Getting too little sleep is a well known health hazard, raising the risk of a host of conditions, including obesity and heart disease.
But, now a team of scientists have warned getting too much sleep can also be bad for the heart.
Their findings reveal a fine line between a healthy night's sleep and shut eye habits that could increase the risk of early death.
Anything less than four hours sleep is deemed detrimental to a person's cardiovascular health.
A lack of sleep is known to be linked to stress responses that increase heart rate, blood pressure and the secretion of the hormone adrenaline - all risk facts for heart disease.