Nasal breathing.

Breathing through your nose can help filter out allergens, pathogens and dust, moisture is collected and trapped in the nostrils preventing it going down in to the lungs . Nose breathing helps to defend against infections and allergies

When you breathe through your nose, your sinuses naturally produce a gas called nitric oxide. As nitric oxide flows from the nasal sinuses to the lungs and into the blood ,it is reputed to reduce blood pressure as nitric oxide gas can widen blood vessels, helping to improve blood flow.

In this study, with 30 participants with mild obstructive sleep apnea who tended to breathe through their mouths while sleeping, researchers found that they snored less severely, on average, when they wore a patch over their mouths than they did when they didn’t.

https://pubmed.ncbi.nlm.nih.gov/25450408/

 The most common type of sleep apnea is known as obstructive sleep apnea. People who have it experience potentially dangerous pauses in their breathing while asleep, which can occur dozens or even hundreds of times a night, causing them to wake up or snore loudly as they struggle to breathe. These intermittent gaps in breathing are known as apnea episodes and they occur when your airway collapses in on itself, preventing air from reaching your lungs.

Obstructive sleep apnea increases your risk of a host of metabolic diseases. 

This sets off a cascade of problems:

• When breathing stops, oxygen levels plunge, which activates the sympathetic nervous system that controls the fight or flight response. 
• Adrenaline levels rise. 
• Heart rate increases. 
• Blood pressure rises, constricting blood vessels. 
• Snoring can occur as your body struggles to pull in oxygen.