CHICAGO (AP) _ A disorder that causes breathing lapses while sleeping is linked to a gene variation associated with Alzheimer's disease and cardiovascular problems, a study has found.
An estimated 18 million Americans suffer from sleep apnea, characterized by snoring and brief breathing lapses during sleep. These lapses can occur when the throat muscles and tongue relax too much, blocking the airway.
Sleep apnea is mostly hereditary. A new study, led by Dr. Hiroshi Kadotani of Stanford University's psychiatry and behavioral sciences department, suggests that 8 percent of it could be due to the gene variation called apolipoprotein E-4.
Compared with people without the trait, study participants with the E-4 variation faced almost double the risk of having sleep apnea, the authors reported in Wednesday's Journal of the American Medical Association.
The results come from an ongoing sleep disorders study involving 791 middle-aged adults. Of the 222 participants with the E-4 variation, 12 percent had moderate to severe apnea, compared with 7 percent of participants without the variation.
The authors said sleep apnea may interact with the E-4 trait to impair cognition. They noted that sleep apnea ``induces sleepiness and may damage the brain irreversibly through long-term'' low levels of oxygen in the blood.
The study does not necessarily imply that all adults with sleep apnea face an increased risk of Alzheimer's and cardiovascular disease, even though the E-4 trait has also been linked to those ailments.