During sleep the throat narrows due to a reduction in muscle tone. Snoring is simply the vibratory noise generated by the back of the relaxed tongue, palate and throat. Further narrowing produces louder snoring but also laboured inspiration (breathing in). Extreme narrowing can cause complete airflow obstruction otherwise known as obstructive sleep apnoea.
There comes a point where the increased inspiratory effort is sensed by the sleeping brain and a transient arousal is provoked (brief awakening to breathe before returning to sleep). A few of these arousals do not really matter.
However, when there are many (sometimes hundreds), sleep becomes seriously fragmented, resulting in daytime symptoms of excessive sleepiness. Snoring and sleep apnoea are part of a spectrum extending from ‘benign’ or ‘simple’ snoring with no sleep disturbance, through to obstructive sleep apnoea with severe daytime sleepiness symptoms and the physiological consequences of recurrent asphyxia (insufficient oxygen).