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The Relationship Between Stroke and OSA
The Relationship Between Stroke and OSA Recording
The Relationship Between Stroke and OSA Recording
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But today I'll be talking to you about stroke and obstructive sleep apnea. I have no conflicts of interest regarding this presentation. So let's talk a little bit about background. So why as a sleep medicine physician or a sleep medicine provider should I care about stroke? Well, we know that stroke and sleep disordered breathing have a bi-directional relationship with sleep disordered breathing leading to hypoxemia, arrhythmia, inflammation, vascular disease, which then increases your risk of stroke, which thereby increases facial motor weakness, airway collapsibility, increased supine sleep position, altered respiratory control, and then that leads back to sleep disordered breathing. We know that stroke was the leading, fifth leading cause of death in the United States, but it was recently displaced by SARS-CoV-2 and it's highly prevalent in ischemic stroke patients. Sleep disordered breathing is also associated with worse stroke outcomes. Sleep disordered breathing is treatable and sleep medicine represents a critical value addition to stroke prevention and care. Much of preventive care is deferred to primary care and so the management of sleep apnea is deferred to us, sleep medicine specialists, sleep medicine dentists. And so the concept of added value is one of increasing relevance for our field as a whole. Sleep disordered breathing is a condition that is prevalent before stroke. Sleep disordered breathing independently increases your stroke risk and worsens other stroke risk factors, hypertension and atrial fibrillation. Now, when we compare stroke with sleep disordered breathing versus stroke without sleep disordered breathing, we know that stroke with sleep disordered breathing is more prone to early neurological worsening, longer hospital stays, and worse cognitive and functional recovery. And so in 2014, the American Heart Association, along with the American Stroke Association in their stroke guidelines, included for the first time, recommendation to screen for obstructive sleep apnea and consider treatment with CPAP in patients with ischemic stroke or TIA. And in the last decade, as we all know, home sleep apnea testing has really facilitated the diagnosis in patients with stroke. So, and then there have been, over the past couple of years, there've been many important manuscripts that have been published exploring the link between sleep disordered breathing and stroke. And I'm gonna try and go through as many of them as I can for you today. So let's talk about prevalence of sleep disordered breathing after stroke. So in 2019, in neurology, a meta-analysis was published with pretty much all of the data up to April, 2017. It had 86 studies with over 7,000 patients. Most of the strokes included were ischemic stroke, about 75%. And in terms of diagnostic studies, about half were full PSG and another 40% were the type three studies. The overall prevalence of sleep disordered breathing with an AHI of greater than five was about 70%. And then with an AHI of greater than 30 was about 30%. And this was consistent with a smaller 2010 meta-analysis which had only 30 studies at the time. But this may also actually be an underestimation because most of the analyzed studies were biased towards mildly affected strokes, excluding those with very severe comorbid conditions. And those comorbid conditions are risk factors for stroke compared to healthier individuals. And so in this meta-analysis, if we look at the forest plot here, the mean AHI remained high from acute to chronic phase after stroke. So in the acute phase at less than one month, you had a mean AHI of about 25. The subacute phase, it was about 40, but that was influenced by one smaller study. And then in the chronic phase, again, it was about 25. There was no clear tendency towards a decrease in apnea over time as reported in prior longitudinal studies. And if we look at the prevalence across sleep disordered breathing thresholds, it remains similar from acute to chronic phase after stroke in terms of how many patients have mild, how many patients have moderate, how many patients have severe sleep apnea in the acute, subacute, and chronic phase. So the overall, in terms of central sleep apnea, if we define central sleep apnea as more than 50% of total apnea scored as central, if we use a threshold of five events per hour, it was about 12% had central sleep apnea. There was no data available to calculate prevalence in the moderate and severe categories, but this confirms what we already knew, that there's a predominance of obstructive rather than central events in line with prior studies and prior meta-analyses. But again, there may be an underestimation of central sleep apnea because the patients with central sleep apnea were excluded for many of these trials. So let's talk about recurrence, recurrence risk of stroke outcomes, and the evolution of stroke. So this study by the University of Michigan, ischemic stroke patients in Corpus Christi, Texas, in an ongoing stroke surveillance study were offered home sleep apnea testing with a type three device as soon as possible after stroke onset and often during their hospitalization. They had about, they had over 800 patients and about 63% had an REI greater than 10. So most had mild to moderate sleep apnea. And they chose an REI threshold of 10 versus the more typical number of five for two reasons. The type three devices have a higher sensitivity and specificity at a threshold of 10. And if they chose five, then nearly all of their stroke patients would have met criteria for sleep apnea. So the median time from stroke symptom onset to sleep disorder breathing assessment was about 13 days. So it wasn't always immediate. And the median