In 2008 the sleep profession eliminated the fifth stage of the sleep cycles. This wasn’t done because so many Americans were not getting the sleep they needed: the proper number of hours needed, nightly, is still the same. Instead, scientists found too many similarities between stages three and four sleep in the old five-cycle map and decided to combine them. But while scientists can adjust sleep cycles, and sleepers can firmness with an adjustable bed mattress, fully removing a cycle will reap consequences.

Some people wave a hand of dismissal at the talk of sleep cycles. But maybe if they understood the importance of those cycles on the body’s daytime function, they would take their nights more seriously. As of 2011, there are four acknowledged cycles of sleep. The first is a light drifting, easy to be wakened from, with rapid brain waves and subtle eye movements. Many people will experience muscle contractions in the first state leading to that sudden feeling of falling.

The second through fourth stages of sleep, in a healthy routine, dominate the night. In stage two the eyes stop moving and the brain fires only a few rapid waves. Third stage (a combination between the former third and fourth) is dominated by delta brain waves, a methodical brain pace. While in the third stage there are still some rapid brain waves, by the final stage, only delta waves continue. In this fourth stage, temporary muscle paralysis occurs, and many youth who struggle with bed-wetting are prone to do so in the deepest cycle.

REM sleep, while well known, is not considered a stage by most sleep experts. Though it is a feature of every sleeper’s nightly pattern, it can be disrupted (and some science has proven a link between its disruption and the interruption of chronic depression) without harmful affects to the sleeper. No other cycle can be stopped without consequence to sleepers.

In order to function healthfully, sleep cycles are important. Over a person’s life, their time in each cycle will shift, just as an adjustable bed mattress can be tilted or tipped, but their progression through the stages cannot be withheld by early waking, not without health consequences. Loss of stage three and four sleep leads to a profound weakening of the endocrine system resulting in compromised immunity and therefore, frequent sickness. Eight hours of good sleep, is truly a lifesaver.