When they close the airway completely this is known as obstructive sleep apnea, which can lower the blood oxygen level and cause significant health problems.
But all of this is minor compared to the sleep deprivation experienced by the person who lies in bed next to you, tossing and turning and trying to resist the temptation to jab you in your ribs or stuff a pillow over your face.
snoring cap
My 2nd daughter at 10 months,( first Easter) failure to thrive then again at 3( twice in 2 months).