Obstructive sleep apnea (OSA) is a common problem, affecting over 935 million adults all over the world. The condition involvesTrusted Source upper airway collapse that then leads to someone waking up or experiencing drops in oxygen levels. But the possible effects of the condition may extend far beyond interruption of a good night’s sleep.
A recent studyTrusted Source published in JAMA Network OpenTrusted Source that involved an eight-year follow-up with over 1,400 participants found that there is an increased risk for cerebral microbleeds among adults who have moderate to severe OSA.
Cerebral microbleeds may increase the chances of experiencing symptomatic strokes and dementia. The authors suggest that addressing OSA may be a way to help with stroke and dementia prevention among older individuals.
Another potential risk posed by obstructive sleep apnea
For this study, researchers examined the relationship between OSA and cerebral microbleeds in older and middle-aged adults. Cerebral microbleeds involve a chronic buildup of certain blood products in the brain. As noted in the study, cerebral microbleeds are linked to a higher risk for symptomatic stroke and dementia and are more common in older adults.
Researchers selected study participants from a subcohort of the Korean Genome and Epidemiology Study. These individuals had undergone polysomnography, which helps to diagnose sleep disorders, as well as MRI exams.
Researchers selected participants who had undergone polysomnography and MRIs at three separate time points. They excluded individuals with a history of cerebrovascular disease or cardiovascular disease, missing covariates, or baseline microbleeds. The final analysis included 1,441 Korean adult participants.
Researchers were able to look at baseline brain data as well as brain data at the four and eight-year follow-ups.
Researchers took into consideration multiple covariates, including regular exercise, smoking status, blood pressure, and body mass index. Researchers did sensitivity analyses excluding participants who used CPAP therapy throughout the follow-up time frame, including a sensitivity analysis to account for the APOE-ε4Trusted Source geneTrusted Source, which is a genetic variant that increases risk for Alzheimer’s disease.
Researchers divided participants into three categories of OSA: none, mild, and moderate to severe. The average age of participants at baseline was just under fifty-eight years old. At baseline, 436 participants had mild OSA, and 193 had moderate to severe OSA. There was a higher proportion of men, current drinkers, and current smokers in the moderate to severe group, and body mass index was highest in this group as well.
The incidence of cerebral microbleeds was highest in the moderate to severe OSA group. For example, at the eight-year mark, 7.25% of participants in this group had cerebral microbleeds, while only 3.33% of participants in the group without OSA had cerebral microbleeds.
In the first few models, moderate to severe OSA was associated with an increased risk for cerebral microbleeds at the four and eight-year follow-up marks. However, in the final model, which adjusted for the most factors, the risk for cerebral microbleeds was only increased at the eight-year mark. For this, the risk was about double that of the group that did not have OSA.
Mild OSA was not associated with an increased risk for cerebral microbleeds.
2 times increased microbleed risk
In the sensitivity analyses, researchers found similar results. When considering the APOE-ε4 genotype, they used a subsample that excluded participants who didn’t have data on APOE-4.
The results were similar to the main analysis, with the relative risk actually appearing even higher. However, researchers believe this was due to the smaller sample size and the higher loss of participants with microbleeds in the group without OSA compared to those in the OSA group.
Overall, study author Chol Shin, MD, PhD, Institute of Human Genomic Study, College of Medicine, Korea University, highlighted the following to Medical News Today about the study’s findings:
“From a Korean population, sleep studies and brain MRIs over eight years revealed that adults with moderate to severe obstructive sleep apnea (OSA) were more than twice as likely to develop microbleeds in the brain than those without sleep apnea.”
Timothy J. Barreiro, DO, MPH, professor of internal medicine, section chair, pulmonary, critical care, and sleep medicine, director of the pulmonary health & research center, who was not involved in the study, added the following:
“The finding is particularly strong because the association (Relative Risk, 2.14) persisted even after rigorous adjustment for key vascular and demographic confounders, including hypertension, diabetes, body mass index, and APOE−ϵ4 carrier status. This independence suggests that the mechanisms inherent to severe OSA, such as nocturnal hypoxia, oxidative stress, and inflammatory responses, may play a direct role in damaging the endothelium of the vasculature.”
Where the study may fall short
While insightful, this study also has limitations.
First, this research focused on the Korean population, which limits generalizability to other groups. Work from other ethnicities and countries can add more data. Work in younger participants may also be warranted, since this study focused on middle-aged and older adults. Less than 200 participants had moderate to severe OSA at baseline, so more data on this group may be warranted in the future. Only a small number of participants carried the APOE-ε4 allele, and even fewer had the same allele type from both parents or were homozygousTrusted Source for this allele, further limiting the research.
