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What is it?

Sleep duration is simply the amount of time that an individual is asleep per night. Regardless of sleep stage, this measure has been shown to be an important factor to quantify, as it directly impacts physiological and psychological parameters in both the short and long term, impacting health, performance, and longevity.

What does it measure?

Sleep duration is the total sum of time spent asleep, regardless of sleep stage, excluding time spent awake while in bed. Using combinations of heart rate, heart rate variability, breathing, motion, and pulse waveform data, approximating sleep versus awake time is possible.

Biostrap uses inputs from all of the listed measurements to estimate light sleep, deep sleep, and time spent awake; therefore, the reflected sleep duration is the sum of light and deep sleep.

Correlation with health conditions

Adequate amounts of sleep have been tied to numerous health outcomes and remains a widely-studied topic. While sleep quality has been the focus of more recent research, the total sleep duration still remains a commonly reported metric and highly correlated with health outcomes.

Sleep is highly important to regulating biological processes, allowing for adaptation, recovery, and preparation. Many repair processes occur during sleep, with surges in growth hormones and reduction in stress hormones. Physiologically, increased sleep duration has been shown to reduce stress, improve cardiovascular markers (e.g. heart rate, heart rate variability, and arterial stiffness), reduce weight gain, improve immune function, and lower risk of all cause mortality and varying diseases. As such, sleep appears to improve physiological pathways robustly.

In addition to physiological effects, there are many cognitive benefits of increased sleep, including improved memory, problem solving, and reaction speed.

Normal or acceptable range

The American Academy of Sleep Medicine recommends at least 7 hours of sleep per night for adults aged 18-60 years, with the National Sleep Foundation recommending supplementing this recommendation with 7-9 hours of sleep per night for adults aged 65 years and older.

Biostrap records users’ sleep each night, and from this data, we can gather average values of distinct populations.

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Interpreting Trends

Considering the broad health implications associated with sleep duration, tracking sleep duration over time is recommended so an individual may notice trends in their behavior. This metric can be seen as a health behavior, and thus influences passively obtained physiology metrics. However, sleep duration can be monitored to see if other lifestyle factors or stressors are decreasing time asleep, which may be hard to notice in some individuals without measurements. Including sleep duration into longitudinal metrics can either explain or rule out other physiological trends, and therefore is included in Biostrap biometrics, allowing users and remote monitors to have a broader view of individual health.