Obstructive sleep apnea (OSA) is a sleep disorder that causes the walls of the throat to relax and narrow, cutting off breathing temporarily during sleep. Previous studies have identified that this limits the oxygen available in the bloodstream reaching the brain. The researchers responsible for the current study believe that it’s this decline in oxygen that causes shrinking in the brain’s temporal lobes, resulting in memory loss.
“Between 30 and 50 percent of the risk for dementia is due to modifiable factors, such as depression, high blood pressure, obesity, and smoking. In recent years, researchers have recognized that various sleep disturbances are also risk factors for dementia. We wanted to look specifically at obstructive sleep apnea and its effects on the brain and cognitive abilities,” said Professor Sharon Naismith from the University of Sydney, the lead researcher on the study.
The study consisted of 83 people between the ages of 51 and 88 years old. The participants were selected because they had previously visited a doctor or medical practitioner with concerns about memory loss but had shown no signs of sleep apnea in the past. The participants were tested for memory loss and depression. They also underwent an MRI, so the researchers could measure the different parts of their brains.
Finally, they participated in a sleep lab, so their sleep patterns could be observed and any signs of OSA could be identified through a polysomnography, which measures brain activity, oxygen levels, heart rate, breathing, and movement.
Lower Oxygen Levels Related to Memory Loss
The results of the analysis showed that the participants with lower levels of oxygen in their blood during sleep were more likely to have thinner left and right temporal lobes. These are the areas in the brain most important in memory functions and most often affected by the onset of dementia. The researchers also found increased thickness in other parts of the brain of these participants, which they believe may be the brain responding to the lower oxygen levels with inflammation.
The participants with lower blood-oxygen levels and altered brain shape were more likely to show memory loss and the inability to learn new information. This is the first time a concrete association between the two has been shown.
The researchers believe that screening older patients for obstructive sleep apnea may be a way to identify dementia in its early stages and prevent the disease’s full development. “We chose to study this group because they are older and considered at risk of dementia. Our results suggest that we should be screening for OSA in older people. We should also be asking older patients attending sleep clinics about their memory and thinking skills, and carrying out tests where necessary,” said Naismith.
While there is still no cure for dementia, obstructive sleep apnea has effective treatment methods, which may prevent the development of dementia if they are implicated early on.
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- How dementia progresses: The 7 stages of dementia
- Mild cognitive impairment causes, risk factors, complications, and treatment