Sleep Apnea May Lead to Early Cognitive Decline
A disorder in which breathing repeatedly stops during sleep, obstructive sleep apnea worsened memory and thinking in middle-aged men, a new study found.
Even in people who are otherwise healthy and not obese, obstructive sleep apnea (OSA) may contribute to early cognitive decline, according to new research.
The Sleep Foundation estimates that 10 to 30 percent of adults have OSA, which produces repeated breathing disruptions during sleep. These pauses in breathing have been linked to a range of serious health issues, including cardiovascular disease, diabetes, and even glaucoma. The disorder can also heighten the risk of early death.
Scientists have previously found that this intermittent cutting off of oxygen to the brain may affect its structure and function. Some research, however, attributes mental deficits in individuals with OSA to other co-occurring health problems (called comorbidities) associated with the apnea, such as hypertension, obesity, and small vessel disease in the brain.
“While we cannot claim causation, our findings suggest that obstructive sleep apnea itself may be sufficient to start damage in the brain, even in otherwise healthy patients,” says the lead study author, Ivana Rosenzweig, MD, a neuropsychiatrist who heads the Sleep and Brain Plasticity Centre at King’s College London.
Sleep Apnea Alone May Be Enough to Cause Cognitive Issues
Published April 6 in the journal Frontiers in Sleep, the study found that men with OSA experienced poorer short-term memory and executive functioning (the mental processes that enable us to plan, focus attention, remember, and juggle multiple tasks) than men without OSA. They also exhibited deficits in vigilance, sustained attention, and movement and impulse control.
Results were based on a group of 27 men between ages 35 and 70 with a new diagnosis of mild to severe OSA but without any comorbidities. Their outcomes were compared with seven matched controls — men without OSA or comorbidities.
The men were not currently smokers or alcohol abusers, and were not obese — their body mass index (BMI) was below 30. Cognitive ability was assessed through a series of neuropsychological tests.
Dr. Rosenzweig notes that one of the surprising outcomes was that participants with OSA also displayed deficits in social and emotional cognition.
“In our clinics, this has been often mentioned by patients’ partners. For example, the partners may sometimes report that a patient [with OSA] is ‘less emotionally present,’ or more irritable, or less altruistic. However, in studies so far, OSA has not been thought to be associated with this deficit,” says Rosenzweig.
Sleep apnea has also been linked with depression and anxiety.
The authors speculate that the cognitive deficits are due to intermittent low oxygen and high carbon dioxide in the blood, changes in blood flow to the brain, sleep fragmentation, and brain inflammation in people with OSA.
Rosenzweig further explains that during sleep, people with OSA may have a partial or full collapse of the upper airway in the neck because the airway is floppier during sleep, which then leads to drops in blood oxygen and other blood gas abnormalities, as well as disturbed sleep and changes in the brain’s passage of blood through the blood vessels.
Uninterrupted Sleep Is Essential for Brain Health
Colleen Lance, MD, a staff physician in the Sleep Disorders Center in the Neurological Institute at Cleveland Clinic, adds that the body and mind need both enough sleep and uninterrupted sleep for recovery.
“If your sleep time is cut short, or interrupted for whatever reason, there will be an impact on brain recovery resulting in cognitive decline,” says Dr. Lance, who was not involved in the new study. “For example, animal research in Alzheimer’s disease has shown that lack of sleep or interrupted sleep results in buildup of the proteins — let’s call it ‘trash’ — associated with Alzheimer’s disease. Sleep allows your brain to ‘take out the trash,’ if you will. OSA can cause a great deal of disruption, and in effect not allow your brain to catch up on its rest.”
According to Lance, the study is limited by its small number of participants, making conclusions difficult. The researchers say that a larger investigation is needed to confirm these preliminary results.
How Is Sleep Apnea Treated?
The American Academy of Sleep Medicine urges people with apnea to get treatment, but points out that 80 to 90 percent of adults with the condition don’t even know they have it because the stops in breathing occur while they're asleep.
A partner or someone who can observe you sleeping may help detect the condition. The Mayo Clinic lists other symptoms, including excessive daytime sleepiness, irritability, and awakening with a dry mouth.
The most common treatment for obstructive sleep apnea is a CPAP machine, which provides constant air pressure in your throat to keep the airway open when you breathe in. Lifestyle changes to lose weight can also help.
“This disorder is relatively easily treatable, and yet it can lead to such serious and debilitating diseases, which once set, may not be so easily treatable,” says Rosenzweig.