Nasal breathing has been shown to have various physiological benefits, including effects on heart rate variability (HRV), blood pressure, cortisol levels, and sleep quality. Here's a detailed look at the scientific evidence supporting these effects:

Heart Rate Variability (HRV)

Nasal breathing has been associated with an increase in highfrequency (HF) contributions to HRV, indicating enhanced parasympathetic activity, which is responsible for the body's "rest and digest" functions. A study found that nasal breathing resulted in a higher HF contribution to HRV compared to oral breathing (59 ± 19% vs. 52 ± 21%, P = 0.04). This suggests that nasal breathing can enhance autonomic balance by increasing parasympathetic activity and reducing sympathetic activity, as indicated by a lower lowfrequency to highfrequency (LF/HF) ratio during nasal breathing (0.9 ± 0.8 vs. 1.2 ± 0.9, P = 0.04).

Blood Pressure

Nasal breathing has been shown to lower diastolic blood pressure. A study highlighted that acute nasal breathing lowers diastolic blood pressure in young adults[9]. This effect is attributed to the enhanced parasympathetic activity and possibly improved airway resistance during nasal breathing. Lower diastolic blood pressure is beneficial as it reduces the strain on the heart and arteries, potentially lowering the risk of cardiovascular diseases.

Sleep Quality

Nasal breathing significantly impacts sleep quality by reducing upper airway resistance and the severity of obstructive sleep apnea (OSA). Studies have shown that nasal breathing during sleep significantly lowers upper airway resistance compared to oral breathing[1]. This reduction in resistance can lead to fewer sleep disruptions and a lower incidence of sleep apnea, contributing to better overall sleep quality. Additionally, nasal breathing is associated with a reduced frequency of obstructive sleep events like apneas and hypopneas compared to oral breathing[1].

In summary, nasal breathing enhances HRV by increasing parasympathetic activity, lowers diastolic blood pressure, potentially helps in managing cortisol levels through improved stress response, and improves sleep quality by reducing upper airway resistance and the severity of sleep apnea. These benefits make nasal breathing a valuable practice for overall physiological health and wellbeing[1][9].

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