How thick our pillow should be?

To avoid back pain we are often advised to sleep on hard mattresses and use thin pillow approximately one to two inches thick, so that natural alignments of individual vertebrae is not disturbed and they do not come together due to unnecessary bending of spine and compress each other. Anyhow if two vertebrae compress each other, they will constrict various nerves coming out of them which may usually lead to pain in the back or in some other parts of the body. Therefore to avoid back pain we must keep our spinal cord in natural and proper alignment and use a thin pillow. The following diagram shows the correct position of our spinal cord.

So it is required that our spinal cord should remain in its natural position and this is to be maintained even during our sleep. Thin pillow may be useful when we sleep straight on our back and it de-stress us up to large extent. This type of sleeping pose is given in the following pictorial.

Here a question arises that how long we can sleep in this position i.e. on our back? This position remains for few minutes only. After that we either turn right or left. It is astro-physico requirement due to nostril dominance or swar/naadi uday which is controlled by the movement of sun and moon. Our body has three naadis i.e. Surya Nadi or Ida, Chandra Naadi or Pingala and Sushumna Nadi. The 'Ida' is associated with left nostril. When we inhale and exhale dominantly with left nostril the 'Ida' is active. In contrast to this when breathing is dominant by right nostril the 'Pingala' is active. And when we inhale and exhale equally by both nostrils, the Sushumna Naadi is said to be active and dominant. This dominance changes alternatively after a definite period and is controlled by the time, day and position of sun and moon. The position remains same in the night even when we sleep. So it is mandatory to inhale dominantly by one nostril at a time. The equal inhaling by both nostrils is exceptional and is required when we practice different stages of yoga like asanas, pranayam, dhyana, samadhi etc.

       Our body is made in such a fashion that when we sleep on our left, the left nostril is blocked and we start inhaling with right nostril. Likewise when we sleep on right side the right nostril is blocked and left nostril is open for breathing. It means that a particular nostril is blocked on the side which we sleep. But when we sleep on our back both nostrils breathe equally. This pose in yoga parlance is termed as shavasana i.e. pose in which dead body is kept. So when we sleep straight on our back we are in shavasana i.e. pose for dead body which is not required at all.

        So it is our compulsion to sleep either left or right. If we sleep on either side without pillow or with thin pillow initially our hand will support our skull for a while and later on hand is removed from the position and our head bends down one side. This position continues as long as we sleep and an undesirable stress occurs in spinal cord as depicted in the following pictorial. 

          

           This perpetual continuos bending of neck during sleep ultimately lead neck vertebrae to compress each other and constricts nerves coming out of them. The continuous sleeping in such manner for a long time will definitely lead to deformities in spinal cord. This is one of the root cause of neck pain or back pain.

           When it is mandatory and clear to us that we have to sleep either our left side or right side, therefore we should do all possible efforts to keep our neck vertebrae straight during sleep. During sleep the position of our spinal cord is supposed to be like this.

            Here we see that person sleeping is using a pillow which is equally thick to his shoulder.To attain this position the thickness of our pillow should be equal to the length of our shoulder.  This will keep our skull and cervical vertebrae allinged with the rest of the body. The individual vertebra will not bend and compress one another, irrespective of any side we sleep and one major reason for back pain is avoided.

           Therefore answer to the question is that, ‘our pilloe should be as thick as the length of our shoulder’.