Sleep apnea and pregnancy complications

Pregnancy is a time of rapid change in women's bodies. Sleep apnea can be more common due to weight gain and fluid retention (Restless legs syndrome is also more common - but that is for a separate post). This article discusses research presented at the American Thoracic Society's 2017 International conference. I did not attend this meeting. Researchers studied > 1.5 million pregnant women with a history of sleep apnea. The results showed that in women with obstructive sleep apnea there was a greater risk of serious pregnancy complications, longer hospital stays, and admission to the intensive care unit than mothers without the condition. However, treatment of sleep apnea was not determined, so it's not known if that would reduce the risk.

Obstructive sleep apnea, CPAP therapy, and diabetes

This study involved a large population of veterans diagnosed with obstructive sleep apnea (OSA). The study authors examined CPAP therapy usage and its effect on diabetes. The results showed that metabolic markers of diabetes were reduced in those patients that used the CPAP the most per night. Specifically, usage of at least 6 hours per night. The reduction in diabetes markers was not present in those with less nightly CPAP usage. Also, the risk of developing diabetes was reduced by those that used CPAP at least 6 hours per night. Finally, both of these findings were not influenced by the slight increase in weight observed during the follow up period measured.

Obstructive sleep apnea without obesity

Obstructive sleep apnea (OSA) is more common in obese individuals. Less is known about OSA in non-obese persons. This study looked at characteristics of OSA in non-obese people and compared them to OSA in obese people. In the introduction, the authors mention that non-obese individuals make up at least 20% of the adult OSA population. The authors also discussed that one reason non-obese people may have OSA is due to a low respiratory arousal threshold. This means that non-obese people may wake up more easily when their breathing tube collapses. In the study, the authors used information from sleep studies to estimate respiratory arousal threshold. The results showed that 25% of their patients were non-obese. And a higher proportion of non-obese patients had a low respiratory arousal threshold. Also CPAP usage was less in non-obese patients than obese patients. The authors concluded that non-obese patients may respond less to conventional OSA therapies (like CPAP) and that research is needed to discover alternative ways of treating OSA in non-obese patients.

High blood pressure medications and obstructive sleep apnea severity

Obstructive sleep apnea (OSA) is associated with high blood pressure (HTN). Studies have shown that OSA is independently associated with resistant HTN and it is believed that untreated OSA may worsen HTN. However, studies involving treatment of OSA with continuous positive airway pressure (CPAP) have demonstrated only modest improvement in daytime blood pressure in randomized control trials. some research first speculate that the relationship between OSA and HTN may be bidirectional.

With OSA, the muscles that make up the throat lose their home causing collapse of that area and reduction in airflow to the lungs. Research her as hypothesized that intensive blood pressure control may influence always say I stabilizing the upper airway. There is also evidence for the role of volume status affecting the severity of OSA. What this means is that some people have worse OSA when they have too much blood volume from conditions like heart failure or kidney failure.

This study theorized that it is at least plausible that intensive treatment of HTN may bring about improvement in the severity of OSA, either by volume control, stabilization of upper airway muscles, or perhaps because of some direct effect of blood pressure medications. The researchers conducted a systematic review and meta-analysis on this topic.

Although there were limited number of studies and the studies were not of high quality, though results revealed that there was a decrease in OSA severity after treatment with blood pressure medications. Of note, the decrease reached statistical significance but the researchers doubted if it would be clinically significant.

I wanted to blog about this study in part because because throughout my career as a sleep physician I have thought of the OSA-HTN relationship as more one way, with OSA contributing to HTN, rather than the opposite as suggested by the authors of this study. Certainly more studies will be required before any definitive conclusions can be made.

