathetic nervous system activity, which collectively increase risks of hypertension, endothelial dysfunction, and cardiovascular or metabolic diseases.
Public Health and Policy Recommendations
The National Sleep Foundation emphasizes that sleep regularity is crucial for health and performance. While the American Heart Association includes sleep duration as part of its “Life’s Essential 8,” evidence suggests that sleep regularity may be a superior indicator of sleep health. Future research should focus on whether improving sleep regularity could enhance cardiovascular outcomes.
Limitations
Despite its large sample size, the study may not fully represent broader populations. Additionally, covariates were evaluated at a single time point, which might not capture long-term changes. Sleep data were based on a single week, potentially limiting the reflection of long-term patterns. However, prior studies confirm that one week of data is sufficient for reliable sleep regularity assessments.
This research is the first to examine long-term associations between sleep regularity and MACE risk. It highlights that even meeting recommended sleep durations does not offset the heightened risk posed by irregular sleep. Future studies should evaluate the potential cardiovascular benefits of interventions aimed at improving sleep regularity.