follow-up in this study was about, was over 1.5 years of follow-up time. So they found that sleep disorder breathing was correlated with male sex, Mexican-American ethnicity compared to other ethnicities, hypertension, diabetes, higher body mass index. And in adjusted and unadjusted analysis, the REI was associated with recurrent ischemic stroke. So for a 20 unit increase in REI was associated with a recurrent stroke hazard at a hazard ratio of about 1.6. But REI was not associated with post-stroke mortality. This same group, they did a study where they did the home sleep apnea testing, and then it did outcome interviews at 90 days after stroke. They had over almost close to a thousand patients from 2010 to 2015. Most of them were Mexican-American because it was in Corpus Christi, Texas. And so they were looking at four stroke outcome categories, neurological, functional, cognitive, and quality of life. And the neurological outcomes were assessed by the NIH Stroke Scale, which is described here. The functional outcomes were assessed by two instruments, the activities of daily living and the instrumental activities of daily living. Cognitive outcomes were assessed by a mini mental status examination, and quality of life was assessed using a stroke specific quality of life scale. So what they found was with sleep disordered breathing with your REI threshold greater than or equal to 10, when you adjust for confounders accounted for worse functional outcomes, an increase in the ADL instrumental activities of daily living, worse cognitive outcomes, a decrease on the mini mental status, but no changes in the NIH Stroke Scale or the sleep quality of life indicator. So, and these models were adjusted for all sorts of things. Mexican-Americans had a higher prevalence of sleep disordered breathing and worse outcome across all four outcomes. So being Mexican-American accounted for 10% of a difference in functional outcome, 10% difference in cognitive outcome, a 6% difference in quality of life and a 4% difference in your NIH Stroke Scale. So it was, these were significant findings. This study was from JCSM, Journal of Clinical Sleep Medicine 2018 was a prospective study of 177 patients in Finland with ischemic stroke. Some had TPA, some didn't have TPA and they were followed over six months. Sleep apnea here was defined as an REI greater than five and they assessed the progression of sleep apnea prevalence over six months in the overall group, the TPA group and the non-TPA group. And so at baseline, there was no real, there was a little bit of a difference in sleep apnea prevalence between the groups with more sleep apnea in the folks who got TPA, but at six months, there was no difference in sleep apnea, whether you got TPA or didn't get TPA. And if you look at changes in sleep apnea severity over six months, mild apnea progressed to moderate, to severe and almost 70%, but moderate improved to mild at about 20%. But the mean REI changes, there was a decrease in REI in the TPA, a little bit of an increase in the non-TPA group, but these results were not statistically significant. So it's hard to draw conclusions whether TPA had an influence in stroke evolution here. Screening for sleep apnea. And this is, a lot of studies have been published recently about screening and this is especially useful for folks we see on the front line. This study was a retrospective study published in the Journal of Clinical Sleep Medicine in 2019. It was a retrospective study of about 1,000 patients admitted to Mayo Jacksonville, Florida for acute ischemic stroke from 2008 to 2014. 19% had OSA, 60% were confirmed with either a PSG, some were just by clinical history. And then this other group was a probable diagnosis, which was based on an abnormal oximetry finding. Adherence to PAP was based on chart review and they were trying to see how adherent people were prior to admission for the acute ischemic stroke. Only 25% used the PAP more than four hours a night. 16 had rare or no use of CPAP and more than 50%, there was no adherence data available in the electronic medical record. And about 22% received treatment for sleep apnea during their hospital stay, possibly auto CPAP, but it wasn't really clear from the paper. And so the University of Michigan group again, led by Brown et al, was also wanted to assess how common sleep apnea screening was after stroke. So it was again, the Corpus Christi Stroke Surveillance Study. Patients were interviewed at baseline in reference to the pre-stroke period, again at 90 days in reference to the post-stroke period. And the questions include whether any clinical provider directly asked them about snoring or daytime sleepiness, or they had been offered a PSG. So it was close to a thousand participants. And in the pre-stroke period, only 9% were asked about snoring, only 9% were asked about daytime sleepiness, and only 17% were offered a sleep study. And out of these only 14% had it completed. In the post-stroke period, 5% were asked about snoring, 10% again were asked about daytime sleepiness, only 6% were offered a study. And out of these only 2% had a completed test. So really these are pretty dismal numbers. So screening for sleep apnea is important. And so this was a paper a little bit earlier, 2016, where they were comparing the different models of the Stop-Bang questionnaire, which I'm sure we're all familiar with. They're comparing Stop-Bang to other forms of it. So the Stop-Bag, which is the Stop-Bang without the neck circumference, and a Stop-Bag 2, which is a stop score plus sex and continuous variables for BMI and age. So that requires a calculation and estimates probability of having OSA defined as an age greater than or equal to 10. And so the neck circumference did not improve the performance of the Stop-Bang compared to the Stop-Bag. So, which is useful because neck circumference is not routinely acquired in outpatient clinics, even in stroke clinics. We don't measure neck