Snoring and obstructive sleep apnea

Snoring is a common problem among men and women and is one of the cardinal symptoms of obstructive sleep apnea (OSA). With the explosion of smartphones and the emphasis on in-home monitoring, sleep researchers have attempted to use measurement of snoring to determine risk of obstructive sleep apnea. It has been difficult to do this because not all people who snore have obstructive sleep apnea. In addition, sleep researchers don't agree on an objective definition of snoring or an established threshold level of loudness. The quality of snoring is determined by multiple factors including the stage of sleep, body position, use of alcohol or other sedating medications, and upper respiratory tract illnesses such as a cold. There is significant variation of snoring from night to night for no apparent reason as well. Finally, snoring can be chronic throughout the night or periodic meaning that there are periods of silence between snoring episodes. The periodic snoring may be more suggestive of obstructive sleep apnea.

This study evaluated the diagnostic value of periodic snoring sounds measured during home sleep apnea testing. Subjects that were at risk for obstructive sleep apnea were sent home with a home sleep study monitoring kit and worn while they slept. The home sleep study kit has a built-in microphone that is located on the chest to detect the snoring sounds. the results showed a strong positive correlation between the percentage of periodic snoring and obstructive sleep apnea severity (AHI). The correlation was strongest for younger subjects, females, and obese subjects. The researchers discussed that some women do not get evaluated for obstructive sleep apnea because they do not know that they snore or are embarrassed to report snoring. In my clinic, I find this to be the case as well. Therefore measuring snoring at home while the patient is asleep many help sleep physicians to recommend formal diagnostic sleep studies to accurately assess female patients without a strong history of snoring.

Sleep apnea and Meniere's Disease

Meniere's Disease involves the ear, and produces symptoms of hearing loss, tinnitus (ringing in the ears), and vertigo (a form of dizziness). Nausea and vomiting often accompany the vertigo. Meniere's Disease is usually treated with medications, but that does not always help. Some research has pointed to an association of poor sleep quality and Meniere's Disease. Obstructive sleep apnea (OSA) can result in poor sleep quality and could worsen Menierie's.

This small study looked at the effect of 6 months of CPAP therapy on Meniere's Disease. All 20 patients had failed medication management of Meniere's Disease. All had OSA diagnosed with a sleep study, and all used CPAP therapy only. They did not restart their Meniere's medications during this study. Results showed that CPAP therapy by itself reduced the impact of the vertigo and the low-frequency hearing loss associated with Meniere's disease.

The reason that treating OSA may help Meniere's is unknown. The study authors speculate that elimination of low oxygen levels when asleep may be the factor that improves the Meniere's. I also wonder if elimination of the snoring helps.

CPAP use, obstructive sleep apnea, and cardiac function

Studies have shown that obstructive sleep apnea (OSA) can negatively impact cardiac function, especially if the OSA is severe. And studies have shown that treating severe OSA with CPAP can improve cardiac function. However, studies have not shown clearly that treating milder cases of OSA provides significant cardiac benefit.

This study looked at patients with mild-to-moderate OSA with mild cardiac dysfunction. Patients were minimally symptomatic with regards to OSA as well. Patients were either given CPAP for 6 months or given no CPAP. Compliance with CPAP was determined based on the CPAP download. The results did not show any convincing change in cardiac function or structure after 6 months of CPAP usage. There was no dose response effect with CPAP usage either, meaning that there still was no change in cardiac function in those that used CPAP the longest per night.

The researchers concluded that CPAP use in patients with mild OSA and mild cardiac dysfunction may not be as helpful as traditional cardiac dysfunction treatments like blood pressure medications.

Obstructive sleep apnea may disrupt the blood brain barrier

The blood brain barrier is like a wall that has holes in it. It allows good substances to cross from the blood vessels into the brain. At the same time, it keeps out harmful substances like bacteria and some toxins. According to this article, researchers think that some illnesses may result from the breakdown of the blood brain barrier.

