The arrival of spring is the perfect time to speak of biological rhythms–an ideal "spring-board" you might say. In Canada, we are acutely aware of seasonal changes. As we await spring's warmth, some of us have been getting a little impatient. Although the weather is not yet spring-like, many other changes are already afoot.
Sap running in maple trees, male robins claiming their territories, groundhogs emerging from torpor: We are surrounded by signs of cycles that depend largely on environmental patterns of light and darkness. As we pass the equinox in the northern hemisphere, our daylight is now becoming longer than our darkness. These changes in light patterns lead to seasonal changes in behaviour. For example, birds respond to spring sunlight patterns with changes in their migration, mating behaviour and songs.
Just as the earth's orbit around the sun produces such seasonal rhythms, the daily rotation of the earth on its axis produces 24-hour cycles, known as circadian rhythms.
Our busy-ness with work and family in our electric, electronic age distances us from our own circadian nature. We can ignore this fact or we can embrace our circadian-ness. Failure to appreciate our circadian rhythms doesn't usually put us in peril, but it adds to our discomfort and perplexity upon arrival in new time zones, when working a night shift, when we have insomnia, and at the spring time-change.
The recent spring-forward of our clocks for daylight savings time forced us humans to notice our own intrinsic clockwork. Or, as I like to see it, it allowed us to observe our amazing circadian process at work, a process we often ignore. Some of us were grouchy and hard to rouse from sleep in the mornings immediately after the time change. This is because our circadian rhythm of sleep and wakefulness was no longer synchronized with the time on our cell phone.
At their core, circadian rhythms are controlled by genes, the so called "clock genes." Rhythmic clock gene expression allows light-dark patterns, via the eye's retina, to reach sites in the brain (the suprachiasmatic nucleus, which is the central circadian pacemaker and the pineal gland that regulates the release of the hormone melatonin) to synchronize the body's various circadian rhythms.
Just as these systems align the robin's territorial behaviour with spring, they also align his pattern of being active during daylight and sleeping during darkness and our own human 24-hour rhythms.
Perhaps our most fundamental circadian rhythm is that of our body temperature. Although it fluctuates by less than 1 Celsius degree in 24 hours, it does so in a reliable oscillation. For most of us, this means that our body temperature declines over the evening, reaching a trough about 5 am, then rises over the morning and peaks roughly 12 hours later in the early evening.
In concert with this temperature rhythm are several hormonal and behavioural rhythms. For example, cortisol (a hormone involved in stress responses, regulating metabolism and inflammation) has a pattern of release that roughly parallels the temperature cycle, as does our mental performance (e.g., on tasks involving memory, mathematics and reaction time).
Our sleep-wake rhythm is tied inversely to the temperature cycle. Perhaps you felt a bit chilled some late evening as your body temperature dropped and you became sleepier? By nature, we fall asleep as our body temperature drops and wake up as our body temperature rises in the morning. Thus, sleep itself has circadian rhythmicity.
So how can we appreciate these internal cycles that exist to synchronize ourselves with the external environment? Here are my suggestions:
· Wake up and get out of bed at the same time each day, 7 days a week. This will help your sleep and support the synchronization of your circadian rhythms. Soon, you'll be waking up with no alarm required. "Sleeping in" on week-ends is overrated: It allows your circadian sleep-wake system to lag, leading among other things to grumpiness on Monday morning.
· If you have trouble waking up at your desired time in the morning, expose yourself to natural or home lighting upon awakening so that this important "zeitgeber" (literally "time-giver") can help you align your sleep-wake rhythm with your schedule.
· In contrast to morning brightness, have relative dimness in the evening an hour prior to bed. That includes turning off the television and all those electronic gizmos. Exposure to bright light delays sleep.
· With jet lag and rotating shift work, the circadian system cannot adjust immediately. Honour this; we are not robots. Allow time for the transition and take care of your health. Research is examining ways to accelerate the adjustment of our circadian rhythms to the needs of our modern lives, including for travel and employment.
Adjusting to jet lag and shift work is a topic for another day. Right now, a robin is singing his heart out in the neighbour's pine and I'm heading to the sugar bush.
Dr. Judith R. Davidson is a clinical psychologist and sleep researcher. She works with the Kingston Family Health Team and Queen's University at Kingston. She is the author of Sink into Sleep: A Step-by-Step Workbook for Reversing Insomnia. You can follow her on Facebook and on Twitter at @JudithRDavidson