Key Takeaways:
- Irregular sleep significantly increased the risk of major adverse cardiovascular events (MACE), such as stroke or myocardial infarction.
- Higher Sleep Regularity Index (SRI) scores were associated with a reduced risk of MACE.
- Irregular sleep patterns elevated cardiovascular risks even among individuals meeting recommended sleep durations.
Study Findings:
A population-based cohort study published in Journal of Epidemiology & Community Health analyzed the relationship between sleep irregularity and cardiovascular health. The study involved 72,269 participants aged 40 to 79 years from the UK Biobank, who wore activity trackers for several days to determine their SRI scores.
Researchers categorized participants’ sleep patterns based on SRI scores:
- Regular sleep (SRI > 87)
- Irregular sleep (SRI < 72)
- Moderately irregular sleep (SRI 72–87)
Over an 8-year follow-up, the study revealed:
- Irregular sleepers had a 26% higher risk for MACE (HR = 1.26; 95% CI, 1.16–1.37) compared to regular sleepers.
- Moderately irregular sleepers had an 8% increased risk (HR = 1.08; 95% CI, 1.01–1.17).
- A near-linear relationship was observed between SRI and MACE risk reduction, with a median SRI score of 80.8 associated with an 18% lower risk for MACE (HR = 0.82; 95% CI, 0.71–0.94).
Sleep Duration and Cardiovascular Risk:
While meeting recommended sleep durations (7–9 hours for ages 18–64, and 7–8 hours for ages 65 and older) offset MACE risk for moderately irregular sleepers (HR = 1.07; 95% CI, 0.96–1.18), it did not fully mitigate risk for irregular sleepers (HR = 1.19; 95% CI, 1.06–1.35).
Potential Mechanisms:
The study proposed several mechanisms linking irregular sleep to adverse cardiovascular outcomes, including disruptions in circadian rhythms, hormonal imbalances, meal timing inconsistencies, inflammation, and immune system dysregulation.
Limitations and Implications:
Researchers noted limitations, including a low participant response rate and the observational nature of the study, which prevents establishing causation. Despite these limitations, the findings highlight the need for public health guidelines and clinical recommendations to prioritize sleep regularity for cardiovascular health.
“The interplay of mechanisms underscores the critical role of consistent sleep-wake patterns in maintaining cardiometabolic health,” said lead researcher Jean-Philippe Chaput, PhD, MSc, of the CHEO Research Institute.
