Apnoea (also apnea) is a condition in which breathing stops for longer than 10 seconds more than 30 times a night. The most severe forms of apnoea also involve heavy snoring. The brain eventually detects the lack of oxygen and the person wakes up, for a few seconds at least, and starts breathing again. Apnoea exhausts the heart and lungs, is directly linked to cardiovascular problems, including high blood pressure, and if not treated can cause sudden death, often by stroke. The suspected cause is a drop in the blood flow to the brain as breathing stops, followed by a build-up of blood pressure and an increase in heart rate as the body wakes and struggles for air. The drop in pressure ranges from 14% in mild cases of apnoea to 80% in the severe forms that include snoring.
The constant interruptions to sleep result in extreme daytime drowsiness, and sometimes in narcolepsy.
Apnoea is common in chronic snorers. It is more common in overweight people and this relationship may account for its increasing incidence. The incidence of stroke is up to 40% higher in apnoea victims than in the normal population.
In premenopausal women, 100% of those with sleep apnoea were also obese, compared with only 40% of the men who had sleep apnoea and were also obese. Postmenopausal women who were taking hormone replacement therapy have a reduced risk of sleep apnea.