The article discusses a research study showing that untreated obstructive sleep apnea (OSA) can breakdown the blood brain barrier. The researchers think that the low oxygen levels associated with OSA are responsible for the breakdown. But the breakdown may be what causes some of the symptoms of OSA, such as memory or mood problems. The researchers also think that repairing the blood brain barrier may improve these symptoms in patients with OSA. I also wonder if treating the OSA repairs the blood brain barrier - more studies will be needed to figure that out.

Sleep-related breathing disorders, functional disorders, and anxiety disorders

Here is a fascinating article (at least to me) about a possible link between sleep-related breathing disorders like obstructive sleep apnea and other disorders. The other disorders are classified as "functional", meaning no etiology is agreed upon, such as fibromyalgia, chronic fatigue syndrome, and migraines. The other disorders include anxiety disorders like panic attacks and post-traumatic stress disorder (PTSD).

The researcher that is discussed in article is Dr. Gold at Stony Brook University and has published research studies on this topic. His theories about how mild OSA disorders can worsen functional and anxiety disorders is not without controversy. However, if further research confirms his theories, treatment for OSA may also help these difficult-to-treat disorders.

Jaw surgery for obstructive sleep apnea

For most people with obstructive sleep apnea (OSA) that is at least moderate severity, CPAP is the most effective treatment option. However, for the right patient, jaw surgery can be very effective as well. The type of jaw surgery that is done is where the oral surgeon breaks the lower (and usually the upper) jaw to reposition it away from the face. This opens up the breathing tube, resulting in less obstruction. There is data showing short term effectiveness of this procedure, but little long term efficacy data. This study does just that.

The study participants were adults who had moderate or severe OSA. Sleep studies were done pre- and post-op jaw surgery, as well as at least 2 years after the surgery. Results showed that the average OSA severity reduced by almost 77% over the long term. And 47% of patients did not meet criteria for OSA post-op. Finally, 83% of patients had mild OSA but no excess sleepiness post-op. Blood pressure was decreased and quality of life increased after the jaw surgery. These improvements in OSA severity and blood pressure occurred despite an increase in weight during the followup period.

Micro-CPAP

I've been asked by multiple patients in the past few weeks about this tiny CPAP, the Airing. I don't know anything about it other than what is in this article. It looks interesting, but I have many questions about it. If it gets FDA approval, we will learn much more.

CPAP therapy and cognitive performance in elderly patients with severe obstructive sleep apnea

Obstructive sleep apnea (OSA) is more common with age, regardless of weight. OSA in elderly patients can contribute to daytime sleepiness and impair cognitive performance. OSA has even been associated with development of early dementia, called mild cognitive impairment. There is not a lot of data showing the effects of CPAP use on cognitive functioning in elderly patients. But that is just what this study sought to do.

The study population was a subset of a larger study, and participants were at least 65 years old. Participants received extensive neuropsychological testing at the start and end of the study period (6-10 years between the two time points). Participants had a sleep study at the beginning of the study and only those with severe OSA were included. The researchers then divided the participants into those that used CPAP therapy and those that did not. This was a smaller study, with only 126 subjects included, 33 of which used CPAP. Also, note that CPAP use was determined by the patient's self-report. In other words, CPAP use was not determined objectively by checking what the CPAP machine had recorded. So it's possible that CPAP use may have been over-estimated. The researchers also did not separate out CPAP use into the number of hours per night - participants either did or did not report CPAP use. Interestingly, all of the CPAP users reported using CPAP for the minimal 4 hours per night. Finally, participants who used CPAP tended to have more severe OSA, were more overweight, and had more daytime sleepiness. There was no difference in age, gender, or level of education in those that used CPAP versus those that did not.

The results showed that subjects with OSA had a more severe deterioration of cognitive function and memory over time. Also, CPAP therapy helped preserve some cognitive functions like memory, attention, and decision making ability. The authors concluded that long term CPAP use is associated with a protective effect on cognitive performance in elderly patients with severe OSA. They suggest that physicians who treat elderly patients consider screening for and treating OSA to help maintain cognitive performance.

