The Connection Between Sleep Apnea and Alzheimer’s Disease
Understanding the link between obstructive sleep apnea and Alzheimer’s disease begins with understanding the role sleep plays in our cognitive health. Years of studies have confirmed that the brain, once thought to be passive during sleep, is actually very active and dependent on sleep to carry out important functions. Comparing the characteristics of obstructive sleep apnea and Alzheimer’s disease and their connection to impaired sleep further substantiates what researchers are continuing to discover; that there is a definite correlation between these diseases.
According to the Alzheimer’s Association, over 6 million Americans have Alzheimer’s disease, with the majority being over 65 years of age. Alzheimer’s is a degenerative brain disease caused by cell damage and the resulting changes in the brain. Often used interchangeably with Alzheimer’s disease, dementia is a broader term used to describe the symptoms of cognitive decline, such as loss of memory, and compromised reasoning and learning skills. Alzheimer’s disease accounts for 60-80% of all dementia cases and is a cause of dementia. The actual cause of Alzheimer’s disease is believed to be the build-up of proteins in and around brain cells. The particular protein known as amyloid and its associated plaque are hallmarks of damage seen in Alzheimer’s brain studies. In addition to the development of plaque in the brain, another Alzheimer’s characteristic is brain atrophy. The hippocampus, the part of the brain associated with memories, actually decreases in size as the disease progresses.
Studies at Johns Hopkins University School of Medicine confirm one of sleep’s key roles, which is to recalibrate brain cells that are responsible for learning and memory. This recalibration allows a person to recall what they’ve learned and apply it afterward. Alzheimer’s patients often have interruptions in the circadian rhythm system, which prevents deep, prolonged sleep. Prevention Magazine examined the relationship between Alzheimer’s patients and sleep, wondering if sleep problems lead to Alzheimer’s or if Alzheimer’s patients have inherent sleep problems, referring to this as a bidirectional relationship.
According to the American Academy of Sleep Medicine, over 30 million people in the US suffer from Obstructive Sleep Apnea (OSA), the most prevalent type of sleep apnea. OSA is characterized by frequent, repeated interruptions in breathing during sleep. While it is commonly associated with nighttime snoring and daytime sleepiness, new research shows that sleep apnea’s effect on cognitive function may actually lead to Alzheimer’s disease. New studies published in Medical News Today confirm the link between Alzheimer’s disease and sleep apnea. Post mortem brain studies from OSA patients reveal a reduction in the size of the hippocampus. In addition, studies from RMIT University in Australia, published in the journal Sleep, found the first evidence of amyloid plaque in obstructive sleep apnea patients in the same locations and spread the same way as in Alzheimer’s patients. While age is not a guarantee of Alzheimer’s disease or sleep apnea, age is a common risk factor for both diseases. Further recent studies published in the journal Frontiers in Aging Neuroscience found that the intermittent deprivation of oxygen during a sleep apnea episode may lead to the build-up of amyloid plaque in the brain, while the characteristic fragmented sleep associated with the disease may slow down the removal of toxins from the brain. Some risk factors for dementia include hypertension, cardiovascular disease, and diabetes. These chronic illnesses are also co-morbidities of OSA, showing yet another link between Alzheimer’s disease and sleep apnea.
Continuous positive airway pressure, or CPAP, is the gold standard in sleep apnea treatment. A recent study at Michigan Medicine’s Sleep Disorders Centers reviewed over 50,000 OSA patients, age 65 years and older. They found that those who used CPAP were less likely to receive a new dementia diagnosis over the next three years versus those who did not use CPAP.
Sleep's role in our overall health is at the center of the connection between OSA and Alzheimer’s disease. Researchers are hopeful that the diagnosis and treatment of OSA could lead to advances in the cognitive health of older adults.