Doctors estimate that about 18 million Americans suffer from sleep apnea, with the condition being more common for men and for those over 40.

More information on the condition's causes symptoms and possible treatments is available from:

* The National Heart Lung and Blood Institute of the National Institutes of Health

* The NIH's National Center on Sleep Disorders Research

* MedlinePlus

* The American Sleep Apnea Association

* American Academy of Family Physicians

* The Mayo Clinic