circumference. The Stop-Bag 2, which is with the score and the continuous variables, which require calculation, had only a slightly higher sensitivity and specificity compared to the Stop-Bag. So the benefit is that the Stop-Bag doesn't require this automated calculation. It's easier to do. And there wasn't so many, so it wasn't much of a difference between Stop-Bag 2 and the Stop-Bag. So this was a study looking at Stop-Bang and nocturnal oxygen desaturation to predict OSA after stroke. So patients had completed the Stop-Bag with the Stop-Bang without the neck circumference and a PSG or home sleep apnea test within 12 months of their stroke or TIA. And if the lowest oxygen desat from the PSG or the HST was less than or equal to 88%, they were given an additional point to the Stop-Bag score, hence this Stop-Bag O score. And so if you look at the table, the sensitivity for Stop-Bag versus the Stop-Bag O, the sensitivity was 67% compared to 83%, specificity of 78% compared to 95%. So the Stop-Bag O score seemed to be a valid tool for identifying the risk of OSA post-stroke and TIA. And the simplicity of the tool and the ease of assessing nocturnal oxygen desaturation made it a feasible option for more widespread use. And so the idea that if you get, you can assess people's nocturnal oxygen desaturation, add it to the Stop-Bag score, and these pulse oxes are available everywhere nowadays, people can buy them on Amazon. And this, it can help provide really useful data, increasing sensitivity and specificity for stroke prediction, or for sleep apnea prediction, excuse me. Okay, so this is another study looking at oximetry for identifying moderate to severe apnea in acute stroke. This was published in JCSM in 2018. It was at Boston Medical Center. 270 inpatients with acute stroke underwent the home sleep apnea test while in hospital. So the AASM practice guidelines recommend PSG rather than HST with stroke, but that might not be practical due to insurance limitations, cost, availability. In this study, it was interesting because the neurology residents were instructed on how to connect and disconnect the type three devices, which is, again, you don't need text to do it. And then two measures were assessed, the oxygen desaturation index, which is described here, and the cumulative time at a saturation less than 90. And so if we look at these receiver operating characteristic curves, these curves are plots that illustrate the diagnostic ability of a binary classifier as the threshold is varied. So a value of one is a perfect test, and a value of 0.5 is an almost worthless test. So if we look at oxygen desaturation index to predict respiratory event index, you can see that ODI is much more useful than CT90 here in predicting mild, moderate, or severe apnea if you look at the area under the curve scores. And so oxygen desaturation index, more useful than time under 90% as a discriminator. ODI greater than 5% essentially, greater than five events per hour rules in sleep disorder breathing at a specificity of 90% and a positive predictive value, 96%. An ODI of greater than or equal to 15 rules in moderate to severe sleep disorder breathing at a specificity and a positive predictive value of over 95%. And the ODI of less than five rules out moderate to severe sleep apnea at a sensitivity and a negative predictive value at 100%. So it's really, it shows the power of oximetry here, oxygen desaturation index. Okay, so let's talk about CPAP here. And there's been quite a few studies recently about showing some interesting information about CPAP. This made big headlines in 2016, this New England Journal of Medicine article, CPAP for the prevention of cerebrovascular events and obstructive sleep apnea. This was the SAVE trial, the Sleep Apnea Cardiovascular Endpoint Trial. So they were treating patients with cardiovascular disease and moderate to severe OSA with CPAP. And it showed it did not prevent serious cardiovascular outcomes. So there were a couple of, this was a kind of a very unexpected finding, but there were potential explanations here. There was a non-significant less than one millimeter systolic blood pressure difference between the CPAP treated group and the usual care group. And there was a high level of background antihypertensive use. And there was a small potential effect size of CPAP on mean blood pressure and mean blood pressure then as a consequence on cardiovascular outcomes. So over 2000 patients were randomized, 1300 were in the CPAP group, and only 42% had good adherence described as relatively modest, greater than or equal to four hours per night of use. But those with the good adherence, when you compared them to the usual care group, there was a lower risk of stroke and a lower risk of stroke and TIA when you put them together. So it's possible that more highly adherent OSA populations were required to show that CPAP treatment can reduce stroke risk. So that's some of the takeaway from this SAVE trial in 2016. And so the same group that did the SAVE trial in 2016, in 2019, they wanted to analyze their data further. And so they had an analysis of mean blood pressure and visit to visit blood pressure variability. And blood pressure variability was defined as the standard deviation of blood pressure across visits for each participant. So at one month, at three months, six months and 12 months, the mean systolic BP and the mean diastolic BP were significantly lower in the CPAP group compared to the usual care group. But there was no change at 24 months. And there was no significant difference between the groups and systolic blood pressure variability or diastolic blood pressure variability over two years. And if you look at the Cox regression analysis for systolic BP, systolic blood pressure variability, as predictors of heart attack and stroke, when you adjust for all sorts of things in the fully adjusted model, across both treatment and usual care group, mean systolic blood pressure