How does sleeping chest-side down hurt the spine?

Question

I do not know the correct English term for the position, so I will just refer it to as "chest-side down". The following CNN page seem to call it the "stomach position", and they say it is the worst position to sleep.

They have listed the shortcomings of that position, but there is no detailed explanation. I do not feel any pain when I sleep chest-side down other than pain on my neck, but this is only because I have to turn my face to one side, and this can be fixed if I buy a special pillow (something used at a massage shop).

Is it really true that it causes back pain? We are mammals and almost all mammals live and sleep chest-side down. Dogs, for example, seem to love to rest their chest and head laid down on the floor. Do we have some special spines that need to be rested chest-side up, unlike other mammals?

And secondly, how does it cause more wrinkles than sleeping chest-side up?

Source: http://edition.cnn.com/2011/HEALTH/04/19/healthiest.sleep.position/

Bad for: Avoiding neck and back pain, minimizing wrinkles

The scoop: "Stomach-sleeping makes it difficult to maintain a neutral position with your spine," Shannon explains. What's more, the pose puts pressure on joints and muscles, which can irritate nerves and lead to pain, numbness, and tingling.

Answer 1

I do not feel any pain when I sleep chest-side down other than pain on my neck, but this is only because I have to turn my face to one side, and this can be fixed if I buy a special pillow (something used at a massage shop).

In any medical topic, you shouldn't assume that a habit is healthy just because it doesn't immediately cause pain. If you feel pain in the neck muscles this might hurt your posture and in turn, hurt your back.

We are mammals and almost all mammals live and sleep chest-side down. Dogs, for example, seem to love to rest their chest and head laid down on the floor.

I think the way the dogs sleep depends more on their personality rather than anatomy. Many dogs do sleep on the side. If you look at our closer relatives - chimps they typically sleep on the side.

Generally, the human spine suffers a lot from bad posture. Asymmetrical weight distributions, prolonged stretch, prolonged contractions can cause the vertebrae to wear down. A problem in sleeping prone is the fact that you need to contract lower back muscles and neck muscles (regardless if your face is pointing sideways or down). This causes tension which can sometimes be felt the day later. However, the main problem here is that long-term sleeping in that position will reflect on your posture and cause additional wear and tear on the back and possibly cumulative trauma disorders.

I recommend you this video for understanding how muscles work during sleep.

There are many reasons to sleep on the side, but this goes beyond the scope of the question. If you want to sleep on the stomach, you can, but you should make sure that you take care of your posture and don't overexert your lumbar and neck muscles.