Last blog, we discussed sleep apnea, which can have dramatic affects on sleep quality. In this post, I discuss circadian rhythm. Diagnostically, the field of sleep medicine has made huge advances. Less than a decade ago, if you wanted to understand your sleep patterns, it required an overnight stay at the hospital for polysomnography. Now, you can monitor your sleep with a high degree of detail through rings, watches, bedside devices, and more. These devices tells us the proportion of time a person spends in light, deep, or REM sleep. REM is important for memory consolidation and processing. Deep sleep is when growth hormone is released and repair happens.
Circadian rhythms are set in response to cues from our natural environment. Until very, very recently, our ancestors rose with the dawn and fell asleep soon after dark. There simply weren’t other options! The affect of artificial blue light from devices and screens has been well researched. Melatonin is produced in the pineal gland and is regulated by light-dark cycles perceived by photoreceptors in the retina. Melatonin makes us feel sleepy and keeps us in deep sleep. It is also a powerful antioxidant that plays a role in clearing toxic metabolites out of the brain through the glymphatic system.
Taking melatonin can be part of resetting circadian rhythm, but it isn’t the only strategy. We like sustained release melatonin supplements in fairly small doses – 1-3mg. Research studies have show that achieving deep sleep with melatonin in not dose dependent (at least not in a systematic way). Studies have also shown that regular melatonin use does not block natural production[i]. Ideally, melatonin in taken 2 hours before your desired sleep time, in combination with the practices below.
Resetting internal circadian rhythms starts with increasing (or mimicking) exposure to natural light cues. Melatonin is maximally released in the dark. Studies have show that light exposure between 12am-4am (the normal hours of melatonin production) will inhibit production for the rest of that sleep cycle. (Tip: put your devices in another room so those errant middle of the night disturbances from insomniac friends don’t ruin your sleep!)
Of course, following the circadian rhythm, darkness at night is followed by bright light exposure in the morning. Exposure to bright (10,000 lux) light in the morning triggers a phase shift in melatonin production, meaning it will begin to release earlier that evening. If you have a bad night’s sleep, one of the best things you can do is to take a morning walk in the bright sunlight for 30 minutes. If that doesn’t work in your schedule, consider a full-spectrum light box that emits at least 10,000 lux. I recall when I lived in Seattle and struggled against seasonal affective disorder myself. I had an elaborate system of self-care that included a full-spectrum light on a “Dawn simulator” timer that could be programmed to gradually brighten over 30 minutes for a gentle, full light awakening. It made a huge difference (at least until I walked into the pitch-dark hallway and remembered reality!) We sometimes forget to talk about light boxes as part of sleep disorders here in sunny San Diego but for many people who work indoors, insufficient exposure to high lux full-spectrum light is an easy problem to fix.
[i] Anderson-Ross, K. Sleep, the emerging science and its clinical applications. NDNR Mar 2018