and systolic blood pressure variability were significant predictors of stroke. So there was some signal here. And so that was the SAVE group and their re-analysis of some data. This was a study published in Stroke in 2018. It was a post hoc analysis of a large prospective observational cohort from Europe. And they had four groups, a control group which they considered an AHI of less than 15, an untreated moderate OSA group with AHI of 15 to 30, no CPAP or poor adherence to CPAP, an untreated severe OSA group, and an OSA with CPAP group. So AHI greater than or equal to 15 with good CPAP adherence. And good CPAP adherence is as typically defined as greater than four hours per night. And so if you look at the Kaplan-Meier survival curves here, you could see that when you compare the AHI less than 15 to the OSA with CPAP, to the moderate OSA with no CPAP, to the AHI greater than 30 with no CPAP, there for all comparison groups versus the severe sleep apnea with no CPAP, the P value was less than 0.01. And so there was a significant difference. And so as opposed to, so for stroke, there was a difference. So the cumulative incidence for stroke was significantly higher in the untreated severe OSA group. But there was no such difference when they were looking at coronary heart disease, which is on the right side, the Kaplan-Meier curve on the right side. Okay, so I tried to put together some of the data, the most recent data for you in terms of recent randomized controlled trials of CPAP and stroke recovery with treatment of at least four weeks. And so this is, the first study is a study from 2006 with 15 patients, eight weeks, they were treated on a rehab unit in the United Kingdom, treated with auto CPAP. And out of the 15 patients who had an AHI greater than 30, seven out of the 15 used the device for more than four weeks, but the average use was only one hour a night. So obviously they didn't see any improvement in stroke or cognitive function, which is not so surprising. Then in 2011, there was another study with 16 patients, AHI greater than five, 30 days, treated in the hospital or at home. The average use was about five hours. And so there was an improvement in stroke severity measured by the NIH Stroke Scale with greater improvement the more they use CPAP. The Michigan group in 2013 did a similar study with 15 patients, AHI greater than five, almost half dropped out and the remaining half, the average use was about four hours a night. They didn't see any improvement, but this was such a small number of patients. This, the next study was a European study with more patients. They looked at them for over two years. There was no clear dropouts reported in this study over two years, which is extraordinarily unlikely. So it's hard to know, hard to judge this paper. And the average CPAP use was about five hours and they noticed improvement in ADLs and stroke severity over time. And this is the same cohort that we just looked at, looked at them over two years. And then they did telephone calls at five years that determined cardiovascular events and mortality. And so here are the two Kaplan-Meier survival curves. And so at five years, there was a statistically significant increase in cardiovascular survival, but not event-free survival compared, when you compare the control of the OSA without the CPAP group. So these are the Kaplan-Meier survival curves down here and you could see the curves. This is another study from 2011, 25 patients with an AHI greater than or equal to 15. 22 out of the 25 used the device over almost five hours per night. And there was improvement in stroke severity and improvement in motor components too and functional impairment. This was another study where the results, the average use of CPAP here was only about two hours per night and they didn't notice a lot of improvement in ADLs or stroke severity or improvement with CPAP. Okay. This is a study, this was a very interesting study. This was published in 2016, 20 patients who had an AHI greater than or equal to five. They were 18 months in a rehab unit. They were treated, they were diagnosed with in-lab PSG or HST. They were treated with APAP, but the control group had a sham APAP, a fake APAP. And so seven out of the 20 dropped out, but 13 out of the 20, the average CPAP use was four hours. There was no significant difference in adherence between real APAP and fake APAP and the intention to treat analysis of this functional independent measure change. There was a significant improvement in the functional independent measure in cognitive domains, but not total score. And on treatment analysis, there were no significant changes in functional motor scores. Okay. So when we're diagnosing, this study, it was a randomized control trial of stroke and TIA at five hospitals in the US affiliated with Yale and Indiana University. They had a treatment duration of one year, hospital and then home. OSA was diagnosed by an unintended type two study. The OSA threshold was greater than five and they were treated with auto CPAP. There were three groups, the control group who had usual care, they were neither dissuaded or discouraged to seek sleep study during the one year. And they received the type two study at the end of the one year. OSA was treated with APAP using standard intervention. And then there was an OSA treated with APAP using an enhanced intervention. So this is a, you can read the description here about what the standard intervention entails, what the enhanced intervention entails. The enhanced intervention is very, very intricate. And so if we looked at average APAP use on nights use and average percentage of nights use, there was no improvement in adherence with this enhanced intervention. So there was no significant difference in hours used or proportion of the nights use, which is reassuring because in the real world, it's very hard to kind of follow this enhanced intervention. So especially in difficult, very busy