As cognitive and neuroscience research has expanded in the last decade, many researchers have been questioning the impact of specific sleeping habits or routines on the brain. Memory recall, dream patterns, and different sleeping positions’ impact on the brain are just some aspects of a biological mystery scientists are trying to uncover. A study done in 2014 states that sleep is crucial to a number of brain functions, including how neurons communicate with each other. With a lack of sleep, we cannot form and maintain the pathways that the brain uses for learning new things and establishing memories. A subtle but interesting factor affecting sleep is sleeping position.

Different sleeping positions can influence sleep quality dramatically. Scientists investigated the effects of body position on cognitive outcomes, particularly short-term memory, and whether sleep quality moderates the effects of posture. Supine refers to lying flat on the back, while sitting or upright refers to being in a vertical seated or standing position. Twenty-two healthy young adults took part in two testing sessions. In each session, they did memory tests while in two different positions — lying down and sitting up. Physiological measures like heart rate indicated that lying down increased restful brain activity and sitting increased fight-or-flight brain activity. The research identified that reclining activated calm brain behavior, and sitting activated more alert behavior and fight-or-flight behavior. On the other hand, for people who already had worse quality sleep, reclining seemed to worsen their cognitive performance, perhaps because the reclined state decreased their ability to stay alert. Therefore, while posture can affect brain functioning, sleeping on your back does biomechanically support better overall sleep quality.

“The posture we sleep in—on our side, back, or stomach—affects not just comfort, but also what happens to our brains.”

When sleep quality is low, cognitive performance deteriorates when supine. However, poor sleep quality can be mediated by sitting upright. Upright posture may provide some added energetic benefits against cognitive impairments due to disturbed sleep. MRI imaging was able to show the efficiency of cerebrospinal and interstitial fluid exchange and waste disposal in the brain in rodents placed in different sleeping positions. The researchers noticed that waste clearance was maximized when the rodents were lying down on their sides. They then hypothesized that this phenomenon may relate to humans, as side sleeping is already the most common natural sleep position in humans. Therefore, human beings may have evolved to prefer side sleeping due to its optimization of the elimination pathways within our brains.The conclusions of these studies point to a few basic best practices for sleeping position to boost cognition. Firstly, sleeping on your lateral side is the best for your overall cognitive health, maximizing waste removal, thereby decreasing the risk of neurodegenerative diseases like Alzheimer’s. Secondly, sleeping on your front has consistently proved to be the worst for your cognitive health. However, for the most part, sleeping habits and their many effects on cognitive health still remain a mystery to neuroscientists, and more research has yet to be done. The posture we sleep in—on our side, back, or stomach—affects not just comfort, but also what happens to our brains. While evidence continues to evolve, studies like these remind us that this simple act of how we position ourselves at night may be, albeit a small contribution, an important piece in helping support brain health in the long term.