How a blood clot affects the body is usually determined by its location, but it generally tends to be harmless as long as it doesn't move.

Most blood clots usually form within the veins of the leg, pelvis and sometimes the arms, which is called deep vein thrombosis.

Certain sleeping positions can be conducive to the formation of dangerous clots.

The body usually lies horizontally on the bed, so there is rarely enough gradient influence on the blood flow in the limb.

However, when one sleeps upright, problems can occur if blood flow is obstructed.

Harvard Health writes: "Sleeping sitting up on an incline can in some cases increase the risk of deep vein thrombosis."

A blood clot in a limb can occur if your arms or legs are both bent without movement for hours.

However, sleeping upright is not the only sleeping position with health risks.

According to experts at the Mayo Clinic, sleeping on your back can cause the tongue and jaw to hang down, crowding the airway.

This can set the stage for sleep apnea, which in turn can lead to serious problems involving the heart.

The health body adds: "Obstructive sleep apnea can also increase the risk of recurrent heart attack, stroke and abnormal heart rhythms."

There is some evidence that sleeping on the left side of the body can also affect the organ's electrical signals.