Snoring is the sound produced while sleeping due to partial upper airway obstruction. Snoring is caused by high-frequency vibration of the soft palate as a result of narrowing of the upper airway.
Basically anything that causes upper airway obstruction:
Being overweight
Excessive neck thickness
Macroglossia (large tongue)
Micrognathia (jaw being narrower and smaller than normal)
Retrognathia (the lower jaw being positioned further back)
Nasal polyposis
Adenoid hypertrophy
Drooping uvula (small tongue)
Hypertrophic tonsils (extremely large tonsils)
Septum deviation
Concha hypertrophy
Hypothyroidism
Cessation of breathing during sleep
Daytime sleepiness
Memory and reasoning disorder
Concentration disorder
Decreased school and work performance
Morning headaches