An Irregular Sleep Schedule Can Raise the Risk of Heart Attack and Stroke, Study Finds

The researchers calculated the sleep regularity index (SRI) score of 72,269 participants between ages 40 and 79 from the UK Biobank (a database of UK-based research participants). Those with higher SRI scores had more consistent sleep-wake times (i.e., when they went to bed and woke up) and those with lower scores had inconsistent sleep-wake times.

So what does this mean for your sleep routine? And what happens if you stay up later tonight than you did last night? We talked to Raj Dasgupta, MD, a pulmonary, critical care, and sleep medicine doctor at the Keck School of Medicine at the University of Southern California, to learn more about how your sleep schedule can affect your risk of cardiovascular conditions like heart disease and stroke.

What did the study find?

The researchers found that irregular sleepers (people who went to bed and woke up at different times over the course of seven days) were 26 percent more likely to have a major cardiovascular event than regular sleepers (people who stuck closely to the same sleep and wake times over seven days). A cardiovascular event occurs any time there is damage to the heart muscle, which may include heart attack, heart failure, and stroke, among other cardiovascular conditions.

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But how exactly does your sleep schedule impact your heart in the first place? Researchers from the study explain that irregular sleep can disrupt your circadian rhythm (the body’s internal clock), hormone regulation (think: higher cortisol aka your stress hormone), immunity (your body’s ability to protect you from illnesses), and nervous system operations (which regulates your mood, thinking, and more). These natural processes are all in place to keep you functioning—and sleep is necessary for your body to get the rest it needs to function properly.

Well, what if you still get plenty of sleep? The study found that even when irregular sleepers got the recommended number of hours of sleep (more on that below), it didn’t offset the effect of an inconsistent schedule. Meaning: Keeping a consistent sleep-wake schedule might be better for your heart than getting a longer snooze.

Keep in mind that this is an observational study—so the researchers didn’t conclude that irregular sleep causes major cardiovascular events. It just means that there’s a strong link between your sleep schedule and overall heart health. The researchers also want us to know that while sleep is essential for our well-being, it’s not the only factor that affects our hearts. Your genetics, eating plan, exercise regimen, and potential underlying health conditions can also raise (or lower) your risk of heart disease.

A bit more on the connection between sleep and heart health

Sleep gives your heart a chance to kick its feet up and relax, says Dr. Dasgupta. “When you go to bed, [your] heart rate and blood pressure tend to go down,” he says. Without enough sleep, your heart doesn’t get that break, and the strain can increase your risk of high blood pressure, heart disease, heart attack, and stroke—all of which are common risk factors for heart disease.

Impact on stress

Stress hormones like cortisol, a hormone that rises when you wake up and decreases throughout the day, can stay elevated when you don’t get enough sleep. This hormonal spike can increase your blood pressure, cholesterol, blood sugar, and triglycerides (a type of fat in the blood), which can take a toll on your heart over time.

Impact on diet and exercise

Lack of sleep can even affect your lifestyle habits, too. Foods high in saturated fat, sugar, and sodium often pack more of an energy punch than heart-healthy foods, so they’re more appealing when you’re tired. That might get you through the day, but over time, these foods can raise your risk of developing cholesterol buildup in your arteries (your heart’s blood vessels), a common precursor to cardiovascular events. Let’s not forget that when you’re tired, you likely don’t have the time (or energy) to exercise, which is an important lifestyle habit for your overall well-being.

Impact on emotional well-being

Poor sleep not only makes emotional regulation more difficult, but it can disrupt important chemical messengers in your brain like serotonin—the “feel-good hormone” that is responsible for regulating your mood and other functions (like memory, digestion, and sexual desire). Therefore, sleep deprivation can lower your serotonin levels, making you vulnerable to mental health conditions like depression, which is another risk factor for heart disease.

So, how much sleep do you really need?

Okay, now that we know your sleep-wake consistency matters, let’s talk about how much sleep you should try to aim for as you’re building (or improving) your sleep schedule. In short: the answer is a little different for everyone. Your lifestyle habits, genetics, overall health status, and sleep debt can influence how much sleep is right for you. For example, you might feel refreshed with six hours of sleep, but your partner could use some shut-eye for a few more hours, even though you went to bed at the same time.

But, one of the most important factors that can help you figure out your baseline is your age. Experts recommend the following amount of sleep based on how old you are:

• Newborns (zero to three months): 14 to 17 hours of sleep
• Babies (four to 12 months old): 12 to 16 hours per day
• Toddlers (one to two years old): 11 to 14 hours per day
• Children (three to 12 years old): 10 to 12 hours per day
• Teenagers (13 to 18 years old): eight to 10 hours per day
• Adults (18 to 64 years older): seven to nine hours per day
• Older adults (65 and older): seven to eight hours per day

However, if you’re getting the recommended amount of sleep for your age and you still feel groggy when the alarm goes off, talking to your doctor is a good idea. They can help determine if you have an underlying sleep condition that is affecting your sleep quality and offer treatments to reduce the symptoms.

8 effective ways to get better sleep

Even if you’ve been a notorious irregular sleeper—you know who you are—it’s not too late to change your sleep habits, says Dr. Dasgupta. He suggests to:

• Stick to a (mostly) consistent bedtime and wake time—even on weekends, vacations, and holidays, if possible
• Keep a sleep journal to track your sleep and wake times so you know when it’s time for bed
• Put your alarm clock out of reach so you can’t hit the snooze button in the morning
• Go outside to get some sunlight as soon as possible after waking up (and if you don’t have access to direct sunlight, a light therapy lamp is a good alternative)
• Limit caffeine and alcohol consumption, especially before bed
• Exercise regularly, but not too close to bedtime
• Make your bed a screen-free, sleep-only zone, as blue light from your devices can keep you awake longer
• Get out of bed and do something relaxing for a few minutes (like reading or listening to calming music) if you’ve been under the covers for hours and are having difficulty falling asleep

Keep in mind: developing a consistent sleep schedule is going to happen overnight (no pun intended). Start slow—implement these strategies one step at a time to get your body used to a new and improved sleep routine.