Our bodies’ inner clock is quite remarkable. It can work really well sometimes, while at other times, it gets completely thrown off. So what is the circadian rhythm, and how does it work?
What is it?
According to Wikipedia, a circadian rhythm lasts approximately 24 hours and persists even in the absence of variations in light and dark; can be reset through changing the environmental conditions one is exposed to; and the body adjusts temperature as part of the rhythm. Even certain bacteria display circadian rhythms, so this is not something that’s unique to humans.
Light and dark play an important role in the circadian rhythm. There’s a direct connection between specialized photosensitive receptors in the retinas of the eyes and the suprachiasmatic nucleus (SCN) in the brain. The SCN acts as a regulator of the circadian rhythm, triggering the pineal gland to release melatonin when it’s nearing time for sleep.
I was curious about how this might affect my blind blogging friends, so I did a bit more digging. The specialized ganglion cells that pick up light in the retina are functionally distinct from the photoreceptor cells used for vision, so a small proportion of people who are totally blind and the majority of people who have some degree of light perception maintain a normal light-dependent circadian rhythm.
In mice, mutations in the “clock gene” can lead to overeating and obesity, with increased risk for diabetes. In humans, shift work and other activities that disrupt the circadian rhythm can contribute to weight gain, heart problems, and inflammatory conditions. Excessive screen time on electronics is another factor that can disrupt the circadian rhythm. I work night shifts for one of my jobs, and I worry sometimes about the potential health effects. Still, I suspect sporadic shifts like I do are a lot less harmful than doing full-time nights, which would knock out the circadian rhythm entirely.
Life vs. circadian rhythm
I found the graphic above on Wikipedia. With it approaching winter where I live, it’s dark by 5pm, so the clock requires a bit of shifting. But even taking that into account, I’m very much abnormal. A typical day for me is to go to bed at 5:30pm (with the assistance of my regular bedtime meds, of course), and then sleep until 1 or 2am. I fully recognize how bizarre that is, and a lot of people are just getting to bed when I’m waking up. But if I was living in caveman times (or at least pre-fire caveman times), I’d be going to bed at 5:30 anyway because that’s when my melatonin would be peaking. Getting up when I do, my alertness is peaking when everyone else is asleep. My peak coordination time apparently happens when other people are spending some quality time on the toilet.
The last time I went off my medication, what I noticed the most was that I couldn’t sleep. I tried melatonin supplements and it did sweet bugger all. Taking oral supplements is probably a pretty poor substitute for your brain getting it right in the first place. I think my circadian rhythm is working the best it can, because I definitely get sleepy when it gets dark, but that’s not enough on its own to overcome depression’s desire to not let me sleep at all. That’s why I definitely need me some drugs.
Do you maintain a consistent circadian rhythm?
Sleep Better: The Little Book of Sleep is a mini-ebook that covers a range of strategies, both medical and non-medical, to help you get the best sleep you can. It’s available from the MH@H Download Centre.