Can devices detect your sleep cycle and wake you in a more refreshed state?

Question

There are a number of products on the market that claim to be "better alarm clocks" that allows you to feel more refreshed when you wake - even if you sleep a few minutes or tens of minutes less.

There are two claims:

1. that one feels more refreshed if one wakes during the REM phase of a sleep cycle, and

2. by monitoring movement as one sleeps, devices can determine the sleep cycle.

Examples of products that make such claims include:

• Sleep tracker
• Smart Alarmclock

SleepTracker’s SmartStart Technology monitors your sleep stages throughout the night and then uses that data to determine the exact moment when you should be awoken helping you feel refreshed and energetic. 1

Do these alarm clocks really make you feel more refreshed? Is such a thing feasible?

Answer 1

This article may be enlightening.

The most accurate method of measuring someone's sleep cycle is to use a bunch of electrodes attached to a person's head - I did this once. It's difficult to sleep this way because the gunk gets in your hair and restricts your movement in the night. However, measuring a person's movement during sleep - which is what all of these devices are doing is also very accurate.

This paper, claims to be able to accurately detect REM sleep from actigraphy and pulse monitoring.

Waking at the right cycle during sleep reduces sleep inertia - the feeling of grogginess. Here's a source explaining sleep inertia.

It is possible to fairly accurately monitor sleep cycles using activity, and waking up in the certain sleep cycles reduces grogginess, so their claims are plausible

Answer 2

The gold standard for measuring or monitoring sleep is Polysomnography (PSG for short).

However as Catherine says it's quite a cumbersome procedure. It monitors many vitals like EEG, EMG, Oronasal respiratory rhythms. Researchers have that's why tried a lot to analyse sleep using other easily available human vital signs. Accelerometry or Actigraphy (measuring body movement) gives valuable information on the depth of sleep.

That was the essence of all first generation research starting from 1960's until almost 2004. But now-a-days, few researchers have showed that it's possible to analyse sleep into 4 NREM (Non Rapid Eye Movement) and REM and a wake phase using the Heart Rate Variability (HRV).

There are numerous devices in the market that claim to analyse sleep. Most or all of them output various measures related to sleep efficiency. I'm currently doing a literature survey on the topic. In near future, we intend to devise our own algorithm that can do this in an effective way.

Btw, I'm a bio-medical algorithm developer.