My first thought on this question was that perhaps the manufacturers of alarm clocks couldn't decide between the not-quite-long-enough 5-minute snooze and the potential for falling completely back asleep afforded by the ten minute snooze.
So, they compromised after many lively debates on the topic and now we all have an 8-minute snooze session. As a scientist, I wanted to determine the neurological basis for keeping a person on the fine line that separates sleep from wakefulness. It turns out, however, that the true basis for the 8 (to 9) minute snooze lies within the clock’s mechanics. Classic alarm clocks are built on a three bit counter that refreshes at the start of the ninth minute. The snooze button taps into this moment to reset itself. Newer digital clocks, however, allow for all different snooze settings. I have reviewed some basic sleep principles for you to consider in the case that you have the luxury of setting your own snooze duration (and actually want to get up).
That magical morning moment when sleep becomes wakefulness requires that many physiological systems line up. When we sleep, our brains cycle through five different stages of sleep that have been defined as stages 1-4 and rapid eye movement (REM) sleep. Stages 1 and 2 are lighter levels of sleep while 3 and 4 are deep sleep (also known as delta sleep). REM is the sleep period during which our brain is the most active, creating dreams. This may also be the most important part of sleep for learning and memory. We move in and out of REM sleep several times during the night and end up spending approximately 20% of our sleep time in REM sleep; when we are awoken during an REM sleep cycle, we often remember our dreams. As we approach morning, our sleep cycles are shorter and the time spent in stage 1, stage 2, and REM sleep increases.
When our alarm goes off in the morning, our body has been preparing for wakefulness by altering its temperature and hormonal milieu. Our brains move out of stage 1 or REM sleep to shut off our alarm. If we turn it off all the way, we may have a bout of sleep-induced amnesia that causes us to forget the brief moment of wakefulness. However, if we have a snooze button that keeps us from moving fully back into stage 1, we can slowly wake up and keep the new day in our consciousness. I am, however, unaware of any scientific publications that define a specific physiological or neurological event that occurs at 8 minutes after waking.
As one final note, it is recommended that adults get seven to nine hours of sleep a night and many factors including insomnia, sleep deprivation, napping patterns, and lifestyle- can alter normal sleep cycles and make it harder to get up in the morning and you may need to adjust your snooze schedule accordingly.
Figure can be accessed at: http://helpguide.org/life/sleeping.htm. September 29, 2008.