Why do some people wake up energized despite a lack of sleep and others tired despite a lot of sleep?
When we reflect on sleep, we notice that many people sleep only a few hours yet wake up feeling refreshed and energized. On the other hand, some individuals sleep for long hours but still wake up feeling exhausted and sluggish. So, what is the reason behind this intriguing paradox?
Sleep is one of the most essential activities in our lives and is crucial for both our physical and mental health. During sleep, the body works to repair tissues, rebuild muscles, and strengthen the immune system.
Moreover, the brain processes the information received throughout the day and stores it in long term memory. Sleep also improves mood, reduces stress and anxiety, and regulates the body's hormones. For these reasons, sleep is indispensable to our well being.
According to the World Health Organization and leading medical institutions worldwide, the average person needs 7 to 9 hours of sleep each night.
However, in reality, sleep duration varies from person to person. Many individuals sleep for less than 7 hours yet wake up feeling refreshed, while others sleep for longer but still feel as though they haven't had enough rest.
The recommended sleep duration is merely an average estimate, as several factors can influence an individual's actual sleep needs. For example:
Some people suffer from "Short Sleep Syndrome", a condition in which they naturally sleep only five hours per night without experiencing any negative effects. This is not a temporary condition caused by stress, such as during exam periods, but rather their normal sleep pattern.
Despite getting fewer hours of sleep, these individuals wake up feeling fully energized. What’s even more fascinating is that they do not suffer from any health complications due to their limited sleep duration it is simply enough to meet their body’s needs.
Researchers have yet to identify a definitive cause for this phenomenon, but they suspect it is linked to genetic variations, making this syndrome hereditary.
On the other hand, some individuals experience "Long Sleep Syndrome." These people require 10 to 12 hours of sleep to wake up feeling fully energized. If they sleep for less than this duration, they often feel fatigued and exhausted throughout the day.
However, modern lifestyles including work and study schedules often prevent them from getting the sleep they need. As a result, they frequently experience sluggishness and drowsiness during the day. On weekends or holidays, they may sleep for up to 15 hours to compensate for the sleep debt accumulated throughout the week.
This syndrome affects only 2% of the population. To diagnose someone with Long Sleep Syndrome, doctors must monitor their sleep patterns over an extended period. A proper diagnosis requires careful evaluation to determine whether the individual genuinely suffers from this condition or if their prolonged sleep is influenced by other factors.
Oversleeping, on the other hand, is a completely different issue. People who sleep excessively without their bodies actually needing it often wake up feeling sluggish and experience headaches. Over time, this habit can even increase the risk of depression.
Sleeping for too long disrupts the body's natural sleep cycle and affects the secretion of hormones that regulate sleep and wakefulness. As a result, even if a person sleeps for 20 hours, they may still wake up feeling exhausted and unrefreshed.
Another important point concerns individuals who sleep the recommended 8 to 9 hours without suffering from any of the previously mentioned sleep syndromes. Despite this, they sometimes wake up feeling fully refreshed, while at other times, they feel the opposite.
Dr. Eric Zhou, a sleep medicine professor at Harvard University, explains that most people focus on the number of hours they sleep, but they often overlook the environmental conditions that impact their sleep. These factors play a crucial role in determining energy levels and mood upon waking up.
For example, sleeping on an uncomfortable pillow, feeling too hot , or being exposed to surrounding noises can all negatively impact sleep quality.
Another key factor affecting sleep quality is whether a person enters deep sleep. Sleep is not a single phase but rather a repetitive cycle of stages. One of the most important phases is Non-Rapid Eye Movement (NREM) sleep, which is divided into three sub-stages and accounts for 80% of total sleep.
Following NREM comes the Rapid Eye Movement (REM) sleep stage, which plays a crucial role in cognitive functions and emotional regulation. If this sleep cycle is disrupted or incomplete, a person will wake up feeling fatigued and exhausted, even if they have gone through the previous three stages.
However, when all sleep cycles are fully completed without interruption, the person wakes up feeling refreshed and energized.
In conclusion, age is one of the most significant factors influencing the amount of sleep a person needs. Sleep requirements vary by age group as follows:
- Infants: 16 hours per day
- Children (ages 6–9): 12 hours
- Teenagers: 10 hours
- Adults: 7–9 hours
As a person ages, their total sleep duration naturally decreases. This is because the body’s circadian rhythm slows down, and the production of sleep-regulating hormones declines over time. This explains why elderly individuals tend to sleep fewer hours compared to younger adults.