Is sleeping on your left side safe?

Sleeping on Left Side Safety

Sleeping on the left side is generally safe for adults but is not recommended for infants under 1 year of age due to increased risk of SIDS. For adults, left-side sleeping may even provide certain benefits for specific conditions.

Safety for Infants (Under 1 Year)

The American Academy of Pediatrics (AAP) is very clear in their recommendations regarding infant sleep positions:

• Infants should be placed exclusively on their backs (supine position) for every sleep period until 1 year of age 1
• Side sleeping (including left side) is not safe for infants and is not advised 1
• The risk of SIDS associated with side sleeping is similar in magnitude to prone (stomach) sleeping, with odds ratios of 2.0 and 2.6 respectively 1
• Side sleeping is inherently unstable, with a significantly higher probability of an infant rolling to the prone position 1
• The risk is exceptionally high for infants who are placed on their side and found on their stomach (OR: 8.7) 1, 2

Why Side Sleeping is Dangerous for Infants

Side sleeping increases SIDS risk through multiple mechanisms:

• Increased risk of rebreathing expired gases, leading to hypercapnia and hypoxia 1
• Altered autonomic control of the cardiovascular system 1
• Inherent instability of the position, increasing likelihood of rolling to prone position 1, 2

Safety for Adults

For adults, sleeping on the left side is generally safe and may offer specific benefits:

Potential Benefits of Left-Side Sleeping for Adults

1. Gastroesophageal Reflux Disease (GERD):

   • Left-side sleeping significantly reduces esophageal acid exposure compared to right-side, supine, or even elevated positions 3
   • A randomized controlled trial found that sleeping on the left side with head/torso elevated resulted in significantly less esophageal acid exposure than other positions 3
   • Another double-blind randomized trial showed that promoting left-side sleeping using a positional therapy device effectively alleviated nocturnal reflux symptoms 4

2. Sleep Apnea:

   • Right-side sleeping may be preferable for sleep apnea patients, as it's associated with lower apnea-hypopnea index (AHI) compared to left-side sleeping 5
   • In patients with moderate to severe OSA, right-side sleeping decreased the frequency of obstructive respiratory events 5

Potential Concerns for Left-Side Sleeping in Adults

1. Heart Failure Patients:

   • Heart failure patients often prefer right-side sleeping and may experience increased dyspnea when lying on the left side 6
   • Echocardiographic parameters like LVOT TVI and TAPSE (measures of cardiac function) were higher in right-side position compared to left-side or supine positions in dilated cardiomyopathy patients 6

2. Theoretical Cancer Risk:

   • One controversial study suggested a potential link between right-side sleeping and left-sided breast cancer/melanoma due to electromagnetic field exposure from mattress springs 7, but this remains highly speculative and lacks mainstream scientific acceptance

Clinical Decision Making

For determining optimal sleep position:

1. For infants under 1 year:

   • Always place on back (supine) for every sleep
   • Never place on side or stomach
   • Once infants can roll from supine to prone and back again, they can remain in the position they assume 1

2. For adults with GERD:

   • Left-side sleeping is preferable, especially with head/torso elevation 3, 4

3. For adults with heart failure:

   • Right-side sleeping may be more comfortable and provide better hemodynamics 6

4. For adults with sleep apnea:

   • Right-side sleeping may reduce apneic events 5

5. For adults without specific conditions:

   • Either side is generally safe
   • Personal comfort should guide position choice

Common Pitfalls and Caveats

• For infants: The most dangerous pitfall is placing infants on their side thinking it's a safe compromise between back and stomach sleeping - it is not 1
• For adults with multiple conditions: When conditions conflict (e.g., GERD favoring left-side but heart failure favoring right-side), prioritize the more symptomatic or severe condition
• For pregnant women: Left-side sleeping is often recommended in late pregnancy to improve maternal cardiac output and fetal blood flow, though this wasn't specifically addressed in the provided evidence

Remember that for infants, back sleeping is the only safe option until 1 year of age, while adults generally have more flexibility in choosing sleep positions based on their specific health conditions and comfort.