Sleeping on your side, ideally with your head slightly elevated, promotes brain cleansing (the glymphatic system) and thus reduces brain fog and dark circles upon waking.

noli's read

The idea is based on neuroscience research showing that the glymphatic system, which clears metabolic waste from the brain, is much more active during sleep. Animal studies (notably published in the Journal of Neuroscience) have demonstrated that the lateral position is more effective for this drainage than dorsal or ventral positions. However, it is crucial to note that this evidence comes primarily from rodent models under anesthesia. While the mechanism is biologically plausible in humans, direct clinical data confirming that a simple sleeping position significantly reduces brain fog or physical appearance (dark circles) lack robustness. The advice is therefore an interesting extrapolation based on solid science concerning brain cleansing, but its concrete benefits for daily well-being are presented somewhat optimistically compared to current literature.

the sources

1. 1Xie L, Kang H, Xu Q, et al. 2013