Getting too much sleep, or too little, may be bad for your heart, the results of a new study indicate.

According to the findings, people who get seven or eight hours of sleep per night have less stiffness in their arteries, which is associated with a lower risk of developing heart disease or suffering a stroke.

As part of the study, the sleep patterns of almost 1,800 people were assessed and based on this, the participants were divided into four groups:
-Normal (seven to eight hours sleep per night)
-Short sleep duration (six to seven hours per night)
-Very short sleep duration (less than six hours per night)
-Long sleep duration (more than eight hours per night).

The participants included people with no health conditions, as well as people with heart disease and cardiovascular risk factors. They ranged in age from 40 to 98, with an average age of 64.

The study found that even after known risk factors for heart disease and stroke were taken into account, those who slept for less than six hours, or more than eight hours per night, had a significantly higher risk of having a build-up of plague in their carotid arteries, compared to those who got seven or eight hours of sleep each night.

Plague build-ups can lead to atherosclerosis (hardening of the arteries).

In fact, those who slept for less than six hours per night had a 54% increased risk of having a plague build-up in their arteries, while those who got more than eight hours had a 39% increased risk.

"The message, based on our findings, is ‘sleep well, but not too well.' Getting too little sleep appears bad for your health, but too much seems to be harmful as well.

"Unlike other heart disease risk factors such as age or genetics, sleep habits can be adjusted, and even after taking into consideration the impact of established risk factors for atherosclerosis and cardiovascular diseases, for example age, gender, obesity, smoking, diabetes and high blood pressure, both short and long sleeping duration may act as additional risk factors," commented the study's lead author, consultant cardiologist, Dr Evangelos Oikonomou.

He acknowledged that the researchers "do not fully understand the relationship between sleep and cardiovascular health".

"Short sleep duration may be associated with increased cardiovascular risk factors, for example, unhealthy diet, stress, being overweight or greater alcohol consumption, whereas longer sleep duration may be associated with a less active lifestyle pattern and lower physical activity," he suggested.

He said that getting six to eight hours sleep per night appears to act as a "cardioprotective factor" among people. He called for more research in this area, particularly in relation to getting too much sleep, as this has not been studied as much as getting too little.

Details of these findings are to be presented at the American College of Cardiology's Annual Scientific Session Together with World Congress of Cardiology (ACC.20/WCC), which is due to be held virtually in late March, due to COVID-19 (coronavirus).