sleep medicine practices. And so this is the breakdown of the randomization in terms of the control group, the standard group, and then the enhanced intervention group. And if you, they did two types of analyses. They looked at an intention to treat analysis where patients were as randomized, all patients. And then there was no significant changes in modified Rankin score and NIH stroke scale. And then they did the as treated analysis where the three groups were defined by their APAP use. So people who had no APAP use, some APAP use or good APAP use. And so, and then they also looked at the, if you look at the, you know, the comparison of the no APAP use versus the good and the none versus the some are good, increase in APAP use was associated with improvement and modified Rankin score and NIH stroke scale score. So that was a very interesting finding. Okay. So this was the effect of CPAP on prognosis after ischemic stroke. And this was an observational study in Luzon, Switzerland of acute stroke. Patients were admitted to a central hospital and they had a three-step protocol. They did the stop bang. And if they were positive, then a home sleep apnea test. And if that was positive, then a PSG. And then auto CPAP was offered to all patients with an AHI greater than 15, and they were treating moderate to severe OSA. And the auto CPAP follow-up was at one month, three months, six months, and one year. Good adherence was typical for four hours a night, 70% of night. And functional outcome was measured at 12 months using the modified Rankin score. And this is what a modified Rankin score is, just so that you're aware of it and you can review this. And so for those with higher NIH stroke scale score at seven days reflecting worse stroke disability were associated with lower CPAP adherence. And at one year after stroke, good outcome was higher in the CPAP treated group. And the difference between modified Rankin score before stroke and one year after stroke was not significantly different between the CPAP adherent and the CPAP non-adherent group. Okay. And so this was another kind of Kaplan-Meier survival curve here where we're looking at survival probability and event-free survival and looking at the three groups, the ones without sleep disorder breathing, the ones who are with sleep disorder breathing on CPAP and the ones with sleep disorder breathing on CPAP. And so there was a dose relationship with CPAP hours and recurrence and mortality. So it appeared that hours of use really did matter. Okay. So we're at the 35 minute mark. I'm gonna go on to a few more slides. So we know that hours of use matters, but we know that there is a dose response effect of CPAP use but that CPAP use declines with time. And this was clearly shown with a retrospective study of 190 patients who were referred to a sleep clinic in Canada. So, you know, you could see that the percentage of patients continuing CPAP, any use, just declines with time. Okay. So this was a study by Cote et al in stroke in 2019, was a prospective study of 90 stroke patients undergoing inpatient rehab. OSA was determined based on data from a three-day, three-night auto CPAP download using the criteria listed here, mean CPAP pressure greater than five with a minimum average use of three hours per night and a residual AHI greater than or equal to five in any of the three nights. And they looked at, they tried to address three areas, CPAP tolerance. So there was this adherence program addressing three areas, CPAP tolerance, motivation and support. And so CPAP tolerance, the nurses and therapists and technologists had a process of device adjustment, mask changes, motivation, patients watched testimonial videos on CPAP and stroke recovery, face-to-face meetings. And then the support, there were nightly visits by respiratory therapists, tailored written feedback, weekly phone calls. And so 90% or 90 were enrolled, 70% at OSA, 84% chose to continue auto CPAP after the inpatient rehab discharge. And so after 90 days, the average nightly use was about four hours. Average use was about five nights per week with a residual AHI of six. And so after controlling for length of inpatient rehab stay, the predictors of 90-day adherence were stroke scale, aphasia and race. And so APAP adherence group also showed improvement in 90 days on the cognitive and functional components of the functional independence measure. And so this is the change in NIH stroke scale in the adherent versus the non-adherent group. Okay. And so I think, okay, I have time. So let's, this was a study, a Japanese study in 2019, a retrospective study in a Japanese rehabilitation ward, over 400 patients. They had a subacute stroke, the HST testing on the rehabilitation ward with a type three device, less than 90 days after stroke onset and less than four weeks from the time of admission to the ward. 17% had a failure rate despite being on the ward setting. So it shows you that these home tests can have high failure rates. And in Japan, the national health insurance covers CPAP when the REI is only over 40, which is high, or the AGI is over 20 on PSG. So when the REI was less than 40, but greater than 15, they had a PSG. And so if you look at the prevalence of sleep disordered breathing, at a threshold of five, it was 87%. At a threshold of 10 was about 65%. And at a threshold of 30 was about 15%. And so they looked at the activities of daily living using the functional independence measure, which is described on the right. And the REI was not an independent explanatory variable for functional independent measure score at discharge after you adjusted for several factors, including FIM score at admission. Patients were provided auto CPAPs, which were an older model. And the rehabilitation physician set the pressures. 