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Falling Asleep and Circadian Rhythm

January 6, 2021


"The average person needs five to 20 minutes to fall asleep. We call this sleep latency. So five to 20 minutes is normal. So some people come to me and they complain, ""oh gosh, it takes so long to fall asleep."" And I don't think they like to be alone in the dark with their own thoughts and feelings, but 20 minutes is totally appropriate. The flip side may come to my office and the patient says, Oh, I can fall asleep before my head hits the pillow. Well, if that's true, they're not necessarily a good sleeper. That person is too tired and should have gone to bed half an hour ago. So if you really needed to wake up at six and you know that your, your work time depends on that awakening go to bed at 9:30 or 9:45. So you have your five to 20 minutes to fall asleep, and then hopefully you'll get your eight hours. It will be absolutely continuous because it's absolutely normal in that sleep cycle to have some awakenings. So again, people come to my office and they complain. Dr. Sahni, I wake up four or five times during the night, and I say, so what that's perfectly normal. Waking up is not the problem, it's staying awake for too long. So I just want you to know wake is part of your night, not just sleep, it's not black and white, just like the daytime, even though the longer awake, the more tired we get, it's a linear relationship, that part's true. But superimposed upon that, there's a circadian rhythm, a 24 hour cycle. It's actually 24.2 hours and women are slightly longer. In men, a little bit less long, but on top of the average, no longer I'm awake, the more tired I get. There's certain times of the day that are more alert. And we all know this between nine and 11:00 AM. It's a pretty alert time of day. So if I slept really badly last night, I'm still pretty good at 10 o'clock in the morning. On the other hand, I might've slept really well last night, but now it's Saturday afternoon and I'm relaxed. I'm the only one home and I'm in my bedroom and the cat is on the bed asleep and it's two, three o'clock in the afternoon. I might want to lie down and join the cat. I might not be tired, but between two and 4:00 PM is a sleepy time of day, not the best time for me to give a lecture, but a very common time to take a snooze, whether you need it or not. So if you wait as long enough, you become more awake because again, the day changes. And so does our need for sleep and our sense of alertness."