What science says about sleeping on your (left) side

Sleep Matters Perth Blog

A common advice on self-help, health, and fitness blogs is to sleep on the left side. Of the variety of reasons provided, not many appear logically sound or scientifically accurate. As a result, it is advice usually dismissed as just another irrelevant urban legend.

Science, however, has been out verifying the claims. Several studies support the benefits of sleeping on one’s left side (ie, with the right side up).

Gastroenterological benefits of Left side sleeping position

Sleeping on the left side is sometimes advised as a preventative measure against acid reflux while sleeping, and even as a symptomatic remedy for GERD (Gastroesophageal reflux disease).

Gastroesophageal Reflux (GER) occurs when stomach juices escape from the sphincter (the sphincter keeps the stomach sealed and separate from the oesophagus). When functioning well, the sphincter opens for a small amount of time after swallowing to allow food/liquid inside, and occasionally to regurgitate the contents of the stomach when we’re unwell. Higher incidence of GER can cause inflammation of the food pipe and other uncomfortable symptoms.

Research cited by The Jama Network, (case controlled studies) shows an improvement in GERD related to sleeping on the left side, elevation in HOB (Head of Bed) and weight loss.

The National Center for Biotechnology Information (USA) found  differences in stomach reflux in 20 subjects favouring sleeping on the left side. Another study available via the same source informs us about a positive correlation between sleeping on the right side and higher incidence of gastroesophageal reflux as compared to sleeping on the left side, on the back or on the stomach.

The relaxations of the lower esophagal sphincter are kept a track of through LES manometry. A study on NCBI details higher incidence of GER episodes with sleeping on the right side as compared to the right side, noting more TLESRs or relaxation in the sphincter as well as more number of reflux episodes.

It is thus easy to establish that sleeping on the right side does cause higher incidence of stomach reflux, and the converse is true as well.

Benefits to Brain from Lateral Decubitus Position in Sleep

The Journal of Neuroscience published a study in August 2015 found an improvement in the Glymphatic system (the system that clears waste from the brain) when rats slept on their side or back compared to in an upright position.[MJR1]  The study even goes on to propose that sleeping on the side evolved to optimise removal on waste while sleeping. While this study isn’t suggesting that sleeping on the left is better than sleeping on the right, it does suggest side sleeping is better than sleeping on our backs.

Other benefits of sleeping on the side

Other benefits commonly attributed to sleeping on the side include helping people with obstructive sleep apnea, snoring and neck pain. It is proposed that sleeping on the side helps keep the air pathway clear while sleeping, which can otherwise be at risk of the tongue sliding back while sleeping. This also helps reduce snoring. Sleeping on the side can also be helpful in keeping the spine in proper alignment, commonly attributed to a better sleep.

Guest blog by Jenna Jamieson

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