An irregular sleep-wake cycle, even when fulfilling the recommended amount of sleep, is linked with an increased risk of major cardiovascular events, including heart attack and stroke. This association was revealed in a study published in the Journal of Epidemiology & Community Health, which delves deeper into the impact of sleep patterns on health, a relatively less explored area than sleep duration.
The research utilised data from 72,269 individuals aged between 40 and 79 who were participants in the UK Biobank study and had no prior history of significant cardiovascular events. These participants were monitored over a week with an activity tracker that recorded their sleep. This data helped calculate each individual’s Sleep Regularity Index (SRI) score. Based on the SRI scores, the participants were categorised into three groups: those with a score above 87 were deemed to have regular sleep patterns, scores below 72 indicated irregular sleepers and scores between these values were considered moderately irregular.
Over the following eight years, the study tracked incidents of cardiovascular mortality, heart attack, heart failure, and stroke using death registries and hospital records. This enabled researchers to correlate the risk of these cardiovascular events with the participants’ sleep patterns. After adjusting for several potential influencing factors such as age, lifestyle, diet, and mental health, the findings indicated that individuals with irregular sleeping patterns were 26% more likely to experience a major cardiovascular event compared to those with regular sleep patterns. Those with moderately irregular sleep patterns exhibited an 8% increased risk.
Further analysis highlighted a nearly linear relationship between lower SRI scores and higher risk of cardiovascular events, with a more significant decrease in risk noted at higher SRI scores. Interestingly, while 61% of regular sleepers met the recommended sleep duration of 7 to 9 hours for adults aged 18 to 64 and 7 to 8 hours for those over 65, only 48% of irregular sleepers achieved this. However, meeting the recommended sleep duration did not significantly mitigate the risk for irregular sleepers, though it did reduce the risk for moderately irregular sleepers.
It’s crucial to note that this observational study cannot definitively establish causality. The researchers acknowledged several limitations to their findings. For example, the sample size, although significant, may not perfectly reflect the broader UK population. Sleep patterns were assessed for one week, and the activity tracker could not differentiate between quiet wakefulness and actual sleep. Furthermore, considering only the most extended sleep period, the SRI algorithm did not account for napping.
Despite these limitations, the study’s results strongly suggest that irregular sleep significantly correlates with the risk of major adverse cardiovascular events in adults, regardless of meeting sleep duration recommendations. The findings underscore the importance of sleep regularity over mere duration in influencing cardiovascular health risks.
The researchers advocate for a greater focus on sleep regularity in public health guidelines and clinical practice, highlighting its potential role in cardiovascular health management. This shift in focus could lead to more effective strategies in preventing cardiovascular events, emphasising how long we sleep and how consistently we adhere to our sleep schedules.
More information: Jean-Philippe Chaput et al, Sleep regularity and major adverse cardiovascular events: a device-based prospective study in 72 269 UK adults, Journal of Epidemiology and Community Health. DOI: 10.1136/jech-2024-222795
Journal information: Journal of Epidemiology and Community Health Provided by BMJ Group
