Sleep is commonly considered a nightly reset, but new research suggests that sleep timing may be just as important as duration.
Our sleep patterns mirror our daily rhythms and, by extension, these become indispensable for cardiovascular health. The body’s natural internal clock is beneficial for cardiovascular function when bedtimes and wake-up times remain at their usual schedule. With advances in wearable technology, these rhythms can be monitored in real time, helping us understand the impact of daily lifestyle patterns on heart health.
In a new study, researchers from the University of Oulu examined whether maintaining regular sleep schedules could predict the risk of major heart problems and cardiovascular death over 10 years in midlife adults.
Postdoctoral researcher Laura Nauha from the University of Oulu said, “Previous research has linked irregular sleep patterns to heart health risks, but this is the first time we’ve looked separately at variability in bedtime, wake-up time, and the midpoint of the sleep period, and their independent associations with major cardiac events.”
The study followed more than 3,200 Finnish adults over ten years, tracking their sleep patterns with wearable devices. Researchers examined whether participants had regular bedtimes, wake-up times, and sleep midpoints before categorizing sleep timing into three groups: regular, fairly regular, and irregular.
The researchers then looked at these patterns and their association with the occurrence of major cardiovascular events, including heart attacks, strokes, and cardiovascular death, taking into account age, sex, blood pressure, cholesterol levels, weight, and physical activity. It also studied people who slept little and those who slept more than eight hours to assess the impact of the amount of sleep.
During follow-up, 128 cases of a major heart problem were identified in the cohort. The highest risk was among those sleeping less than eight hours and those with irregular sleep schedules. Compared to those with stable routines, study participants with irregular bedtimes were twice as likely to experience heart attacks, strokes, or other deadly events. The study revealed that variability in sleep midpoints was also associated, whereas wake-up times showed no association pattern.
In summary, high variability in bedtimes or sleep midpoints was significantly associated with a greater risk of major cardiovascular events. In contrast, changes in wake-up times seemed to have little significance. For example, the bottom-line message is that regular bedtime could be as important for heart health as diet and exercise, emphasizing regular sleep behavior as a relevant target for prevention.
Nauha stated, “Our findings suggest that the regularity of bedtime, in particular, may be important for heart health. It reflects the rhythms of everyday life, and how much they fluctuate.”
