Why Does My Heart Rate Spike When I'm Asleep?
Your body undergoes a number of important recuperative processes during sleep, from cell renewal to muscle repair to restorative brain activity. Changes in breathing, oxygen levels, and heart rate occur as well. These actions are essential to your long-term health. While having a slight fluctuation in heart rate during sleep is normal, it is important to understand the causes of more noticeable spikes in your heart’s number of beats per minute.
Sleep apnea and heart rate fluctuation
A common cause of a rising heart rate during sleep is a lack of oxygen, which is often brought on by obstructive sleep apnea. This is a condition where a person’s normal breathing frequency is reduced or sometimes flat-out stopped during sleep. The effort to breathe persists, but with the upper airway blocked, oxygen levels drop and carbon dioxide levels rise.
These blockages involve the softening of the muscles around the throat, soft palate, uvula, and tongue base. When the occurrence of these interruptions—referred to as apneas—are in excess (more than five times per hour of sleep), a formal diagnosis of obstructive sleep apnea (OSA) from a doctor may follow.
When breathing ceases during sleep, the brain recognizes that things aren’t right, and wakes the sleeping person up, kickstarting normal breathing functions once again. Not only is a person’s sleep quality compromised because of OSA, these apneas also cause the heart to beat faster than usual.
Heart rate and oxygen levels
Let’s walk through what happens when your breathing stops and your brain is cut off from a sufficient oxygen supply while you sleep.
When an apnea occurs, regular respiratory function ceases. As a result, the heart kicks into high gear, thinking that the reason your body isn’t getting its proper oxygen supply is because it simply isn’t pumping blood fast enough. This is actually similar to what happens during strenuous exercise, and why the heart beats faster to distribute oxygen throughout your body.
But this time, you’re not exercising—you’re asleep, and you’re not breathing. The heart wants to compensate for this deficit in oxygen and pumps faster and faster, but the blood moving through your circulation is de-oxygenated and isn’t helping you out very much. At around this time, your brain’s panic mode is triggered, and it rouses you out of your sleep. This is accompanied by a burst of cortisol (stress hormone). Your pulse is spiking, you wake up and gasp for breath, and in doing so, take a big gulp of air.
Finally, your body gets the oxygen it needs, and your pulse goes down again. But the damage from this disruptive episode has already been done. Namely, your sleep has been disrupted, even if you don’t remember waking up, and your pulse has been much higher than it needs to be.
Sleep apneas can happen dozens, sometimes hundreds, of times each night. A recent report found that incidents of OSA raises heart rates in patients. Spikes in your heart rate at that frequency isn’t healthy in the long term—these repeated episodes stress the health of your heart.
Another factor that contributes to increased heart rate is the instinctual “fight or flight” response. This surge of adrenaline happens when we’re faced with something our brain perceives as being a real danger, and we must make the split-second decision to either face the threat or run from it in order to stay safe. When our body is deprived of oxygen, this response also raises our heart’s beats per minute.
Methods for increasing oxygen intake
There are a number of ways for people to reduce the frequency of these apnea events and avoid unnecessary spikes in their heart rate. Finding out which method works the best depends on the individual, and sometimes requires a little trial and error, or a combination of treatments. Here are some more common strategies:
- Side sleeping - Many studies indicate that sleeping on your side allows for the best oxygen intake overall. Sleeping on one’s back should generally be avoided as it often worsens sleep-disordered breathing like snoring and sleep apnea.
- Special sleeping tools - A variety of consumer products are on the market to help you sleep in the position that will optimize your oxygen intake.
- Weight loss - Or, more specifically, decreasing the circumference of your neck through weight loss. While sleep apnea affects all body types, decreasing neck circumference is a better predictor of OSA than obesity alone. Men should target neck sizes less than 17 inches and women should aim for fewer than 16 inches.
- Oral appliances - Custom molded to fit over your teeth, this appliance gently slides the jaw forward to keep your airway open and your tongue out of the way while you sleep. Usually recommended for those with mild or moderate cases of sleep apnea.
- CPAP - A special breathing machine that delivers increased airflow through a fitted mask, it has proven highly effective in regulating respiratory function for those who use it consistently.
Despite some stereotypes, loud snoring and sleep apneas are not just relegated to those who are older and overweight. OSA can affect almost anyone, regardless of gender, age, weight, or fitness level.
Consistently healthy, restorative nights of sleep can have long-lasting benefits, and reducing the number of apneas each night is a step in the right direction. The fewer instances of apnea, the less your body will struggle to find air, and as a result, your heart rate will not spike as much.
Brandon R. Peters, M.D., is board-certified in both neurology and sleep medicine and currently practices at Virginia Mason Medical Center in Seattle. He is also a clinical faculty affiliate at Stanford University's School of Medicine in the Department of Psychiatry and Behavioral Sciences. His latest book, Insomnia Solved, is available on Amazon.