Because their TEETH ARE MISALIGNED AND THEY USUALLY POSSESS LONG TONGUE. Respiratory illness is common in people who have down syndrome and their unique airway anatomical factors makes airway management difficult during respiratory distress. For instance, they have narrower upper airway and smaller trachea.
I have a bad habit of chewing on my finger nails
Organisms will adapt to their environment in order to survive. They will do whatever it takes to survive.