Integrating Circadian Synchrony at Night

4 Evening habits that support synchrony

Eat a light dinner, not too late ~ Getting to sleep quickly depends on your core body temperature being able to cool down starting about an hour before bedtime and continuing gradually through the night until about 2 to 3 hours before you wake up in the morning.  Eating a large dinner or eating within 1 to 2 hours before bedtime can disrupt your body's core cooling process and keep you from falling asleep quickly and soundly. 

Take in the twilight ~ Photographers know that both the morning and evening twilights are powerfully beautiful times of day. Even though the sun is below the horizon, the twilight sky is often brighter than most interior lighting for at least the hour before (dawn) and the hour after (dusk) the sun crosses the horizon. Several studies suggest that an intensification of blue light during twilights is an important synchronizing signal to our circadian timekeeper in the brain. If you tend to stay up too late, dawn twilight can help shift your wake up time earlier, and if you tend to wake up too early, dusk twilight can help you shift your wake up time later. 

Avoid bright lights 2 hours before bedtime ~ Exactly how our body goes to sleep is complicated and still a bit of a mystery. One key part of the sleep onset process begins when melatonin is secreted by the brain in response to darkness. If you are exposed to bright lights near your sleep time, especially blue-enhanced light like “full spectrum,” white compact fluorescent or white LED lights, melatonin secretion is suppressed and sleep is compromised. Using amber glasses, amber monitor filters or theatrical gels, yellow CFL bug lights, and just turning off unneeded lights in the few hours before bedtime can improve your sleep.

Wind-down before bed ~ In this time pressured world, many of us are continuously looking for ways to fit more into and get more done during our every waking minute. The problem with working and doing until we collapse, exhausted into bed, is our physiology works best when we transition into sleep rather than trying to turn off like a light switch. Cortisol, a key stress hormone, ideally reaches it’s lowest levels in the evening and should stay low through the early stages of sleep. Working during this evening wind-down time can keep your cortisol levels elevated, and elevated night time cortisol is associated with suppression of the most restorative phases of sleep, (early slow wave sleep) and impaired memory consolidation processes that are critical to learning (hippocampal long-term potentiation). Instead of working, use the hour or two before bed for activities don’t require a lot of light, are calming and a break from your livelihood. The ‘lost’ work time will be more than compensated by more restorative sleep and improved work performance the next day.

Dynamic Daily and Seasonal Cycles of Sunlight
The Survival Value of Predictive Adaptation
Circadian Synchrony and Optimal Physiological Function
New Approaches to Wellness and Treatment
Integrating Circadian Synchrony with Contemporary Life
Afternoon Tips for Circadian Synchrony
Integrating Circadian Synchrony at Night
American Society for Photobiology
CIrcadian Rhythm
Healthfinder Sleep Resources
International Dark Sky Association
Kavli Institute conference: Biological Switches and Clocks
National Sleep Foundation
Sleep Research Society