There were a fairly small number of microbleeds that occurred, and those that did occur were single microbleeds. Therefore, researchers were limited in the analysis they could conduct. Because researchers identified cerebral microbleeds using a less sensitive method, they recognize that they may have underestimated them.
Additionally, there was a difference between the scanners used for the baseline brain imaging and at the four-year follow-up and what was used for the eight-year follow-up, which could have impacted the results. Researchers chose to exclude participants from analysis, such as those with missing data, so they acknowledge the possible risk of selection bias.
Some data on covariates were based on participant reporting, such as data on exercise, which could be incorrect. Additionally, while some participants reported CPAP use, research did not have data on how often they were using it.
Researchers note that “a potential healthy cohort effect due to the long-term follow-up over two decades may limit the overall generalizability of our study findings.”
Future research can explore the underlying mechanisms or why obstructive sleep apnea has this impact on risk for cerebral microbleeds, such as how inflammation and oxidative stress may be involved.
What this means for people with sleep apnea
The research does imply that addressing OSA is important because of the risks associated with it. There’s the possibility of preventing far worse outcomes.
“Preventive measures for OSA and early diagnosis and treatment are necessary, not just to improve one’s sleep quality but also to prevent chances of developing brain microbleeds — a precursor of future stroke and dementia,” explained Shin.
While more research on the benefits of obstructive sleep apnea treatment is needed, Stephen Carstensen, doctor of dental surgery and sleep expert, who was not involved in the study, also noted the following to Medical News Today:
“This study correlates higher levels of diagnosed sleep apnea with a bit more than double the chances of having a brain microbleed. This study gives solid medical-science reasons why getting diagnosed and treated early in life can help preserve brain health over the long term. This study was not about any protective effects of therapy, so we cannot use it to assure people that managing their sleep apnea with a dental device or CPAP lowers their risk of stroke, but other studies have shown that result.”
Medical myths: The mystery of sleep
Despite spending around one-third of our lives in the land of nod, sleep still holds many mysteries. Scientists are chipping away at the details, but the wonder of slumber is much more complex than it appears. In this Special Feature, we dispel some common myths.
Many animals need sleep of some kind, and if evolution has retained a behavior across many species, it must be important.
After all, lying unconscious for hours does not seem like the safest activity for an animal in the wild. So whatever goes on during sleep is vital.
“Those little slices of death,” as Edgar Allen Poe referred to sleep, help maintain good physical and mental health. The long-term effects of sleep loss are associatedTrusted Source with a range of health conditions, including diabetes, depression, stroke, and more.
However, because sleep has a perpetual association with the ethereal: dreams, altered states, and emotions, it is no surprise that it is tied to a legion of myths.
In this Special Feature, we address some of the most common myths related to the ubiquitous snooze.
1. Your brain shuts down during sleep
Thankfully, our brains do not quit their day job during sleep. Important functions, such as breathing, mean our brains can never fully shut down. In fact, during rapid eye movement (REM) sleep, when most dreams occur, brain wave activity is likeTrusted Source that of wakefulness.
Interestingly, despite the high level of activity, it is hardest to wake a sleeper during REM sleep. This is why this stage of sleep is sometimes called paradoxical sleep.
While we sleep, our white and gray matter has much to do. Once we have dropped off, our brain cycles through three stages of non-REM sleep, followed by one phase of REM sleep. In each of the four stages, the brain demonstrates specific brain wave patterns and neuronal activity.
This cycle of four stages repeats five or six times during a full night’s sleep.
While some regions of the brain fall quiet during non-REM sleep, other areas leap into action. For instance, the amygdala, most famous for its role in emotion, is activeTrusted Source during slumber.
The thalamus is an interesting case. This part of the brain is a relay station for our senses. What we see, hear, and feel arrives first at the thalamus. From there, sensory signals are ferried to the cerebral cortex, which makes sense of the inputs.
During non-REM sleep, the thalamus is relatively quiet. However, during REM sleep, the thalamus becomes active, and sends the cerebral cortex the sights and sounds of our dreams.
2. If you remember your dream, you slept well
Most people dream every night, yet we often don’t remember them. Dreams mostly occur during REM sleep, but they are almost immediately forgotten.
It is only when someone wakes during or just after REM sleep that the memory of a dream has not yet faded.
Some evidenceTrusted Source suggests certain neurons that are active during REM sleep might actively suppress dream memories.
