The competition for our attention from a connected world makes it hard sometimes to turn off the distractions and go to sleep. But researchers have discovered by analyzing data from wearable technology that not having a consistent sleep time makes your heart beat faster.
Lack of sleep has been linked to an increased risk for numerous health conditions like diabetes, stroke and cardiovascular disease so an emphasis has been placed on encouraging people to get at least seven hours of sleep each night. But science is showing there is more to consider.
Researchers at the University of Notre Dame have discovered a correlation between someone’s bedtime and their resting heart rate. Study subjects who went to bed just 30 minutes later than normal had a significantly higher resting heart rate that lasted even into the next day.
"We already know an increase in resting heart rate means an increased risk to cardiovascular health," said Nitesh Chawla, director of the Center for Network and Data Science at Notre Dame and a lead author of the study. "Through our study, we found that even if you get seven hours of sleep a night, if you're not going to bed at the same time each night, not only does your resting heart rate increase while you sleep, it carries over into the next day."
Chawla and his team had access to data from 255,736 sleep sessions from 557 college students who wore Fitbit devices over a four-year period. These wrist-worn devices were used to track heartrate and sleep times.
Researchers used a one-hour window surrounding a student’s median bedtime to determine their normal bedtime. The data showed when a student went to bed between one and 30 minutes later than normal it resulted in a significant increase in resting heart rate that night which lasted into the next day.
Researchers also found going to bed earlier than normal had an effect, but the amount of impact depended on how early. There was virtually no difference if students went to be less than 30 minutes early. More than 30 minutes early meant the students would have an elevated resting heart rate but that rate leveled out while they slept.
Chawla said circadian rhythms, medications and lifestyle factors all impact healthy sleep habits but it’s also important to consider consistency.
"For some, it may be a matter of maintaining their regular 'work week' bedtime through the weekend," said Chawla. "For shift workers and those who travel frequently, getting to bed at the same time each night is a challenge. Establishing a healthy bedtime routine—as best you can—is obviously step number one. But sticking to it is just as important."