In the study, researchers analyzed the patterns of low blood oxygenation during sleep and the relation to heart-related deaths in 2,840 men in their 70s and early 80s. The study was led by Associate Professor Dominik Linz and Associate Professor Mathias Baumert of the University of Adelaide's Medical School and School of Electrical and Electronic Engineering.
Normally, a healthy person has a 95 to 100 percent saturation during the day. This slightly declines during sleep because of shallower breathing. However, when a person has an oxygen saturation below 90 percent, it is considered low resulting in hypoxia where oxygen flow to the body is restricted.
The results showed that when the men had 12 or more minutes of sleep at low oxygen saturation below 90 percent, their risk of heart-related death increased by 59 percent. Moreover, Baumert explained that about 20 percent of the time that oxygen saturation was lower than 90 percent could not be attributed to episodic declines traditionally associated with sleep-disordered breathing or sleep apnea.
Sleep apnea is a condition in which a person experiences pauses in breathing five to 30 times every hour or more during sleep. As a result, the sleeper wakes up as he or she gasps for air, preventing restful sleep. It is also associated with high blood pressure, arrhythmia, stroke, and heart failure. It is a common problem and affects one in five adults.
The findings indicated that poor blood oxygenation during sleep is an indicator of heart-related death in older men. These also suggested that reduced blood oxygenation cannot be attributed to episodic drops in oxygen alone. Linz said that understanding the underlying causes of low oxygen saturation during sleep is vital in helping to prevent deaths. Screening for and treatment of risk factors aside from sleep-disordered breathing and obesity may also help reduce nocturnal hypoxia in people.
More on hypoxia
Hypoxia is defined as the deprivation of oxygen to the brain. There are four main causes of hypoxia: No blood supply to the brain; insufficient blood supply to the brain; no oxygen in the blood; and insufficient oxygen in the blood.
Injuries and illnesses can also cause hypoxia. These include allergies, allergic reactions that lead to anaphylactic shock, carbon monoxide poisoning, choking, heart attack or stroke, hyperventilation, severe cases of asthma, smoke inhalation, strangulation or smothering, traveling to high altitudes, and very low blood pressure. (Related: Living high, but feeling low? Study says that living in high-altitude areas increases your risk of depression.)
People experiencing hypoxia may feel like they cannot breathe, find it hard to catch their breath, or experience a rapid heart rate as the heart beats faster as an attempt to supply the brain with blood. Less severe oxygen deprivation can cause subtler and more gradual symptoms. In addition, some people who experience hypoxia may lose their ability to talk.
For more information on the link between poor sleep and death caused by heart disease, visit HeartDisease.news.
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