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Your Heart, Your Sleep – Sleep And Cardiovascular Health

If you were to enumerate three things that are bad for your heart and are likely to cause a heart attack, what would they be? Do you feel that poor sleep is as big of a factor as a lack of physical exercise or smoking? 

As it turns out, sleep does play a big role. According to the National Sleep Foundation, poor sleepers run a higher risk of developing cardiovascular disease or coronary heart disease than those who sleep sufficiently. It doesn’t matter what your age or weight is or whether you smoke or exercise. In any of those groups short sleepers seem to suffer the most.

Those who sleep excessively should also be aware – it’s easy to find information on how short sleep affects the heart (perhaps because we are a sleep-deprived nation), but sleeping longer than recommended (9 hours or more) bears the exact same dangers as sleeping less than 6 hours.

How inadequate sleep affects the heart

Sleep brings balance to the body – it restores damaged cells and tissues, lowers blood pressure, and relieves stress that our overworked muscles and brain centers endure. Poor sleep does the opposite. 

The exact link between sleep and heart disease isn’t completely clear but what we know for sure is that insufficient sleep disrupts many processes in the body whose joint abnormal activity works against the heart. 

When we are sleep deprived our blood pressure and heart rate go up. Stress hormones also increase in the system and they tend to be high the next night which could keep you awake or simply cause poor quality sleep. Hypertension tends to develop as a consequence of long-term sleep deprivation.

A 2019 study showed that short sleep is associated with low-key atherosclerosis in various parts of the body. The same was found for fragmented sleep, which includes multiple awakenings during the night (also known as sleep-maintenance insomnia). Some sleep disorders could cause fragmented sleep, like obstructive sleep apnea (OSA) and restless leg syndrome.

Other problems include the increased inflammation and blood glucose metabolism. First, as the inflammation is more widely present in the body a protein called C-reactive protein (CRP) increases. CRP is an inflammation marker whose presence is strongly linked to the incidence of heart attacks.

Inadequate sleep disrupts the glucose metabolism and hormone balance. For this reason underslept people tend to reach for unhealthy choices and numerous snacks, even though their bodies can’t deal with it properly. Obese people are much more likely to be poor sleepers – obesity can cause poor sleep and poor sleep could eventually lead to obesity. Either way, being overweight is another problem that connects sleep and heart health.

Napping can help

According to a recent study we wrote about, napping can decrease the risk of heart attacks and heart disease. The benefit of taking naps lies in the fact that when we nap, we can reduce some of the stress that accumulated from insufficient sleep or to simply relax and get some rest after a stressful day. When we nap our blood pressure decreases and we become slightly more refreshed than before the nap.

Naps are good as long as they aren’t too frequent or too long  – once or twice a week for about 30 minutes is the most beneficial. 

Napping more than two or three times a week may indicate that you’re not getting enough sleep so if you are a frequent sleeper you should ask yourself what you can do to improve your nightly rest.

Naps longer than 30 minutes could reduce your need to sleep at night and postpone your bedtime.

When is the risk of a heart attack the highest? 

In the mornings, on Mondays, and after DST in spring.

In the mornings we wake up and get a sudden burst in cortisol and, although it’s not completely clear why that happens, it likely serves as a preparation for the daily stresses and high demands that modern living places on our bodies.  We also suddenly change position from lying into standing and moving around.

All of these stresses could each play a role in why the incidence of infarction and sudden cardiac death is the highest in the mornings. 

Mondays make the most dangerous days of the week. Working people are at the highest risk of having a heart attack on a Monday as that’s when they need to wake up early again after a weekend’s long slumber. As far as the data suggests, you could save your own life by sticking to a regular sleep/wake routine regardless of the day of the week. Then your body will not suffer these strong shifts in schedule. Also, make sure to get enough sleep during the week so you won’t feel the need to “catch up” on your days off.

Figure 1. Incidence of myocardial infarction (MI), sudden cardiac death (SCD), and ischemic stroke in the morning. Image source: Role of the circadian system in cardiovascular disease. S. Thosar, M. Butler, and S. Shea

Daylight Saving Time (DST), or more specifically shortening your night by one hour in spring, is another period when people around the world suffer from heart attacks and increasingly die in the morning. 

Every year, there’s a 24% increase in heart attack incidences in the week after DST change. Here Tuesdays are days with the highest infarction rate, they even come before Mondays. It seems that many people accumulate stress during the first day after DST and then on a Tuesday when waking up earlier continues, their heart simply fails.

Sleep disorders and cardiovascular health

Some sleep disorders can increase the risk factors for cardiovascular diseases such as insomnia, hypersomnia, obstructive sleep apnea (OSA), or restless leg syndrome

People having problems with too short and too long sleep (which is always the case in chronic insomnia and hypersomnia sufferers) have a higher risk of cardiovascular disease and heart attack. A study has shown that even if you have a genetic predisposition for infarction, a healthy sleep duration will mitigate the risk. The right amount of sleep for you depends on your age, sex, genetics, and health.

Obstructive sleep apnea is a breathing problem that causes snoring and an occasional stop in breathing. In order to not choke, people wake up and change their position. Restless leg syndrome (RLS) gives people an unpleasant sensation in legs urging them to move. RLS can cause insomnia and fragmented sleep.

All of these sleep disorders cause poor quality sleep and/or short sleep. For a healthy heart, a  healthy body and other benefits, you need sufficient, restorative sleep.

Additional resources

  1. How Sleep Deprivation Affects Your Heart. https://www.sleepfoundation.org/excessive-sleepiness/health-impact/how-sleep-deprivation-affects-your-heart
  2. Association of Sleep Duration and Quality With Subclinical Atherosclerosis. http://www.onlinejacc.org/content/73/2/134?_ga=2.117051904.70973726.1549031369-676897364.1549031369
  3. Role of the circadian system in cardiovascular disease. https://www.jci.org/articles/view/80590
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