If you can’t sleep at night, but are sleepy during the day, one of the possible reason might be that your circadian rhythm may be out of sync with the day night cycle.
Of course if one can not sleep at night, one tends to be sleepy during the day. But many people are actually able to fall asleep during the day if they let themselves and are not constrained by needing to be at work. So that indicates that the body is able to fall asleeps, but not at the right time. This is a clue that the circadian rhythm is weak or out-of-sync.
The body’s circadian rhythm is like a natural internal clock. The “master clock” is the suprachiasmatic nucleus in the brain.
And your body’s hormones levels and other physiological processes are governed by this rhythm and the day-night cycle. For example, cortisol hormone levels should be high in the morning and low at night. Melatonin hormone level should be high at night and and low during the day. And many other hormones have day-night cycle like this.
If your circadian rhythm is off, your hormones will be off, and sleep does not come at the right time.
You say, but I know when it is daytime and when it is night time, I have the clock on the wall and on my phone that tells me. And I can see when it is day and night. So my circadian rhythm should know too. Unfortunately, that may not be the case. Your higher cognitive brain (the pre-frontal cortex) may know when it is day or night. But it is not the one controlling sleep or the circadian rhythm. It does not have the ability to control your autonomic processes. Just like your prefrontal cortex can not control your heartbeat or your digestion. If your pre-fontal cortex was able to control sleep, then you would not have any problem sleeping. You would just think, “Let’s sleep now” and bam you go to sleep. Just like as if you think, let’s raise my hand, and bam your hand is raised.
You may have conscious control over your hand, but not your sleep. What does have control over my sleep then? It is the pineal gland and its production of melatonin. The pineal gland is part of the old brain seated deep in the center of the brain. You have no conscious control over this gland or its production of melatonin. There are nerve pathways from the retina of your eye to the pineal gland. So the pineal gland get signals from the retina as to the amount of light that is in the environment.
Get bright natural sunlight exposure during the day and your pineal gland will know it is daytime. Keep your bedroom at night as dark as possible and your pineal gland will know it is night time. The stronger the intensity of the light during the day and the darker it is at night, the stronger the signal and the stronger your circadian rhythm will be. When your pineal gland gets good day-night signals, it will produce melatonin at the right time. Your body will be in sync with the day-night rotation of the Earth.
That is why some people say they can sleep better when camping outdoors aways from all the city lights. That is why some people can sleep better on the weekend after they’ve been outside all day, versus during weekday when they are inside an non-windowed office.
That is why you need to make your bedroom as dark as possible. To strengthen your circadian, get bright natural sunlight exposure during the morning. Spend at least a half hour (more the better) walking outdoors or eating your breakfast outdoors. Eat your lunch outdoors. Throughout the day, spend at least 5 minutes every hour being outside where you can see the blue sky. Even if it is an overcast day, still go outside. You may not perceive it to be so. But an overcast day outside is brighter than indoors, if you measure the intensity with a light lux meter.
If you are indoors, sit by the window during the day. While natural light without passing through a window is best (because glass blocks some UV light), window is still better than no window. At least you get greater light with window.
If work constraints prevent you from going outside, get a light box or use light box therapy.
Circadian rhythm occurs in most lifeforms including animals and plants of course, but also have been seen in fungi, cyanobacteria, and even in our own microbiome bacteria in our gut. Our gut bugs can not see light, but their cycle is govern by the feeding of the host. That is why eating only during daylight hours.
Ubiomeblog writes that our…
“The study also concludes that misalignments in the circadian cycle can result in metabolic imbalance and dysbiosis (a lack of bacterial balance), and that these may in turn have relevance in the diagnosis of modern human diseases.”
Jet lag mice have altered microbiome function. And when our microbiome is affected, sleep can be affected.
In the audiobook “The Stress Answer“, Dr. Frank Lawlis writes …
“Most sleep problems emerge from circadian rhythm disruption. That means that your brain is not sleeping in the natural patterns it was designed to do. You should be getting at least eight, and ideally nine hours of sleep (during the time the sun is not exposing you to light), especially if you’re undergoing stress of any kind.”
Dr. Dement’s book The Promise of Sleep writes …
“we defy our circadian rhythms and sleep indebtedness at our own peril. When we harmonize our lifestyle with our body’s master click, we maximize the quality of our life — physically, mentally, and emotionally.”