A team led by Dr. Yoon Chang-ho, Professor of Neurology at Seoul National University Bundang Hospital (SNUBH), announced the effects of long-term sleep apnea on the brain and cognitive function of adults. This was the world’s first large-scale study of its kind, and the results are expected to be used to devise policies for early detection and treatment of sleep apnea.
Sleep apnea is a sleep disorder in which breathing stops for more than 10 seconds or the narrowing of the upper airway occurs frequently during sleep, interfering with breathing. It lowers the quality of sleep, resulting in fatigue and poor concentration when awake.
The problem is that sleep apnea occurs during sleep, making it difficult for an affected individual to recognize it. If it is left untreated for an extended period of time, it not only leads to dementia and cognitive impairment but can also cause cardiovascular diseases such as hypertension and stroke in severe cases. Thus, early diagnosis and treatment are crucial.
However, most studies on sleep apnea have had a short follow-up or observation period or have been carried out with a small number of subjects. As such, there had not been any studies that revealed the effect of prolonged sleep apnea on the affected individual.
Accordingly, Professor Yoon’s team initiated a study to understand the effects of sleep apnea on the brain structure and cognitive function of adults through a long-term, large-scale follow-up. The study was conducted with 1,110 adults, who were divided into a normal group (negative in the 1st and 2nd tests), sleep apnea improvement group (positive in the 1st test and negative in the 2nd test), sleep apnea onset group (negative in the 1st test and positive in the 2nd test), and persistent sleep apnea group (positive in the 1st and 2nd tests). Their brain-MRI images and neurocognitive test results were compared and analyzed for two four-year periods: 1st analysis period (2011 to 2014) and 2nd analysis period (2015 to 2018).
Results established that damage was observed in the brain regions related to concentration and visual information processing in the sleep apnea onset group, while in the improvement group, the damaged visual memory pathway was found to have been restored. In the persistent sleep apnea group, brain damage related to visual memory was found, and these changes were more pronounced in men over 60 years of age.
In the case of the improvement group, the visual memory pathway (yellow) had been restored, whereas brain damage in the visual memory-related area (blue) was observed in the onset group and the persistent group.
According to the results of this study, if sleep apnea is not detected early, it may lead to reduced brain function, and if left untreated, it is expected to cause cognitive impairment such as dementia. Also, although the severity of apnea in the onset group was mostly mild, cognitive decline and brain damage were observed. This suggests the need to treat and manage not just severe sleep apnea but also mild cases.
This study has great academic significance as it is the world’s first large-scale population study that entailed long-term observation, revealing the effects of sleep apnea on the brain function and white matter. Furthermore, it is expected to help develop policies for early detection and treatment of sleep apnea.
“Through this study, we were able to discover that prognosis is good if sleep apnea is diagnosed and treated early,” said Dr. Yoon, the corresponding author of the study. He added, “In a rapidly aging society, aggressive medical treatment and care are necessary to reduce the incidence of dementia and cognitive impairment.”
This research, supported by the Korea Disease Control and Prevention Agency, was jointly carried out by Dr. Shin Chol, Professor of Pulmonology at Korea University Ansan Hospital, and Professor Robert Thomas from Harvard Medical School. The results were published in JAMA Network Open, issued by the American Medical Association.