Sleep apnea is a relatively common sleeping disorder. Two variants exist: obstructive sleep apnea (OSA) and central sleep apnea (CSA). OSA occurs when the upper airway becomes blocked during sleep and interferes with breathing. Meanwhile, CSA occurs when muscles and nerves are insufficiently activated for breathing while asleep, leading to pauses in airflow. An estimated 936 million adults globally have mild to severe OSA.
Mild cases of the condition may be treatable with lifestyle changes such as weight loss or quitting smoking. For moderate to severe OSA, surgery or devices that can open a blocked airway, such as continuous positive airway pressure (CPAP), may be recommended.
In the current study, researchers investigated the link between known or suspected OSA and dementia risk over 10 years among older individuals. To do so, they analyzed data from 18, 815 US-based men and women aged 50 years and over. All were dementia-free at the start of the study. Ultimately, 9% of women and 8% of men developed dementia, and 68% of men developed OSA alongside 31% of women.
After analyzing the data, the researchers found that known or suspected OSA was linked to a higher incidence of dementia between ages 60 and 84 years old in both men and women. They noted, however, that women with known or suspected OSA were more likely than men to receive a dementia diagnosis across all age groups and that while women were more likely to receive a dementia diagnosis as they aged, the opposite was true for men.
The precise reasons underlying the observed sex differences remain unknown. However, possible explanations exist. For example, moderate sleep apnea in women may be linked to a higher risk of cardiovascular disease and insomnia, both of which negatively affect cognition. Declining estrogen following menopause can also have an impact.
"This study design cannot fully prove that sleep apnea causes dementia -- that would likely require a randomized trial, over many years, to compare effects of sleep apnea treatment to the effects of no treatment," said co-author Ronald D. Chervin, M.D., M.S., director of the Division of Sleep Medicine in the Department of Neurology at University of Michigan Health, in a press release.
"As it may be a long time if ever until such a trial occurs, backward-looking analyses such as ours, within large databases, may be among the most informative for years to come. In the meantime, the results provide new evidence that clinicians and patients, when making decisions about testing for sleep apnea and treating it, should consider the possibility that untreated sleep apnea causes or exacerbates dementia,” he added.
Sources: Science Daily, Sleep Advances