Our work with wearables
The first, and most well-established, source of health data comes from monitoring sleep and physical activity patterns using a trusted consumer wearable device. This method gives you substantial insights into your sleep and activity levels, and the tools provided allow you to enhance both.
Our findings here show how we’ve validated these methods specifically in Singapore.
Wearable sleep trackers can rival or exceed the performance of ‘research actigraphs’ costing up to 3-5x more in assessing sleep timing, duration, and regularity. This finding affects the type of sleep tracker research groups purchase for long term ambulatory measurement of sleep.
One of the sources of inaccuracy in sleep measurement relates to misclassification of periods of quiet wakefulness as sleep. The team devised a protocol to test this in a realistic manner that should be incorporated into future testing protocols. We showed how this protocol can be used to differentiate better quality and lower quality trackers. This testing protocol can / will be used by future researchers seeking to evaluate in wearable sleep trackers in realistic settings.
However, there are caveats: on average, their accuracy falls with user age and with persons with less efficient sleep (either longer sleep latency or greater wake after sleep onset). This finding is of practical importance to persons who take sleep tracking seriously.
We showed how the PPG waveform signal, changes according to sleep stage, reflecting greater parasympathetic influence at work during N3 compared to light sleep and REM. The waveform recorded in N3 is also associated with measures that correspond to relatively lower arterial stiffness. This provides additional evidence of the benefit of N3 duration.
Not all ‘consumer wearables’ are comparably accurate. The low-cost OEM devices made by putting together sensors and off the shelf algorithms without evidence for testing or refinement, perform poorly.
For characterizing sleep regularity, we used large scale data from HPB’s HiSG study to show that observation periods longer than 1 week (up to 18 days) are necessary to achieve ~80% confidence in assessing sleep regularity.
More studies from our lab that characterized sleep patterns using wearables and their links on physiology, wellbeing or health
Valuable longitudinal cross-cultural information about sleep patterns can be derived from harnessing these devices at scale. Sleep in East Asians, beyond being merely shorter in duration, is less efficient and more variable, particularly on weekdays. Asians have less sleep extension over weekends. Significant differences in work culture may be driving these differences rather than biology or latitude differences.
Singapore was one of the few countries where a large group of adults had objectively tracked sleep habits before, during and after COVID-19. In this study, working adults kept their pre-COVID-19 sleep routines even after the announcement of the global pandemic. These routines were demonstrably altered by New Year and Lunar New Year celebrations / festivities but what was to be the most severe pandemic the world has encountered did not shift routines until citizens underwent movement restrictions. This illustrates how difficult it can be to shift sleep habits without structural measures.
We showed how midsleep timing during the COVID-19 pandemic became later globally reflecting later bedtimes and waketimes (through a collaboration with Oura Health OY). This reflects a global preference for later bedtimes than what is historically regarded as normative, likely reflecting the influence of ready means of communicating with and being engaged by large scale electronically enabled social networks.
Alongside post COVID-19 re-opening, we found a restitution of physical activity in young adults and a return to earlier sleep, but also earlier wake times and a shortening of sleep duration in workers who return to office compared to those who continue to work from home. These findings have relevance to planners seeking to evaluate the merits and demerits of working from home.
Night by night variability in sleep duration has a significant effect on next day (but not next, next day) mood, motivation and sleepiness. This lends credence to the issuance of ‘readiness’ scores by consumer wearables. The work also supports the value of sleep regularity in giving better scores on these three markers of wellbeing.
There is much evidence that poor sleep increases the risk of diabetes mellitus. Part of the difficulty persuading young people to sleep better is their subjective sense of invulnerability to unhealthy sleep. This feeling is not totally unfounded as we found that university undergraduates to have normal nocturnal and daytime glucose profiles as well as normal insulin responses to glucose challenge despite sleeping an average of ~6hrs a night i.e. below what is recommended.
We demonstrated a method to obtain within 5mm/Hg MAE quality blood pressure measurements using a random forest ML algorithm trained on finger-tip photoplethysmography data. This work opens the door for seamless high frequency sampling of nocturnal blood pressure using wearable sensing that is comfortable. Note that current implementations like those used by Samsung using oscillometry require user action to obtain a reading.
This study was initiated as a collaboration between NUHS and the Sleep and Cognition Laboratory at the Yong Loo Lin School of Medicine to understand the impact of different shift schedules on sleep, health and well being. Using 8-weeks of wearables/mobile tracking, we found that medical interns on night-float schedules show more regular and better-quality sleep, and less negative outcomes for mood, motivation and cognition than a 24h overnight-call schedule. On-shift napping benefitted cognition.
Microsites featuring more of our work
Need for Sleep is a series of sleep research camps for teens in Singapore to investigate the relationships between restricted sleep, health and cognitive outcomes in adolescents. ​
This study was initiated as a collaboration between NUHS and the Sleep and Cognition Laboratory to to understand the impact of physicians overnight call schedules, their challenges and how schedules can be optimised for cognition, health and well-being.
Check out our body of work on how napping benefits cognition and wellbeing!