It is amazing how many people struggle to sleep due to the simple fact that they are trying to sleep at the wrong time. In order to better understand when you should be sleeping, it might be best to start by considering the two major reasons we sleep at all.
There is admittedly much that we don't know about sleep. Our current understanding nevertheless identifies two processes that contribute to our ability to sleep: homeostatic sleep drive and circadian rhythm. The first concept is rather simple: the desire for sleep builds the longer that we stay awake. No one will argue with this; it's easy to test. The science behind it relates to the gradual accumulation of a chemical within the brain, or neurotransmitter, called adenosine. It makes us feel sleepy. And, incidentally, blocking it is what makes caffeine effective as an alerting stimulant.
The other major player in the timing of sleep is our circadian rhythm. This is the pattern of internal processes that are synchronized to the natural day-night cycles. This directs key functions of our body and associated behaviors, including: body temperature, blood pressure, hormone levels, hunger, and sleep. It strongly dictates when we feel tired and when we are most awake.
As a brief aside, each and every cell of our body has "clock genes" that direct the activity of the cell. Even our fat cells follow a circadian rhythm! This helps the body to coordinate its activities. There is a part of the brain that is responsive to light called the suprachiasmatic nucleus (SCN). The SCN is the central pacemaker of the body, coordinating all the peripheral clocks with carefully timed hormonal changes. Therefore, sunlight (especially morning light) seen through the eyes and relayed to the SCN has a powerful effect on our circadian patterns, especially when we sleep.
With the circadian patterns of sleep, there is also clear variability between people in the timing of the longest sleep period. This sleep phase may be delayed in people who identify as night owls or advanced in morning larks. Night owls often feel most productive into the late evening and may not go to bed until 2 AM or later. This delayed sleep phase syndrome is especially common among teenagers. Conversely, elderly people are more likely to have an advanced sleep phase and go to bed and rise earlier. This has important implications on the appropriate timing of attempted sleep.
If you are a night owl and your body's natural tendency is to go to sleep at 2 AM, what do you think will happen if you try to go to bed at 11 PM? It should be no surprise that you would complain incessantly of difficulty falling asleep (insomnia). It might take 2 or 3 hours before you fall asleep; coincidentally, right about the time that your body is ready for you to be sleeping. Imagine what would happen if you forced someone with a "normal" sleep phase to go to bed early. Instead of hitting the hay at 10 PM, this person is forced to go to bed at 7 PM. No one would be surprised if they complained of trouble falling asleep. When we attempt to sleep is key to our ability to sleep.
Many people are aware of their natural tendency, whether they prefer to go to bed early or stay up late. It may be clear throughout life, but it can also change subtly. For those who find themselves needing to sleep at more standard times, there are ways to harness the power of the SCN to fall asleep easier and wake feeling refreshed, no matter what time it is. If you have trouble falling asleep, take an honest look at your sleep patterns and consider whether you are trying to sleep at the right time for you.
Check out the entire series, "How to Sleep Better in 30 Days."
- What Are Circadian Rhythm Sleep Disorders?
- Delayed Sleep Phase Syndrome in Teenagers
- How Divided Sleep Periods Affect You
- What Are Clock Genes?
- Reasons Why You Can't Sleep