19 continued the auto CPAP after discharge. And there was good adherence in about 17 out of the 19 patients. Okay. This was a study out of India with about 680 patients. And this was a randomized controlled trial for PAP in OSA. And you could see the breakdown in the randomization. There was some crossover from the APAP group to the non-APAP group. And so there were significant findings at one year follow-up here. You could see that there was an improvement in the modified Rankin score from comparing the CPAP group to the non-CPAP group. But in terms of vascular events, there was no significant change. This just came out. This was a meta-analysis of CPAP adherence, how it reduces stroke risk and moderate to severe OSA. This came out maybe just a few weeks ago. It was a data up to 2019. 13 studies were included, nine randomized trials, four cohort studies. There was no significant difference between CPAP and control groups for hypertension, diabetes, et cetera. And there was some heterogeneity of the baseline OSA and follow-up. So six out of the nine randomized trials and two out of the four cohort studies considered only of patients with moderate OSA and the follow-up duration varied. Good adherence was defined as we previously defined it and was reported in not all the studies. And in the cohort studies that reported good adherence, those with poor adherence were transferred to the control group. And so if you look at the forest plot of stroke risk reduction in the cohort studies, the pool's odd ratio is about 0.59. So the cohort reveals that significant stroke risk reduction at a P value of 0.04. But there was not enough for a subgroup analysis based on mild to moderate or severe. And so this is the data that we have. So this is the stroke risk reduction in the randomized control trials. The pooled odds ratio being 0.9. The overall, the randomized showed no significant stroke risk reduction, but it was heavily influenced by that one study we mentioned, the SAVE trial in 2016. But if you broke it down by good adherence versus not good variable adherence. So if you broke it down, the good adherence group showed significant stroke risk reduction. And so adherence to CPAP seemed to be really crucial to the effectiveness here. So if you break it down, you can clearly see on the top, there's a benefit. And so this study just came out. Okay. There've also been a few interesting studies about sleep duration in stroke. And so we'll go through those quickly. So this was a meta-analysis of 16 studies. So seven hours of night was set as the reference category to calculate the relative risk and 95% confidence interval of stroke under different sleep durations. And so if you could see here in these graphs, there's a non-linear association between sleep duration and total stroke, between sleep duration and fatal stroke, between sleep duration and non-fatal stroke. So longer sleep duration significantly increases the risk of fatal strokes, non-fatal strokes and total strokes. And so another interesting study stemming from a communicable disease population study in China, there were two components, a cross-sectional study and a cohort study. And they were looking at assessing daytime napping and average nighttime napping with the questions as listed. And you could see here, like if you look at the odds ratio of stroke from the cross-sectional study, and then you look at the cumulative risk over study time, there was increased risk of stroke when your nighttime sleep duration was less than seven hours or greater than nine hours, particularly greater than nine hours. And if you had a daytime napping of more than one hour, you could see that big bar at 9.03 odds ratio, that's the biggest risk. And if you look at the hazard ratio of stroke from the cohort study, the hazard ratio being that instantaneous risk over study time, you could see that at less than seven and greater than nine total sleep duration. And then if you look at the greater than one hour, you can see the daytime nap duration. The greatest risk was more than nine hours of nighttime sleep duration with a greater than one hour daytime nap duration. Okay. So those are, that's pretty much the whirlwind tour of the recent stroke literature. Over the past two, three years, there's been an avalanche of data. And so I was able to go through some of that with you, and I'm happy to answer any questions that you may have. Okay, well, thank you, Dr. Hoke. If you have a question you would like to ask Dr. Hoke and are in full screen mode, you'll need to exit full screen mode to access the ask button to submit a question. So we'll jump into a couple of questions for you here. So the first question I have is, why would there be increased risk of OSA post-TIA if there is no permanent damage? Is it an association only? So could you repeat that question? Yeah, so it's a two-part question. The first part is, why would there be increased risk of OSA post-TIA if there is not permanent damage? Yeah. And so that's an interesting question. Most likely, those patients who are having the transient ischemic attacks still have a lot of comorbid conditions. And so that may be a function of just their underlying cardiovascular and obesity, their diabetes, just their upper airway collapsibility in general. And yeah, even if the transient ischemic attack resolved, they still have those comorbid factors. And maybe it didn't completely resolve. Maybe there is still some residual damage or residual effect, even though you're supposed to have no residual deficits in motor components afterwards. But there may be residual airway components that we just can't really appreciate other than through diagnostic testing. But that's a great question. That is an excellent, excellent question. And then they also wanted to know on that same question is, is it an association only? I believe so, yes. All right, and then our next question is, did one of your studies at the beginning show what percentage stroke patients are screened for OSA? Okay, so let me, what percent, let me see if I can, I'm gonna share my screen again. Okay, okay, so what percentage patients