Postponing Bedtime By Just 34 Minutes Could Increase Your Risk of High Blood Pressure

Even slight fluctuations in bedtime—as little as 34 minutes—may increase a person's risk of high blood pressure, or hypertension, new research shows.

The news comes from a March study published in Hypertension, a journal from the American Heart Association. Researchers found that people with irregular sleep patterns—like those who slept in on weekends or varied their bedtime and waking times during the week—were substantially more likely to have hypertension, compared to people with more consistent sleep schedules.1

The increased risk of high blood pressure remained even when people got the recommended amount of sleep each night, aside from an irregular schedule.

"This indicates that people may need to consider not only how long they sleep, but also recognize the importance of keeping a regular sleep schedule for optimal cardiovascular health," senior study author Danny Eckert, PhD, director of the Adelaide Institute for Sleep Health and a professor in the College of Medicine and Public Health at Flinders University in Australia, said in a press release.2

Here’s what experts had to say about how irregular sleep and high blood pressure might be linked, which groups may be at a higher risk, and tips to help make your sleep schedule more regular. 

Good Sleep Is More Than Just Getting Enough Hours

Though the link between poor quality sleep and issues such as hypertension, type 2 diabetes, and obesity is well documented, researchers wanted to investigate how sleep irregularities played a role.3

The study followed 12,287 adult participants—the majority of whom were male, middle-aged, and overweight—and tracked their sleep duration and timing through a device under their mattresses.1 The participants came from 20 different countries; some had hypertension while others did not. On average, the researchers took data from 181 nights of sleep and 29 blood pressure readings for each person.2

Defining high blood pressure as 140 mmHg over 90 mmHg or higher, the researchers found that irregular sleep can be considered “a risk marker for poor cardiovascular health.”1

As variations in bedtime increased, so did a person’s risk of hypertension. Slight changes in bedtime—about 30 minutes—increased someone’s risk by about a third, while larger variations such as 90 minutes saw a 92% increased risk of hypertension.2

Taking a more specific look, researchers found that an approximate 34-minute increase in sleep onset time irregularly—essentially sometimes going to bed about 34 minutes later than usual—was associated with a 32% increase in hypertension. Meanwhile, a 43-minute increase in sleep offset time—or sometimes waking up about 43 minutes later than normal—was associated with an 8.9% increase in hypertension.

How long people slept for was also significant. Those who slept too much or too little—defined as getting less than seven or more than nine hours of sleep consistently—were between 20% and 30% more likely to have hypertension. And sleeping for a different number of hours each night also seemed to cause an issue—those who varied their sleep duration by two hours or more had an 85% increased chance of having hypertension.2

Because the study participants were primarily male, middle-aged, and overweight, it’s possible that there are limitations on how applicable it is to the broader global population, explained Sadeer Al-Kindi, MD, cardiologist at University Hospitals Harrington Heart and Vascular Institute and associate professor at the Case Western Reserve University School of Medicine. People who are younger, women, or people who are not overweight may not see the same types of hypertension risks from irregular sleep habits.

But considering how common it is for people to change their bedtimes and sleep durations—whether for work, to get “caught up” on sleep on weekends, or for other reasons—the study could have large implications.

For now though, it may be too early to tell if any specific groups of people—whether that be night owls, those who work nights, or other people with more irregular sleep schedules—are more likely to experience hypertension risks.

“This study doesn't tell us a whole lot about which group we have to focus on,” Dr. Al-Kindi told Health. “There needs to be more research.”The other “caveat” to these findings, he added, is that the research only claims to have found a link between sleep irregularities and hypertension risk. That means it’s too early to say if fluctuating bedtimes or sleep duration is really causing the increased blood pressure risk, he said.

Why Does Sleep Have Such a Significant Impact on the Heart?

Researchers still don’t fully understand what mechanisms in the body link poor sleep to cardiovascular issues, Dr. Al-Kindi explained.

“The diseases of sleep are strongly linked with poor health outcomes,” Dr. Al-Kindi said. “Why [sleep irregularity] causes heart issues or high blood pressure in this case, is not fully understood."

During sleep, a person’s blood pressure usually goes down, which could explain why not sleeping enough or getting poor quality sleep could lead to hypertension.3 But it’s still unclear as to why changing up your bedtime or sleep duration could produce a similar effect.

There are a few possible explanations for what could be going on. For one, sleep irregularities may actually be hard on the body. For example, sleep changes may cause an increase in nighttime stress or fight-or-flight response, Dr. Al-Kindi said, which could raise blood pressure.

Irregular sleep may also affect a person’s circadian rhythm, said Clete Kushida, MD, PhD, chief and medical director at Stanford Division of Sleep Medicine. That circadian rhythm interruption could affect the body's ability to regulate blood pressure or other bodily processes.

But again, the cause and effect may also be flipped—it’s possible that hypertension is the real culprit manifesting in sleep irregularities or difficulties, Dr. Al-Kindi added.

The relationship between sleep and cardiovascular issues could also be explained by some other issue altogether, he said.

“There might be a common risk factor,” he said. “For example, air pollution or light pollution and other things have been linked with both cardiovascular disease and sleep disorders.”

But though the actual connection is still a bit fuzzy, the study makes it clear that the link is there.

“This study has highlighted that changing the timing of your sleep is important, since it can affect the normal physiological processes that are governed or associated with circadian and homeostatic processes,” Dr. Kushida told Health in a statement.

Regular and Routine Sleep Is Key

Though more research is needed to determine the relationship between sleep irregularities and hypertension for a wider range of people, the study’s findings are a good excuse for recommitting to a more consistent bedtime and sleeping schedule.

“Sleeping at the same time of the day, sleeping for the same period of time,” Dr. Al-Kindi said. “Regular sleep can be helpful in improving overall health, but also improving sleep efficiency and other things.”

People should try their best to pick a set time to go to sleep at night and wake up each day, Dr. Kushida said. Light therapy may help make this a bit easier, he explained, especially for people who have circadian rhythm disorders or otherwise have “irregular sleep-wake hours.” The therapy can help make people feel sleepy at night and awake in the morning on a more consistent schedule.

“Light therapy would involve bright light for 30 minutes within 5 minutes upon arising, and avoiding any bright light a few hours before bedtime,” he explained

Besides keeping a consistent bedtime and sleep duration routine, it’s also important to remember that getting enough good quality sleep is also protective against a wide range of health issues, everything from stroke risk to mental health issues.45 Adults should be getting at least seven hours of sleep each night, but about a third don’t meet that metric.