How objective sleep testing that lasts not just a night or two, but potentially for months or years, could improve patients’ sleep health.

By Ann H. Carlson

When it comes to precision healthcare, the more data sleep physicians can access to develop personalized treatment plans, the better. This is the philosophy behind the longitudinal sleep testing clinical model offered by Empower Sleep, a virtual, direct-to-consumer sleep practice.

Home sleep testing conducted over multiple nights (or longer), longitudinal sleep testing in clinics can clarify a diagnosis, as well as provide objective data on interventions and overall sleep quality.

“For example, if a patient has symptoms of insomnia, do they have insomnia with reduced sleep quality, or is it insomnia with preserved sleep quality?” says pulmonologist-sleep physician Sahil Chopra, MD, CEO and co-founder of Empower Sleep. “They’re both going to be managed very differently.”

Typically, Empower Sleep patients commit to a longitudinal testing model for three months, but some have engaged in nightly testing for more than a year. Since launching in 2022, Empower Sleep has collected more than 250,000 hours of contextualized, medical-grade sleep data, Chopra notes.

This means Empower Sleep clinicians and patients receive regular feedback about which interventions are working—and which are not. Chopra has found that when patients see concrete data that a treatment is working, it encourages them to better adhere to interventions such as CPAP.

“With longitudinal testing, one can provide hyper-precise care that is radically better than the standard of care,” Chopra says. “It also drives higher levels of patient engagement, education, and awareness.”

allergies sleep testing
Influence of allergies and body position on sleep-disordered breathing.
34 y/o female with a history of hypertension being evaluated for snoring.  Note how sAHI3% ranges from 3/hr to 26/hr and SQI ranges from 26 and 51.  Arrow A– Patient slept semi upright at a friends house where there were less allergens and wedge pillow. Notice the reproducible and substantial improvement in sleep-disordered breathing.  Arrow B– Patient reported an acute worsening of allergies.
Courtesy of Empower Sleep

Uses for Longitudinal Sleep Data

While nowhere near as frequently employed as one-night sleep tests, longitudinal sleep testing clinical models are growing in use.

“Relying on a single-night sleep study increases the risk of false negatives, a diagnosis as ‘normal,’ or a misclassification of the severity of a patient’s sleep apnea,” says Chelsie Rohrscheib, PhD, neuroscientist and head sleep expert for Wesper, maker of a patch-based home sleep test and sleep management service provider. “Longitudinal testing reduces this risk by allowing physicians to sample many nights of sleep and better understand what a ‘typical’ night looks like for their patient.”

The results from longitudinal testing have profound implications for precision care and treatment in sleep medicine, according to Laurent Martinot, co-founder and CEO of Sunrise, developer of a chin-patch home sleep test.

“Clinical decisions based on a single-night AHI [apnea-hypopnea index] can significantly differ from those based on an averaged AHI score from three nights, according to a recent study,” he says. “Specifically, in 19.6% of observations, the clinical decision would change if it were based on the averaged score instead of a single night’s data.1 This discrepancy indicates a substantial risk of both over- and under-treatment based on a single-night test.”

Through regular monitoring of sleep patterns, longitudinal testing also facilitates the identification of sleep fragmentation and changes in sleep architecture, Martinot adds.

Additionally, Chopra notes that longitudinal testing allows physicians to monitor treatment efficacy and adjust as needed. “If apnea indices get better for a patient starting CPAP, but their sleep quality gets worse—well, you need to think of a different solution,” he says.

cpap sleep quality
 Influence of autoCPAP on sleep apnea and lack of improvement of sleep quality.
72-year-old male with PMH of atrial fibrillation s/p ablation, hypertension, GERD, ulcerative colitis, and sleep apnea. Block A: Note on the nights without CPAP. sAHI 3% ranges from 18-20/hr and SQI ranges from 18-23. Block B: Note the marginal reduction of sleep apnea burden without any improvement in SQI. CPAP derived AHI events range from 0.8- 3.3/hour (ResMed Airview). Note the substantial difference in CPAP derived AHI and diagnostic test derived sAHI. Courtesy of Empower Sleep

For example, Chopra was recently able to significantly lower the dose of doxylamine for a patient with insomnia. “We’ve been able to objectively prove that her sleep is the same with the full dose as with a third of a tablet,” he says.

Patients can use the longitudinal data for lifestyle management.

“Longitudinal testing helps a person objectively see the impact of the steps they are taking, which may include stress reduction, mindfulness and breathing training, or improved sleep timing,” says Solveig Magnusdottir, MD, MSc, MBA, chief medical officer for SleepImage, developer of a sleep software as a medical device solution and several home sleep testing devices.

Integrating Consumer Wearable Data

Magnusdottir distinguishes between consumer wearables and medical devices designed for longitudinal sleep testing. 

