Human sleep is a cycle which consists of waking stage, Non-REM Sleep and REM (Rapid Eye Movement) Sleep. In the waking stage, your body will prepare you to sleep. Your body will start to slow down, your muscles start to relax and your eye movements will slow down. After the waking stage, you will come to Non-REM Sleep which comprises of 4 stages and lasts from 90 – 120 minutes. In stage 1, the sleep is called drowsiness. The eyes are closed once you are in this stage. But if you are aroused from it, you might feel as if you have not slept. Stage 2 is the light sleep period. In this stage, the polysomnographic readings will show intermittent peaks and valleys, or positive and negative waves. These waves indicate spontaneous periods of muscle tone mixed with periods of muscle relaxation.
Muscle tone of this kind can be seen in other stages of sleep as a reaction to auditory stimuli. The heart rate slows, and body temperature decreases. At this point, the body prepares to enter to Stage 3 & stage 4, the deep sleep stages. Both stage 3 and stage 4 are deep sleep stage. However, Stage 4 is more intense than Stage 3. These stages are known as slow-wave, or delta, sleep. During slow-wave sleep, especially during Stage 4, the electromyogram records slow waves of high amplitude, indicating a pattern of deep sleep and rhythmic continuity. After Stage 4, you will come to REM sleep. The wave pattern in REM is quite similar to Stage 1 sleep. In this stage, you will experience intense dreaming.
After you fall asleep, the 5 stages Non-REM and REM stage will repeat cyclically throughout the night. The first cycle usually lasts for 90 – 110 minutes and each subsequent cycle will last longer. Getting to know the sleep stages of human beings has led to an invention called the bio-alarm clock which is designed to detect human being’s sleep stages and to wake sleepers at the perfect time. These bio-alarm clocks will detect brainwaves or body movements via some sensitive electrodes placed under the pillow case. The electrodes will trace what stage of sleep you are in and will wake you up during light sleep stage. Since a sleep cycle normally lasts from 90 -110 minutes, the bio-alarm clock will only have approximately a 30-minute margin of error.
There are a few types of bio-alarm clocks available such as Sleeptracker, SleepSmart and aXbo Sleep Phase Alarm Clock. Sleeptracker can be worn on your wrist like a watch. It will monitor signals from your body that indicate whether you are asleep or awake. SleepSmart is a headband with circuits that detect brainwaves during sleep, and the aXbo Sleep Phase Alarm Clock is a wristband that reads body movements.
Bio-alarm clocks are becoming very popular nowadays. Businessmen, travelers, students, etc. find it very useful and helpful. Having said that, there are also scientists who disagree with the use of these scientific products. Dr. Gregory Belenky, a sleep expert at Washington State University Spokane, has commented that light stage sleep isn’t the best time to be woken by an alarm. Dr. Gregory is of the opinion that light sleep stage is the hardest time to wake a person up unnaturally and he also has doubts on the functionality of this device. Waking up has become more sophisticated and complicated than when our mums used to holler from downstairs or when our sister/brother used to come and jump on our beds.
SleepTracker watch on Dr. Phil TV Show