Need assistance?
By Sree Roy
Sleep data collection usually represents a fragmented snapshot of a person’s typical experience. Foundational tools like single-night in-lab polysomnography and retrospective self-report questionnaires do not account for night-to-night variability or for sleep’s nuanced relationship with other behaviors.
Increased adoption of wearable technology is changing this dynamic, allowing researchers to analyze multiple dimensions of sleep health (for example, duration, timing, regularity, and quality, to varying extents), along with wake activities, over extended periods in users’ natural environments.
In fact, wearables are a key focus of a recently renewed collaborative partnership between Monash University and Brigham and Women’s Hospital. The international alliance between Australia’s largest university and one of Boston’s largest hospitals, now in its seventeenth year of sleep and circadian research, aims to leverage mobile health technologies to bridge basic sleep physiology, clinical trials, and public health policy.
“Wearables allowed us to recognize that sleep is not something that happens during night hours and then that’s it,” says Emmanuel Stamatakis, PhD, director of Brain Park at Monash University’s Turner Institute for Brain and Mental Health. Rather, sleep is acknowledged as part of a 24-hour day.
“The advantage of wearables is they’ve popularized that idea of living whole lifestyles because most trackers capture in great detail all behaviors including posture (eg, standing, sitting), sleep parameters, and physical activity parameters,” Stamatakis says, “and they attempt to somehow wrap them into one package and support lay consumers to improve their behavior.”
Synergy with Sleep
Because wearables can estimate sleep duration with reasonable accuracy while simultaneously tracking physical activity, researchers can measure the small day-to-day changes that questionnaires invariably miss, making it possible to study how sleep interacts with other lifestyle behaviors—and how those interactions influence long-term health. “Questionnaires have a lot more measurement error noise [than objective wearables], so they misclassify behavior and do not allow us to estimate relatively small increments.”
Monash-Brigham researchers are discovering that sleep may have a greater impact on health when considered alongside other daily behaviors rather than in isolation.
Epidemiological studies consistently show that relatively small improvements across sleep, physical activity, and diet can work together to produce meaningful health benefits. Adding just 5 to 10 minutes of sleep per night, 2 to 4 minutes of moderate-to-vigorous physical activity per day, and about half a cup of fresh vegetables daily is associated with an approximately 10% reduction in the risk of major adverse cardiovascular events over seven to eight years.1
The combined effect appears to be greater than the sum of its parts. Achieving a similar reduction in cardiovascular risk through any one behavior alone would require substantially larger changes—for example, roughly 30 additional minutes of sleep per night. “There seems to be a synergy,” Stamatakis says.
That distinction is important because sustained behavior change is notoriously difficult. “It may sound modest. It’s not modest at all. Health-related behavior is very difficult to change,” Stamatakis says. Identifying the smallest changes that still produce measurable health benefits could make public health interventions more attainable.
This objective measurement also provides a more precise basis for behavior change. While subjective reporting remains valuable for understanding a patient’s experience, wearables provide tangible markers that can be used to coach patients toward improved health habits.
Sleep Regularity Index
Wearables have also helped elevate another dimension of sleep health that until recently received far less attention than duration: sleep regularity.
“Over the past few decades, we have increased our understanding that sleep has multiple dimensions that influence health,” says Shantha M.W. Rajaratnam, PhD, head of the Monash School of Psychological Sciences and co-leader of the Monash-Brigham collaboration. “What early work done at the Brigham—and expanded through the collaboration at Monash—showed was that sleep regularity is an independent and important health metric.”
Much of that work was led by Andrew Phillips, PhD, an Australian sleep and circadian researcher who trained at Brigham and Women’s Hospital, later established a faculty position and research program at Monash University, and more recently moved to Flinders University. Phillips and colleagues developed the Sleep Regularity Index (SRI) at Brigham and Women’s Hospital, which measures how consistently a person is asleep or awake at the same time on consecutive days.2
Continuous wearable monitoring made the metric possible. In a collaborative, cross-institutional study using more than 10 million hours of accelerometer data from nearly 61,000 UK Biobank participants, Phillips and colleagues showed that sleep regularity was a stronger predictor of all-cause mortality than sleep duration alone. Participants with the most regular sleep schedules had substantially lower risks of all-cause, cancer, and cardiometabolic mortality than those with the most irregular sleep schedules, independent of how long they slept.3
The findings have since been reinforced by additional epidemiological studies linking irregular sleep patterns to cardiovascular disease, diabetes, dementia, and other chronic conditions.