CPAP and blood sugar levels in Prediabetes

Prediabetes is a condition in which blood sugar levels are elevated above normal, but not high enough to meet criteria for diabetes. Here is a study that measured blood sugar levels (and other parameters) during two weeks of CPAP use versus an oral placebo in patients diagnosed with obstructive sleep apnea. I only have access to the abstract and an article about the study. In this study, researchers ensured that those randomized to CPAP used it for 8 hours a night for two weeks straight. The results showed that the CPAP users had lower blood sugar levels as the main outcome. A secondary outcome measure showed lower blood pressure levels in the CPAP users when compared to the controls.

Obstructive sleep apnea and tooth wear

In my practice, I see lots of patients with excessive tooth wear, or irreversible loss of the tops of the teeth. It gets more common with age. It's not always due to teeth grinding - it can occur from eating certain foods, especially those high in acidity. This study looked at the association between tooth wear and obstructive sleep apnea (OSA). This was a study done in a private dental clinic in Spain, and patients diagnosed with tooth wear each had an overnight home sleep study to assess for OSA. The results showed that the prevalence of OSA was three times higher in patients with tooth wear. And there was a positive correlation between OSA severity and tooth wear, meaning the more severe the OSA, the more severe the tooth wear. The relationship was not diminished after controlling for body mass index, age, and gender.

The study authors speculated that there could be a common mechanism behind the OSA and tooth wear, such as arousal from sleep contributing to tooth clenching or grinding. The study authors also pointed out that the association between OSA and tooth wear could be coincidental, as both conditions become more prevalent with advancing age.

Finally, the study authors recommended that dentists consider referring patients with tooth wear to their primary care provider or sleep doctor for evaluation of possible OSA.

Sleep apnea and high blood pressure

Another post about obstructive sleep apnea (OSA) and high blood pressure (HTN). This study is a meta-analysis of observational studies and randomized controlled clinical trials. The study authors studied patients with resistant HTN, meaning blood pressure that was not responding to multiple medications. The study participants also had OSA.

I don't have access to full article, only the link above and the abstract. The results suggest that those patients with the highest blood pressures had the greatest reduction in blood pressure after using CPAP therapy. The study authors concluded that untreated OSA may be why some patients' blood pressure just won't come down with multiple medications.

The results from this study are not new, but do provide more evidence of the importance of screening patients with resistant HTN for underlying OSA. In my community, primary care doctors have been doing this for years already. However, this may not be the case in other medical communities around the country.

Blood pressure and sleep apnea

Several research studies have linked high blood pressure (HTN) to obstructive sleep apnea (OSA). The etiology is not clear, however. With OSA, there is sleep disturbance from brief awakenings, thought secondary to adrenaline release that is triggered when breathing resumes. Also, oxygen level reductions, called desaturations, could lead to elevated blood pressures. Respiratory events that are detected during a sleep study have specific scoring criteria - the event has to last at least 10 seconds and result in either a brief arousal from sleep and / or an oxygen desaturation.

This study sought to determine which types of respiratory events were most likely to result in HTN. The researchers followed 2040 participants and used sophisticated statistical models to study the sleep study results and blood pressure measurements. Results showed that those respiratory events with at least a 4% oxygen desaturation were most consistently associated with HTN. Interestingly, the other sleep study measurement that correlated with HTN was periodic limb movements that resulted in brief arousals from sleep.

CPAP use after weight-loss surgery

Obstructive sleep apnea (OSA) and obesity are related. Weight loss can improve OSA, sometimes enough to eliminate it altogether. However, if OSA is severe, weight loss alone is often not enough to cure OSA.

Most patients who undergo weight loss surgery have OSA, and most use CPAP prior to weight loss surgery. Unfortunately, most patients discontinue their CPAP use after weight loss surgery. This study assessed long-term CPAP use in 21 patients who had undergone gastric banding. Results showed that body-mass index significantly increased by 6.8 in those patients who did not use their CPAP after weight loss surgery. And BMI dropped by 1.8 in those patients that were adherent to CPAP therapy after weight loss surgery.