“There is a big difference between sleep data that is based on measures of physiology versus estimated physiology,” she says. “Medical devices can measure sleep from either cortical brain measurements using electroencephalography sensors or through the autonomic nervous system using devices with photoplethysmography sensors worn on the wrist or finger that collect data continuously during the sleep period. Such medical information may include an objective measurement of sleep quality, reflecting health outcomes and the presence of a sleep disorder.”

Of course, patient adherence with wearable medical devices has been made easier thanks to popular consumer products such as the Apple Watch, Samsung Galaxy Watch, and Oura Ring. These products also enhance patients’ interest in their sleep patterns.

At Empower Sleep, patients use SleepImage devices for medical-grade testing, but physicians also look at data from patients’ wearables. Chopra says, “If a person exercised or did so many steps, then how did that influence their sleep?”

Sleep diagnostics and therapy company ResMed found in its 2024 Global Sleep Survey that 36% of adults globally currently track their sleep, and about a third of those respondents do so either every night (36%) or most nights (31%).2

But while collecting data wirelessly is easier than ever these days, interpreting so much data can be onerous. “Sleep medicine professionals require specialized training and access to analytical tools and software capable of processing and interpreting longitudinal sleep data accurately,” says Carlos M. Nunez, MD, chief medical officer at ResMed. “Additionally, interdisciplinary collaboration with data scientists and biostatisticians can enhance the interpretation of complex sleep datasets.”

To organize the immense amount of data it collects nightly, Empower Sleep designed in-house technology. “The data needs to be visualized in an intuitive way,” Chopra says. “We’ve had to redesign everything from the ground up for how we look at information over time.”

Reimbursement Challenges

While the technology to collect longitudinal sleep study data has become more convenient, reimbursement policies are inconsistent.

Reimbursement is primarily available through remote patient monitoring (RPM) codes for eligible patients. “For RPM to be reimbursed, the patient must use a device for at least 16 nights per month,” says Kyle Miko, CRT/CSE, founder and chief marketing officer of nationwide home diagnostics testing provider VirtuOx.

However, Miko points out that this route frequently includes a monthly copay. “As the fees would apply to the patient’s calendar year deductible, the monthly expense for the patient could be $50,” he says. “With the patient having to shoulder the expense, the concept of longitudinal sleep testing is not common.”

While payors may be slow to acknowledge the benefits of longitudinal sleep testing, more physicians and patients are coming on board.

“There is an increased awareness of the benefit of including occasional sleep testing with an intervention for a sleep disorder,” Magnusdottir says. “Given some available testing modalities that require very little effort and come at a low cost, a practitioner may choose not to require reimbursement to improve precision care.”

For example, Empower Sleep bills insurance for patient visits but not for the repeat testing. The company covers the cost of collecting and interpreting continuous data by bundling nightly testing into a monthly patient membership fee.

The fee also “allows them to get same-day or next-day visits, text their physician, have longer visit times, and have unlimited sleep testing,” Chopra says.

Of course, more widespread adoption of longitudinal sleep studies will likely be contingent on more robust reimbursement policies.

Future of Longitudinal Sleep Studies

According to Nunez, longitudinal studies are poised to revolutionize sleep medicine by offering deeper insights into sleep physiology, facilitating early detection of sleep disorders, and optimizing therapeutic approaches for improved patient outcomes.

“Future advances in longitudinal studies should include the integration of artificial intelligence and machine learning algorithms for more precise predictive analytics and personalized interventions,” he says. “Furthermore, advancements in wearable sensor technology and data analytics platforms are likely to enhance the accessibility, accuracy, and usability of longitudinal sleep data.”

Rohrscheib predicts that longitudinal sleep testing will eventually become standard in most clinics, adding that it could also supplement in-lab sleep studies for diagnostic accuracy. “As the technology continues to evolve, we will see more sleep disorders included for assessment by these technologies,” she says. 

Ultimately, the data from longitudinal sleep testing could have broader implications for a patient’s overall health. Magnusdottir envisions that longitudinal data from clinically validated sleep technologies will help integrate sleep medicine into chronic care management, including cardiovascular and brain health. “Implementing precision sleep management is likely to improve health outcomes, reduce costs, and make a significant impact on the quality of life for each patient,” she says.

In the meantime, the onus is on sleep professionals to pursue the benefits of longitudinal testing. Chopra sees this as an opportunity to work collectively to improve care, patient experiences, and the scientific understanding of sleep physiology.

“This data is actually helping us become more intelligent when it comes to taking care of patients,” Chopra says. “Longitudinal testing is not just a two-night test, but rather an ongoing journey to better sleep.”

References

1. Martinot JB, Le-Dong NN, Tamisier R, et al. Determinants of apnea-hypopnea index variability during home sleep testing. Sleep Med. 2023 Nov;111:86-93.

2. Discover your sleep super powers. ResMed. 2024. Available at https://document.resmed.com/documents/global/2024-Sleep-Survey.pdf.

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