- Eleanor Roosevelt (Former First Lady of the United States – 1884 – 1962)
By understanding that your circadian rhythm is your friend, you can optimize your sleep each day. Circadian rhythms are your body's internal clock or sleep/wake cycle which repeats roughly every 24 hours. Ideally, wake up at the end of a sleep cycle not in the middle of one otherwise you may feel tired and sleepy all day.
In a previous blog post, Use Different CPAP and Bilevel Settings, it was mentioned that I use 3 ResMed VPAP Auto adjusting bilevel machines with different settings on each to optimize my sleep every day. The machine I use each day is dependent on the situation that I am facing each day. The situations could be eating and drinking late, a hard day at work or doing a lot of physical activity and a normal day.
The average sleep cycle length is as follows:
Usually with Machines 1 and 2, I will sleep for 5 cycles or between 6 hours 15 minutes (375 minutes) to 6 hours 55 minutes (415 minutes) before waking up.
Machine 3, Eat/ Drink late usually results in either 4 or 5 cycles or 6 hours (360 minutes) or 7.5 hours (450 minutes) before waking up.
Whichever machine is used, once I wake up, I will sleep/ doze until I reach 7 hours and 30 minutes to 8 hours. That is, I will go another sleep cycle if necessary, so I have consistency when I sleep and wake up. You can see with machine 3 that I may not wake for 7 hours 45 minutes (5 cycles x 93 minutes). Using Machine 1, sleeping 5 sleep cycles may be only 6 hours 15 minutes (5 x 75 minutes).
In addition, I found the extra time from waking up at the end of the last cycle up to 8 hours of sleep and rest gives me that bit extra of up to 10% of wakefulness during the day. I no longer have a late afternoon/ early evening “little tired” period and falling asleep. The extra sleep time keeps me going strong till bed time of 11.30pm to 12.00pm.
By working out what my body naturally requires, I have stopped using the alarm clock to wake up. Now I only use an alarm clock in emergencies as a backup when it is essential I get out of bed by a certain time.
These sleep cycles will vary for each person. You can read more about 90 minute sleep cycles and the splitting up of sleep into two sleep sessions.
I was on my feet nearly all day and did not arrive back home and go to sleep till 2.37am, Saturday morning some 23 hours later from when I first woke up. I was generally feeling great all day. Had a little tiredness in the afternoon but I kept going and was feeling fine.
Saturday morning, I used Machine 2 and woke 8 hours 23 mins later. This is 6 cycles x 83 mins or 503 minutes. As it was the end of the cycle I got out of bed. I had to go to a meeting and function and did not get to Bed that night or Sunday morning to 2.51am. Again, I felt pretty good all day.
As I had eaten late on Saturday night, I used Machine 3 and slept to 10.19am or 7 hours 28 mins later. This is 5 cycles x 90 mins or 448 minutes.
This is an example of how I use the circadian rhythm cycles to my advantage. It is essential that you work out your own personal cycle as they will differ for each person. So when you find yourself in a similar situation you can work out when it is optimal for you to wake up and get out of bed. The alarm clock is set as a backup only. From personal experience, should I wake up in the middle of a sleep cycle, I will be tired and sleepy for the rest of the day. By using cycles, you can be refreshed and energized all day even though you have not had your normal amount of sleep.
Interesting, using the plane example, after 3.0 hours when I needed to get up out of bed, I awoke automatically and did not need to use the alarm clock. It was as if my body knew I needed to get up!
If I was using Machine 1, normal day and 75 minute cycles instead of Machine 3, eat/ drink late and had 3.0 hours of sleep, you can see I would have woken up in the middle of a sleep cycle. 2 cycles x 75 mins = 150 mins or 2 hrs 30 mins. 3 cycles x 75 mins = 225 mins or 3 hours 45 minutes.
You will note that I have average cycle length for each machine and I do not have a precise circadian rhythm like other people such as 90 minute cycles. There are a few reasons.
1. Sometimes there is a crossover in what I am doing for a particular day. For example, I may have a Normal Day with a lot of walking and a very large lunch. Using Machine 1, the cycle length will normally be 80 minutes rather than 75 minutes as shown above. That is, the cycle length will move towards the cycle lengths of Machines 2 and 3. Read more at: Different Bilevel Settings Example.
2. Using different machines may cause the first day of switching to have a slightly different sleep cycle. By the next night and thereafter should I stay on the same machine, the sleep cycle stabilizes and the length of the cycles are the same.
Body iron level helps regulate our circadian rhythms and their link to metabolism. You can read more at this article.
In additon, Research is supporting that a brain's ability to clear a protein closely linked to Alzheimer's disease is tied to our circadian cycle.
Rensselaer Polytechnic Institute. "Clearance of protein linked to Alzheimer's controlled by circadian cycle: Ability of immune system to destroy Alzheimer's-related protein oscillates with daily circadian rhythm." ScienceDaily. 10 February 2022.