Your Circadian Rhythm
As we continue the conversation of sleep, the words circadian rhythm come up, but what actually is a circadian rhythm and how does it pertain to sleep.
The word circadian comes from the Latin phrase circa diem which means around the day. A circadian pattern means a pattern that repeats on a 24 hour schedule. This happens to many different systems of the body from sleep to appetite, alertness, body temperature and even physical performance. These patterns can be influenced by many different things from what foods we eat and when we eat them to the light in our environment. The most common or talked about circadian rhythm is our sleep wake cycle.
Our internal clock is run by a little region of the brain known as the suprachiasmatic nucleus (SCN) which helps anchor our circadian patterns. The suprachiasmatic nucleus is highly sensitive to light which links our internal biology to our 24 hour world. This is why many individuals have advocated getting morning sunlight within 10 minutes of waking up. This light signals to our brains that day has come and it is time to turn up alertness. It is the same reason we should start dimming or turning down lights and screens at night, sending the same signal to our brains that the day has ended and it is time to start generating sleep.
As we start talking about generating sleep, we see multiple body systems starting to collide. Our peak core temperature is usually around 3-4pm and we typically see it start to dip into the evening. This is vital because for our body to generate sleep, we need our core temperature to drop around 3 degrees. On the hormone side, our morning wake up is tightly correlated with a cortisol pulse that drives us up and into action for the day. As we progress into the evening, we see a release of the hormone melatonin which is responsible for generating sleep (not keeping us asleep). This is all an extreme simplification of a very in depth area of scientific literature but the outcome is the same. It takes multiple body systems to create the cycle we experience as our sleep and wakefulness cycle and disruption of any one of those systems can create disruptions in some of the others.
So, in actionable advice what does this mean? We want to keep our sleeping areas cool, allowing our core temperatures to drop. In the same line of thinking, we don’t want to work out close to bedtime, as the exercise induced core temperature elevation will make falling asleep difficult. We also want to bias showers in the evening on the warmer side. Cold showers can produce a dopamine response (not ideal for sleep) as well as vasoconstriction (smaller blood vessels) which makes it harder for our body to release heat and fall asleep. We also want to view sunlight within the first 10 minutes of waking up as well as in the evening, within a half hour of sunset. This sunlight helps set that internal clock and will help our brains more easily fall asleep at the same time every evening.
If you want to know more about circadian rhythms, look into the work of Dr. Satchin Panada of the Salk Institute, he is one of the world experts in circadian biology.