were screened for OSA? So let me go here. So yeah, the studies by the University of Michigan groups really showed that it's not very, it's not very common. Like here, pre-stroke, you could see the numbers here, 10% were asked about snoring, 17% were offered sleep studies. It's very low, it's very low. And these are competent providers, but it just, it doesn't appear that it's on the radar for a lot of people. Even though in the popular media, sleep apnea has, you know, as we, you know, you read articles in the popular media about sleep apnea. For some providers, it just hasn't reached, you know, the top line of things that they're concerned about. And so maybe as a field, we need to do a better job of spreading the word, spreading the gospel that listen, this is important and that we need to be screening for it. Gotcha. And then they also wanted to know if you were aware of any national average with that. In terms, this is the best study. These are the best, the Michigan studies are the best ones because they looked at large numbers of people, but not across the country. But if you, like, I would suspect that these are pretty representative though. I would suspect that they're pretty representative. Great question. Great question. All right. And another one for you here. Do you find more and more of your medical colleagues using stop bag over stop bang in screening for OSA? Absolutely. Because, you know, I'll be honest, you know, and I don't know for dentists, do you folks use the stop bag? Like, do you, are you using, like checking for neck circumference? You know, we in the clinic, we don't typically check neck circumference. We're not, you know, we don't get the tape measure because you have to have disposable tape measures so you don't have infection risk. And especially nowadays we're doing telehealth. So we're not, you know, doing that anymore. So yeah, you know, the stop bag, you know, we, you know, we wanted to use the stop bang and we put it on our referral forms, but, you know, almost nobody ever puts the neck circumference down. So it's good to know that the stop bag is an option. Gotcha. And do you feel that that will be replacing the stop bang in the future? I think so. You know, this study by Katzen in 2016, you know, it's 2016, it's four years old and it didn't catch on like it should have, I think. But I think it probably should because it's a really well done study. I believe it's out of Cleveland Clinic and it shows, you know, the difference. And even with, like, even if you tried to add certain, you know, even if you added oximetry to it, yeah, oximetry helps a little bit, but, you know, the stop bag alone does a good job. Gotcha. Hold on, let me. Great questions. Really, really good questions. Let me pull some more up here and scroll down a little bit. Hold on. And I know that I rely on our, we have dentists in the community who are really hip to the idea of sleep apnea and they scream, they scream for it and they send us patients to be tested. And so it's important. And another question here for you. Why would your risk of stroke increase with more sleep greater than nine hours? What if you sleep that long and don't have OSA? Yeah, you know, it's, you know, that's true, that's true. But, you know, this study, this study from China, you know, didn't really take into account sleep apnea. But what if, you know, you're sleeping that long because you have, you know, sleep apnea could do one of two things, right? It could fragment your sleep so much that you're just not able to maintain sleep. So you're having to wake up and you get up. So it's kind of leading to an insomnia, the insomnia phenotype. But there's another phenotype beside the insomnia phenotype. That's the excessive sleepiness phenotype of obstructive sleep apnea. And if your sleep apnea is so bad that no matter how much sleep I get, I need to sleep nine hours, then that could account for that. And so there's probably components of both. And in Asians and in Chinese, I know in Indians and Chinese people, the risk of sleep apnea is high, independent of body mass index. And so that's what I think we're seeing here. And especially with the, you're sleeping nine hours and you're getting more than a one hour nap per day, that's a lot of sleep per day. And you could see how the hazard ratio goes up. And so this, you know, and same with the odds ratio. So the odds ratio being the cumulative risk, the hazard ratio being the instantaneous risk. And so you could see that, you know, the risk is there. And I suspect it's probably underlying sleep apnea, but could it be underlying other disorders too? Absolutely, there are other disorders that can account for excessive daytime sleepiness. Not just central disorders of hypersomnia like idiopathic hypersomnia and narcolepsy, but just if you're metabolically in bad condition, it can account for some of this. Great, and then we're gonna have one more question for you here. Yeah, these are great questions, great questions. With the strong significance of ODI as a predictor of OSA, can you comment on the need to do a full PSG or HS, or HSAT, keeping in mind that AHI is not the best measurement of disease. Has any research been done on C-reactive proteins and stroke? Yeah, you know, plenty of, you know, we don't have a biomarker yet for stroke. You know, we would love to have one, but we don't. You know, like a blood test that we could do for stroke, because we know that, listen, it's hard to get people to come into sleep labs. And we know that insurance providers are very reluctant to pay for in-lab studies nowadays. So the volume of in-lab studies is decreasing. And as a result, more people are getting home sleep apnea tests. But even now there's a backlog in home sleep apnea tests, especially with COVID. Can you get disposable home sleep apnea tests? Can you, you know, it depends on availability. People have to drive to the sleep center to get the home test, bring it back