The exact definition for a normal BMI varies somewhat, but anything over 30 is fairly well recognized as being overweight. Very heavy people will commonly have BMIs up around 40 or so. Alcohol is known to worsen sleep apnea. The muscles of the upper airway have been shown to lose some of their motor activity after consumption of alcohol. Individuals with sleep apnea should therefore have no more than a small drink before bedtime.
Gravity causes the base of the tongue to fall back and obstruct the airway.
These usually are not effective in actual practice. As with alcohol, certain medications like narcotic pain relievers and barbituates are generally felt to worsen OSA, so these should be avoided. Sleep apnea is usually worsened with nasal obstruction, so any medicine that improves nasal airflow may be helpful. Antihistamines such as Claritin or Allegra may be useful if allergies are present. Sleep apnea is worse with certain medical conditions such as hypothyroidism, and medical treatment of this disorder will therefore improve the apnea.