Lying on your left side, is it really that sinister?
What IS the best sleeping position?
[Definition of sinister: 1. of, relating to, or situated to the left or on the left side of something; 2. of ill omen by reason of being on the left ]
Recently, I found myself in a debate on which are the best sleeping positions. After a lengthy back and forth, I came to the realization — it depends.
Against Left Side :
The sinister aspect of left side sleep came up when I researched the origins of atrial fibrillation episodes, described in a past newsletter:
It was reported by patients to be a potential trigger, enough so, that it was included as a research variable in an ambulatory cardiac monitoring study. Subjects self-reported when they thought they were experiencing afib and what preceded the event. However the study found that only alcohol consistently, and dose dependently, triggered fibrillation. Left-sided position was not a factor.
But something about the turning onto that side, caused anxiety or at least arousal enough for the subject to notice and suspect it. The ‘common sense’ explanations included compressed and crowded space around the heart. Perhaps they somehow ‘tickled’ their cardiac sympathetic ganglion? [http://vanat.cvm.umn.edu/ans/pages/SympDivAll.html ]
Another mystery involves a left sided organ - the spleen. There is a real life phenomenon that is called Wandering Spleen. Sometimes congenital and sometimes acquired later in life, e.g., connective tissue disease or pregnancy, the ligaments holding the organ become lax. Symptoms that manifest depend upon where the spleen migrates to and whether the blood supply gets twisted and compromised. Left sided lying may affect where that spleen does lay.
For Left Side:
The biggest argument posed for left sided sleeping is to reduce acid reflux. Some believe that sleeping on the right side causes the muscles of the esophagus and stomach to relax too much, leading to acid leakage into the esophagus, causing heartburn. Others believe that sleeping on the left side positions the opening of the esophagus above the stomach, on an upward angle, thus preventing acid from reaching it.
The left-siders also promulgate the theory that lymph drains best when sleeping on that side. Lymphatic ducts empty lymph fluid into the venous system. The two lymphatic ducts of the body are the right lymphatic duct and the thoracic duct, on the left. The thoracic duct is the larger of the two and responsible for lymph drainage from the entire body except for the right sides of the head and neck, the right side of the thorax, and the right upper extremity. The thoracic duct terminates in the left internal jugular vein or the subclavian vein.
General advice to pregnant moms, based on ‘common sense’ was to sleep on the left side to keep the uterus off of their vena cava, and thus prevent interference with the venous return to the right heart. However, when clinical studies actually evaluated that ‘position’. …
Both Sides now:
Pregnancy studies examined the sleeping position chosen at initiation of slumber [associated with longest time during night]. Meta-analysis of multiple studies concluded that sleeping on either side is okay, just not supine. Increased risk of stillbirth emerged when the mom slept on her back in the last trimester, especially the week before childbirth.
Sleeping on your belly, pregnant or not, requires a commitment to a side of face on the pillow in order to allow free breathing. So that is a kinda both-sides-now position, too.
Another is the drainage of the brain’s glymphatics. I described the newly discovered lymphatic system in an earlier newsletter, and linked to cool videos of pulsating flow correlated with heart beats and breaths.
Their drainage still needs gravity though, so sleep should be on both sides to clear both brain hemispheres. Otherwise one side will clog up - and increase the risks for Alzheimer’s or Parkinson’s diseases.
Well dear reader, I have carefully experimented and evaluated each position and can confidently conclude… I am definately a right-sider!
What side are you on?
REFERENCES
Atrial fibrillation commonly triggered by alcohol consumption https://www.openaccessgovernment.org/alcohol-consumption-associated-with-heart-condition/124902/
GM Marcus et al. 2021 Individualized Studies of Triggers of Paroxysmal Atrial Fibrillation: The I-STOP-AFib Randomized Clinical Trial https://jamanetwork.com/journals/jamacardiology/article-abstract/278619
RS Cronin et al. 2019 An Individual Participant Data Meta-analysis of Maternal Going-to-Sleep Position, Interactions with Fetal Vulnerability, and the Risk of Late Stillbirth https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(19)30054-9/fulltext
RS Cronin et al. Survey of maternal sleep practices in late pregnancy in a multi-ethnic sample in South Auckland, New Zealand. BMC Pregnancy and Childbirth (2017) 17:190 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5474014/pdf/12884_2017_Article_1378.pdf
Shabir Ahmad Qazi et al. Wandering spleen Saudi J Gastroenterol 2004;10:1-7 https://www.saudijgastro.com/text.asp?2004/10/1/1/33345
https://rarediseases.org/rare-diseases/wandering-spleen/