Sleep Technology

As the research on sleep and circadian timing expands, more research-based resources have been made available to the general public. Here, I share two of these online resources with links to research to improve general understanding of these tools and how they have been used in sleep and circadian science.

Resource 1: The Psychomotor Vigilance Task (PVT)

It is well known that sleep loss and circadian misalignment (i.e. when your underlying circadian clock does not match your desired sleep-wake schedule) negatively affects attention. And attention is critically important for many of our everyday tasks, both work and non-work related. These attentional deficits range from lapses in attention to increased reaction times, and can even lead to catastrophic accidents, including car accidents and work-related injuries.

The Psychomotor Vigilance Task (or PVT) is the premier tool for measuring the effects of sleep loss on attention. And performance on the PVT can show both sleep-loss related impairments and normal fluctuations in attention based on circadian timing. So, it is an ideal tool for individuals to use to understand their changes in cognitive ability based on sleep and time of day.

Up until recently, the PVT was only available in certain software programs, and was a 10-minute task, making it difficult for the general public to access and use. Today, it is available in a 3-minute mobile format via the App Store so that it can be used more broadly, thanks to researchers at Texas A&M!

To best use the PVT, it is ideal to first get a baseline measure of performance. For example, how well do you perform during the most productive and most awake hours of your day? Once you have established this baseline performance, the PVT can be used to measure changes from that baseline. For example, how much worse do you perform after a night of poor sleep? Or when you normally should be sleeping (imagine pulling an all-nighter or working a night shift)?

To access the 3-minute mobile PVT, use this link: https://apps.apple.com/gb/app/pvt-research-tool/id1475726298

Here are some publications on the PVT:

3-minute smartphone-based and tablet-based psychomotor vigilance tests for the assessment of reduced alertness due to sleep deprivation (https://pubmed.ncbi.nlm.nih.gov/27325169/)

Ultra-short objective alertness assessment: an adaptive duration version of the 3 minute PVT (PVT-BA) accurately tracks changes in psychomotor vigilance induced by sleep restriction (https://academic.oup.com/sleepadvances/article/3/1/zpac038/6764767)

Fitness for duty: a 3-minute version of the Psychomotor Vigilance Test predicts fatigue-related declines in luggage-screening performance (https://pubmed.ncbi.nlm.nih.gov/21912278/)

Fitness for duty: a 3-minute version of the Psychomotor Vigilance Test predicts fatigue-related declines in luggage-screening performance (https://academic.oup.com/sleep/article/44/11/zsab151/6301496)

Resource 2: Circadian Phase Calculator

Our circadian rhythms, or 24-hour biological cycles, determine much of our behavior and biological functioning, from hormones, to attention and performance, to sleep and wake times. However, researchers have found that it is very difficult to measure circadian rhythms effectively. This is because the “gold standard” measure for measuring circadian timing is “Dim light melatonin onset” (or DLMO). DLMO is the natural change in melatonin levels indicating when the body thinks it is night (i.e. time for sleep; high melatonin), or day (i.e. time for wake and activity; low melatonin). Typically, DLMO marks the time when the body is preparing for sleep, and is about 1-2 hours before bedtime is ideal. DLMO is best measured in a lab under very strict conditions where saliva, blood, or urine samples are collected hourly.

However, with recent innovations and technology from researchers at Henry Ford Health and Arcascrope, a new online platform is available to help predict DLMO using activity and health data from an Apple watch, Fitbit, etc. Using a proprietary algorithm, the online resource calculates your personal DLMO based on each day’s data.

With this tool, anyone can better understand their current circadian rhythm, by understanding when their body is naturally preparing for sleep, and whether or not that timing is ideal for your ideal bedtime or work schedule. There is a bright future in implementing these tools to help people better adjust to their lifestyle, whether it concerns cross time zone travel, shift work, or adjusting to a new lifestyle or schedule. By understanding your current DLMO and where you want it to be ideally, it becomes easier to figure out when to use bright light or avoid bright light, when to try to go to sleep or when to take up, etc.

To access this online resource, use the following link: Phase Calculator (predictdlmo.com)

You can also read the following peer-reviewed paper to learn more:

Predicting circadian misalignment with wearable technology: Validation of wrist-worn actigraphy and photometry in night shift workers (Predicting circadian misalignment with wearable technology: validation of wrist-worn actigraphy and photometry in night shift workers | SLEEP | Oxford Academic (oup.com))

Post written by: Dr. Elle Wernette

PhD in Cognitive Neuroscience; Sleep and Circadian Science Researcher & Instructor