Sleeping on your side may help to remove waste products in the brain
sciencealert.com
sciencealert.com
Oh come on. Medical studies I can understand animal testing having some relevance, but this study on rodents and applying the results to humans without a massive disclaimer? That's a step too far.
I tried to find the "X year", a placeholder that was probably forgotten by the OP, and the source of the survey page contains the following snippet
<meta name="DC.date.modified" content="2014-08-12T08:38:03+00:00"/>
<meta name="DC.date.created" content="2014-08-11T14:42:58+00:00"/>