These neurons produce melanin-concentrating hormone (MCH), which helps regulate sleep. MCH also inhibits the hippocampus, a key brain region for memory storage. One of the authors of the study linked above, Thomas Kilduff, Ph.D., explains:
“Since dreams are thought to occur primarily during REM sleep, the sleep stage when the MCH cells turn on, activation of these cells may prevent the content of a dream from being stored in the hippocampus — consequently, the dream is quickly forgotten.”
One study approaches this question from a different angle. The researchers recruited individuals who tend to remember their dreams most nights. They found that these people became wakeful during the night more often than people who more rarely remembered their dreams.
This suggests that people who often recall dreams might sleep less well.
In short, remembering a dream is not an indication of good sleep. It is just that you woke up at the right time to recall it.
3. Never wake up a sleepwalker
The common claim is that if you wake a sleepwalker, they might have a heart attack or even die. This is not true.
However, if someone wakes a sleepwalker, they can spark confusion and sometimes fear. Some sleepwalkers may act aggressively, so people need to be cautious if they wake them.
Sometimes, sleepwalkers can injure themselves as they navigate the house with their eyes closed. For this reason, the best course of action is to try and coax them back to the safety of their bed.
The United Kingdom’s National Health Service (NHS) website suggests that “the best thing to do if you see someone sleepwalking is to make sure they’re safe.”
The NHS website also explains once the sleepwalker has gone back to sleep and the episode is over, it is a good idea to gently wake them before allowing them to drop back to sleep. This might “prevent another episode occurring in the same deep-sleep cycle.”
They also add a note of caution: “Do not shout or startle the person and do not physically restrain them unless they’re in danger, as they may lash out.”
4. Alcohol guarantees a good night’s sleep
Alcohol reduces the amount of time it takes to get to sleep. Someone who has drunk alcohol might also be more difficult to rouse. Because of this, people often assume that it has a beneficial impact on sleep overall. This is not the case. The quality of sleep under the influence of alcohol is poorer in comparison to sleep without alcohol.
To awake feeling refreshed, our brain must cycle through the highly orchestrated series of phases and cycles mentioned earlier. Alcohol knocks this series of repetitions out of whack.
For instance, as the authors of a reviewTrusted Source on the topic explain, after drinking alcohol, “REM sleep reduction in the first part of sleep is significant. Total night REM sleep percentage is decreased in the majority of studies at moderate and high doses.”
According to another paperTrusted Source, which looks at the relationship between drugs and sleep more broadly, “self-reported sleep problems are highly prevalent among alcohol users with rates of clinical insomnia between approximately 35% and 70%.”
To summarize, while alcohol does get you to sleep quicker, the sleep you have will be less refreshing.
5. Cheese and other foods
This is an old myth that most people in the Western world will have heard. Although well known, one only has to eat cheese before bedtime to find that it is certainly not true for everyone.
However, eating a large meal just before bed, whether it includes cheese or not, can cause indigestion or heartburn, which could interfere with sleep.
If your sleep is disturbed by an active gut, and you become more wakeful more often, you will be more likely to remember any dreams you had. As mentioned earlier, people forget dreams almost as quickly as they form — unless you wake up during a dream, you are unlikely to remember it.
And, if your gut is uncomfortable, it might increase the chances of having an unpleasant dream.
The type of meal enjoyed before dinner could also make a difference. Dr. William Kormos, Editor in Chief of Harvard Men’s Health Watch, explains:
“[E]ating a large meal, especially a high-carbohydrate meal, could trigger night sweats because the body generates heat as it metabolizes the food.”
Again, this is likely to disrupt sleep, increase wakefulness, and therefore increase the likelihood of remembering dreams.
Why and how the cheese/nightmare myth began is unclear, but the fact that cheese boards tend to appear at the end of a large meal might offer some insight. Although some believe the origins of the cheese myth might lie in ancient legends.
A related myth is that certain foods, including milk, cheese, and turkey might help induce sleep. This is because they contain an amino acid called tryptophan.
Tryptophan is necessary for the body to make serotonin, which is necessary for the manufacture of melatonin, a hormone that plays a role in sleep.
Therefore, the theory goes that foods containing tryptophan might aid sleep. The most common of these myths is that Thanksgiving turkey, with its dose of tryptophan, makes someone sleepy after lunch.
However, studies investigating tryptophan intake have not found an overwhelming effect on sleep. Additionally, the levels of this acid in a portion of cheese or turkey are not high enough to make a difference.
The takehome
Sleep still holds many mysteries. Only through science and research can we eventually unlock more answers. However, as this article outlines, we have data to dispel many of the most entrenched myths.
For now, the best advice is to avoid late-night meals, reduce alcohol intake, and be gentle with sleepwalkers.
If you are struggling to get the sleep you need, here is a link to a Medical News Today article with useful tips for better sleeping.