Another important point is that OSA persisted in almost all of the patients who underwent the surgery, despite the substantial weight loss (average 121 pounds lost). And, after 7.2 years of follow up, the majority of patients had gained back some weight (22 pounds).

So the data in this study suggest that CPAP adherence for the long term may help with weight loss maintenance. Remember this is a small study though. Other confounding factors could contribute to reasons why some patients chose to keep using CPAP. For instance, some may have continued only because using CPAP made them sleep better or have more energy. And that increased energy could have helped them keep exercising, which may help maintain weight. Or those that kept using CPAP may have adhered better to diet restrictions.

In the end, follow up with the sleep medicine specialist is important after weight loss surgery. In that way, post-operative OSA severity can be assessed after the first year. Then, the patient and sleep medicine physician can discuss the pros and cons of continuing CPAP therapy if necessary.

Sleep apnea, motor vehicle accidents, and CPAP therapy

There are recent meta-analyses showing higher risk of motor vehicle accidents (MVA) in those with obstructive sleep apnea (OSA), and a lower risk of MVA with CPAP therapy. However, the conclusions from these studies is somewhat limited due to possibly faulty research designs. In other words, it's still uncertain how much risk OSA imparts and if CPAP really reduces that risk. However, this study, recently in the Sleep Journal, set out to determine just that, using a well designed protocol. It was a retrospective study of almost 1500 drivers in Sweden. The results showed that there was a 2.5 fold increase in risk of MVA in patients with OSA. The risk was highest in older drivers. Also, risk was highest in those with high subjective sleepiness, but the risk did not depend on OSA severity. And the incidence of MVA was reduced by 70% among patients that used their CPAP at least 4 hours per night. Interestingly, risk of MVA was increased by 54% among those that used CPAP less than 4 hours per night.

The authors concluded that because CPAP therapy can improve sleep quality and overnight oxygenation, it could improve alertness and driving performance - leading to less MVA's.

Treating obstructive sleep apnea with medication

Obstructive sleep apnea (OSA) is currently treated with mechanical devices - air pressure from CPAP, jaw movement with oral appliance therapy, or surgical therapy. No medications have been shown to be particularly helpful in treating OSA. This article discusses NIH funding given to a team of researchers at the University of Chicago.

The article describes the research already going on at the University that focuses on a small group of cells in the carotid artery called the carotid bodies. When levels of oxygen in the blood drop, these carotid bodies send signals to the brainstem to increase breathing, with the goal of increasing oxygen levels in the blood. The article describes that in sleep apnea, the carotid bodies may not react appropriately, and thus stop sending signals to the brain. The University of Chicago team has developed a compound that may help the carotid bodies to keep working properly during sleep apnea, and thus aid in their regulation of breathing - at least in rodents.

However, it's not clear what type of sleep apnea the researchers are working on. It sounds like central sleep apnea (CSA), which is a completely different, and less common form of sleep apnea, than OSA. In most cases of OSA, the drive to breathe is intact, but airflow is significantly reduced due to a blockage in the upper airway. In addition, not every patient with OSA has oxygen level reductions, even though airflow through the upper airway is reduced. But if a person with OSA has regular blood oxygen level reductions, perhaps a medication that helps the carotid bodies stimulate breathing may be effective, if that stimulation involves increasing the diameter of the upper airway.

Asthma and obstructive sleep apnea

This article is about a study showing an association between asthma and risk of obstructive sleep apnea (OSA). All participants were adults drawn from a random sample of Wisconsin state employees. Initially they were free of OSA based on overnight sleep studies done every 4 years. Results showed that the relative risk of developing OSA was 1.39 times higher in those with asthma. And this was after adjusting for sex, age, baseline and change in body mass index, and other factors. The study authors suggest that physicians who treat asthma should periodically screen those patients for OSA.