Do you snore through the night? Snoring is a sign that you may have obstructive sleep apnea (OSA). Sleep apnea affects 1 in 5 people, but this number rises dramatically for stroke patients. Up to 70% of stroke patients suffer from OSA. Though there isn’t any physical pain, sleep apnea can have a significant impact on someone’s daily life. It can make you extremely exhausted during the day and even contribute to memory problems.
What came first?
There’s somewhat of a chicken and egg problem when it comes to stroke and sleep apnea. Is OSA a risk factor for stroke? Or does a stroke put you at higher risk of developing OSA? Likely, there’s a little bit of both at play here, but researchers decided to investigate this association further.
Chinese researchers studied the influence of OSA on cognitive functions like memory and attention, with a particular focus on time-based and event-based prospective memory. Prospective memory is a type of memory that refers to the act of remembering future actions that were pre-emptively planned.
This is a prospective case-control study that took place in China between June 2013 and June 2015. Researchers recruited 44 stroke patients, as well as 24 controls (i.e., patients who didn’t have a stroke yet still had OSA) to participate in the study. All participants were asked to take cognitive tests and had their sleep monitored overnight. The researchers found that stroke patients who had OSA fared much worse in prospective memory tests than stroke patients without OSA, before and after “cleaning away” other medical conditions which might have influenced the results. The researchers concluded that having sleep apnea likely worsened the patient’s memory in a way that was unrelated to stroke after-effects.
OSA also seemed to correlate with the severity of memory problems. Though it would seem to make sense that getting a less restful sleep would negatively affect anyone’s memory, this study revealed something interesting. It discovered that stroke patients were much more sensitive to this effect. It’s likely that a stroke makes the brain much more vulnerable to memory problems caused by sleep apnea.
One possible explanation for why OSA affects memory problems is that it causes blood oxygen levels to decrease. Having less oxygen in your bloodstream means less oxygen to the brain, which is essential for proper brain functions including memory. Another explanation could be that disrupted sleep leads to memory issues, just because you are more fatigued and mentally exhausted from lack of restful sleep.
With that said, it is important to remember this is a small, single-center study. Therefore, conclusions must be carefully approached. Future studies with a more substantial number of patients are needed.
If you snore and have suffered a stroke, don’t lose faith just yet! There are ways to treat OSA and improve your sleep. Treatments that help you breathe better at night enhance your sleep and improve memory in stroke patients. Though breathing machines can be expensive, costing anywhere from a few hundred to a few thousand dollars, many insurance policies will cover the costs for you. Talk to your doctor about your treatment options. You can benefit from a good night’s rest and improve your memory!
The lead author was Yan Zhang, from the Department of Neurology at the Kunshan Affiliated Hospital of Jiangsu University, Kunshan, China.