“This comes purely from the capabilities that wearable devices permit,” says Stamatakis. “It wouldn’t have been possible to develop the Sleep Regularity Index without the UK Biobank and the richness of data that wearable devices provide.”
For Rajaratnam, the work illustrates the value of long-term international collaboration. “The partnership between Monash and the Brigham really gave rise to a significant program of work around the role of sleep regularity in influencing the risk of a range of diseases—from cardiometabolic to neurocognitive to mood disorders,” he says.
Research Versus Consumer Wearables
Despite the proliferation of wearable devices, a divide remains between research-grade and consumer-grade technology. Research-grade devices, typically triaxial accelerometers, are valued for their transparency and validated algorithms. However, they often lack the multi-sensor capabilities found in modern consumer smartwatches and rings, such as photoplethysmography for heart rate, pulse oximetry, and temperature sensors.
Consumer-grade devices are more technologically advanced and user-friendly, leading to higher long-term usage. The barrier to their use in rigorous academic research is the proprietary nature of their algorithms. “By not making the data processing algorithms transparent, it is very hard to use them [in scientific research] because the consumer-grade wearables become black boxes,” Stamatakis says.
Some manufacturers have begun to cooperate by making raw, unprocessed data available to researchers, a move Stamatakis describes as highly desirable. Access to raw signals would allow researchers to apply standardized, transparent algorithms to the more advanced sensor suites found in consumer devices, potentially enabling more accurate sleep staging and physiological monitoring at scale.
Also, while wearables have moved beyond actigraphy only, gaps still exist. Distinguishing between quiet rest and actual sleep remains a challenge, as does the detection of short daytime naps. Furthermore, while consumer devices claim to measure sleep stages, the validity of these measurements compared to gold-standard polysomnography is a subject of ongoing validation.
Open-science projects like The Wearable Landscape and Open Wearables are working to standardize validation and data interpretation processes. Available at wearable-landscape.info/vision, The Wearables Landscape is building a centralized platform and interactive dashboard to pool validation studies and research protocols for 24-hour physical behaviors, including sleep. While at openwearables.io, developers launched a platform to unify wearable health data through an artificial intelligence-ready application programming interface.
Global Public Health Implications
The data generated by wearables is expected to influence the next generation of public health recommendations. Current guidelines, such as the Physical Activity Guidelines for Americans and World Health Organization guidelines, have historically focused on exercise and sedentary behavior.
Future updates are likely to incorporate sleep into a more holistic 24-hour framework, predicts Stamatakis. They will likely include more sophisticated recommendations on sleep regularity and timing, moving beyond the basics of simply getting seven to nine hours.
Rajaratnam envisions wearables playing a key role in the implementation of these policies. “A wearable is able to quantify multiple dimensions of sleep health, as well as getting to what a person’s current sleep debt is, which is reflective of the night before but also of her recent sleep history over several days or weeks,” he says. “That’s why I think these wearables offer us a really significant opportunity in public health policy implementation.”
The collaboration driving much of this work continues to expand. Co-leader of the Monash-Brigham collaboration Charles Czeisler, MD, PhD, chief of the division of sleep and circadian medicine in the Department of Medicine at Mass General Brigham, says the partnership has evolved from a small faculty exchange into a jointly funded international research program supported by a five-year Wellcome Trust grant. “It’s been exciting to see how the initiative has grown from just a few scholars in the exchange to now a steady drumbeat,” he says.
The work is also becoming more global. Most wearable-derived sleep evidence comes from high-income countries, even though most of the world’s population lives in low- and middle-income countries. Differences in climate, culture, work schedules, and socioeconomic conditions may all influence how sleep affects health, making it important to expand research beyond Western populations.
Initiatives such as the Prospective Physical Activity, Sitting and Sleep (ProPASS) consortium are helping address that gap by providing research teams in underrepresented regions, such as Malaysia, Chile, and Mexico, with wearable devices, standardized methods, and training.4
For Czeisler, Rajaratnam, and their colleagues, the goal extends beyond helping individuals better understand last night’s sleep. By capturing sleep continuously, objectively, and alongside the other behaviors that fill a 24-hour day, wearables are enabling researchers to rethink how sleep influences health across populations—and how modest, measurable changes in daily routines may help prevent chronic disease.