home, wear it and drive back and give it back. And so, you know, if we could, you know, I think that, you know, oximetry to identify moderate to severe sleep apnea is, I think it's useful. I think it is useful. Now, the problem is that, yeah, it probably does, it is probably pretty effective. Like if you look at these receiver operating characteristic curves, right? We know that the ODI is pretty good at predicting the REI, but getting the machine afterwards is the problem because the insurance companies are, again, are the hurdle in terms of getting the machine. If they're not willing to pay for the device, the CPAP machine, then, you know, then we're kind of forced to get the home test. Dr. Hoke, can you explain why greater than nine hours was more risk? I think like we, I tried to explain it, you know, I suspect it's comorbid conditions and untreated sleep apnea being primarily the ones and then, and being the hypersomnia phenotype of untreated obstructive sleep apnea. That's my suspect, my suspicion. And then the, this other question here is, philosophically speaking, why isn't there more awareness of OSA among doctors treating stroke patients? That is a great question. You know, it depends on institution to institution, you know, the Academy of the American Heart Association and the American Stroke Association, like in those first couple of slides, they, you know, put out this recommendation, but, you know, you know, I don't have a good justification for that, you know, and it's one of the few things that we can actually treat and fix, you know, it's one of like, you know, like as neurologists, we defer stroke prevention to primary care in terms of hypertension, cholesterol, diabetes, weight. The sleep apnea is something that actually is very fixable. And, you know, it's hard to fix blood pressure. It's hard to fix cholesterol. It's hard to make diabetes go away. It's hard to get the BMI under 30, but we could treat the sleep apnea. And that's maybe the one real treatable thing that we can fix to decrease your stroke risk. And so I think it's institution to institution. We're trying to spread the word as much as we can in neurologic societies. And I think the word is spreading, like at Emory, they're very into it. One of our biggest referrals for sleep medicine evaluations is from our stroke clinic. They know, and that's a big chunk of our referral base. So maybe we could take some of your slides and kind of spread the word too in our own communities. Yeah, absolutely. Please feel free to use it. And you can always email me. My email was on the first slide. If you have any questions or concerns or any other things you want to talk about, I'm available. Okay, we got two more questions for you here that I'm seeing. So last call, if anybody has any other questions, I don't want to miss them there. But the Brevetta study showed no improvement in CPAP wear with enhanced intervention, yet other studies show that follow-up is the only factor that improves wear. You know, it's, you know, but the standard intervention here, it's five in-person and one telephone visits per year. So they did have intervention, you know, it wasn't like they didn't do anything, you know, but the enhanced intervention was really above and beyond like education session at the time of the study, assessing attitude, beliefs, social supports, individual risks, then at week one, they had one in-person visit and two telephone calls, weeks two to four, weekly visits, months two to 12, two in-person visits and seven telephone, that's a lot. You know, it's hard for providers. You know, I know in my practice, I can't do this. I can't do it. I don't have the bandwidth to do this. You know, even if I'm working 24 hours a day, I couldn't do this. And so the standard intervention works, but there has to be intervention. There has to be something. And then another question for you here is, you just qualified the difficulty of patient follow-up in busy sleep medicine practice. Isn't the primary purpose of sleep medicine practice follow-up for compliance? Yeah, and we do that, but you know, but this level of follow-up is, you know, absolutely. You know, I follow up my patients frequently, but can I follow them up in a way but can I follow them up two telephone calls in the first week, weekly visits for the first month, two in-person visits and seven telephone visits over the next, over the course of the remaining one year? I honestly don't know if there are providers who have enough room in their schedule to do this sort of thing. I honestly don't know. And if you can, that's great. You know, that's fantastic. But I know that I'm seeing a lot of new patients and I'm seeing a lot of follow-ups for a lot of people. And so I know that my schedule is full. And so I do try to get my patients in as frequently as I can get them, especially if they're not doing well. If they're doing well, then you can space it out more. But if the adherence is poor, yes, absolutely. In that first couple of months, you definitely want to follow them up as frequently as you can. Yes. So you would say- And I think really that is why we have such a good partnership with doctors like you. Yeah, absolutely. And I think we all understand the difficulty of keeping patients with compliant, keeping patients compliant, whether it's CPAP or mandibular advancement therapy. Yeah. And, you know, honestly, most of my patients are adherent. Very few are not adherent. And so it's, you know, because what happens is that people get devices and then get sent out to the wind and then they never get seen by anybody again. Those are the ones who do badly, you know? So if you have some measure of follow-up, however you define it for yourself and your practice, those patients do well, just from my clinical experience.
Video Summary
Thank you, that was excellent. I think that summarized the transcript of the video very well.
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