Top image: At Monash University, Trish Emperado, PGDipMedTech, the Edwards Lab manager and project coordinator, sets up a sleep study for Georgina Rawson, a PhD Candidate in the Edwards Lab. The ceiling lights allow for the testing of the impact of light wavelength and brightness on circadian rhythms, as well as select functional outcomes.
17 Years of International Synergy: The Monash-Brigham Collaboration
The recent renewal of the research partnership between Monash University and Brigham and Women’s Hospital marks nearly two decades of a collaboration that has produced more than 250 peer-reviewed publications. What began as a scholarly exchange has evolved into a bi-institutional program that bridges basic physiology, clinical trials, and public policy.
“I never in my wildest dreams imagined that the vision for this kind of a collaboration would expand in scope, breadth, and in terms of the number of people involved,” says Monash’s Shantha M.W. Rajaratnam, PhD. The partnership has been characterized by a fluid exchange of “boots on the ground,” with faculty and PhD students moving between Melbourne and Boston to share methodologies, clinical protocols, and multidisciplinary expertise.
Key Research Milestones
Beyond the focus on wearables, the collaboration has delivered landmark findings in several areas of sleep and circadian medicine, including:
- Circadian Regulation and Treatment: Collaborative work led to the understanding of how ordinary room light suppresses melatonin and further characterization of the dynamics of light’s effect on the circadian clock. This foundation was instrumental in studies of the melatonin agonist tasimelteon, which ultimately received FDA approval for treating circadian rhythm sleep-wake disorders.
- OSA Phenotyping and Endotyping: Researchers from both institutions, including Scott Sands, PhD, and Bradley Edwards, PhD, have pioneered work in identifying the distinct physiological traits underlying obstructive sleep apnea. This “endotyping” approach aims to move away from a one-size-fits-all treatment model and toward personalized therapies, including pharmacologic options currently in pivotal trials.
- Occupational Health and Safety: The Harvard Work Hours, Health and Safety Group, led by the Brigham but now also involving researchers from both sites, has published influential data on sleep disorders in police officers and first responders. This work has directly informed public policy, including a Massachusetts law that raised penalties for night driving violations among junior operators, resulting in a 40% reduction in fatal or incapacitating injuries among teen drivers.
- The COPE Initiative: During the COVID-19 pandemic, the partnership pivoted to assess the impact of stay-at-home orders on mental health (as well as several other aspects of health). The resulting research, published in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report, was cited in a presidential executive order to release more funding for mental health services.
Charles Czeisler, MD, PhD, notes that the collaboration’s reach is a unique asset. “Monash has a tremendous global reach… the international aspect of it, and so, I believe in the Monash-Wellcome Trust-Brigham Project, we have taken advantage of their campuses in Malaysia and a number of other countries,” Czeisler says.
As the partnership enters its next phase, the focus remains on translating scientific discovery into scalable digital health solutions. Emmanuel Stamatakis, PhD, emphasizes the importance of this continued synergy: “Jointly we can really provide some huge momentum to this very exciting field.”
—Sree Roy
References
- Koemel NA, Biswas RK, Simpson SJ, et al. Combined variations in sleep, physical activity, and nutrition and the risk of major adverse cardiovascular events. Eur J Prev Cardiol. 2026 Mar 23:zwag141.
- Phillips AJK, Clerx WM, O’Brien CS, et al. Irregular sleep/wake patterns are associated with poorer academic performance and delayed circadian and sleep/wake timing. Sci Rep. 2017 Jun 12;7(1):3216.
- Windred DP, Burns AC, Lane JM, et al. Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study. Sleep. 2024 Jan 11;47(1):zsad253.
- Stamatakis E, Koemel NA, Mitchell JJ, et al; ProPASS Collaboration; ProPASS Collaborators. Prospective Physical Activity, Sitting and Sleep consortium (ProPASS): addressing methodological and geographical barriers to inform global public health guidelines, interventions and precision medicine. Br J Sports Med. 2026 Jun 29:bjsports-2025-111283.
Photography by Leigh Henningham
Advertisement
