Written by Dan Murphy 28th April 2020.
Sleep and Circadian Rhythms
So, we’re in Lockdown. For a lot of people, including me, the hours and days have merged into one, which isn’t ideal. However, this bizarre time is perhaps the perfect time to take a deeper look into one of the most important parts of your day - your sleep.
With a large majority of the population off work, working from home or working different hours, you may find yourself naturally and consistently going to bed and waking up at very similar times each day with no need for your alarm. This could be you returning to your natural Circadian Rhythm.
Circadian Rhythms are your 24 hour internal body clock controlled by your brain. Specifically, it is the suprachiasmatic nucleus (SCN), found in the anterior hypothalamus - the part of your brain that controls hormones and the nervous system. The hypothalamus controls many of your behavioural and physiological rhythms including temperature regulation, hormonal release and gene expression. On top of this, your circadian rhythms are also synchronised by external factors such as light.
Your natural predisposition to the sleep-wake cycle is referred to as your Chronotype, and these can be further grouped:
Early Chronotype ECT (Morning Lark)
You’re up early and go to bed early, and function better earlier in the day.
Late Chronotype LCT (Night Owl)
You’re up late and go to bed late, functioning later in the day.
Intermediate Chronotype ICT (Bit of both)
“But how do I know what Chronotype I am?” You can find out your Chronotype by doing the Morning-Evening Questionnaire linked here. This can be used to assess your individual circadian rhythms and gauge which of these Chronotypes you are.
“Now I know I’m (X) Chronotype, what else does this mean?”
Well, your Chronotype and variance in circadian rhythm can have an effect on your performance. You may find you train better or perform better at a certain time of day, this is because over the day you’ll show variation in optimal brain and physical function, with a certain time being your ‘peak performance window’.
Early Chronotypes (ECT) will unsurprisingly be less sleepy in the morning. Mental performance for them is found to be at its best very soon after waking and physical performance peaks at 5/6 hours after waking for aerobic or endurance training, and 7 hours for strength.
If you’re a Late Chronotype (LCT), you’ll reach peak performance around 12 hours after waking up, this means your window for optimal performance over a day is much smaller compared to ECTs. LCTs reach peak strength levels at around 20:00.
Late Chronotypes are thought to make up 40% of the general population. Unfortunately, they’re most likely to be affected and have been battling constant circadian misalignment, likely for most of their life. This can be purely down to societal norms: that 9-5 work schedule, 8-4 school day, early morning training sessions. Theses all take place during the LCTs biological night (when they should be sleeping) which can have detrimental effects to their performance.
So, if you’re ever feeling slow in the morning its likely because as a LCT, your cognitive performance has been shown to be significantly impaired when performing simple and complex tasks during early morning.
Come the weekend, many LCTs will likely return to sleeping in and later nights. But this further adds to their chronic misalignment, repeating the sleepy cycle, resulting in them experiencing effects to that of people jet lagged or working night shifts, often coined “Social Jet Lag”.
"I'm a late Chronotype. How do I gain more energy in the morning and sleep better at night?"
Do not fear - things can change.
You can try to hit reset on your biological clock. An earlier phase shift of your sleep wake cycle by just 2 hours has a multitude of benefits. These have been shown to be an improvement in self-reported measures of mental health, reaction time and grip strength as well as shifting the timing of peak performance and improving performance during sub optimal times of day all while reducing daytime sleepiness.
Some strategies to help shift your biological clock towards a more socially beneficial window include:
Your circadian rhythm is very sensitive to light, and you can use this to your advantage. Exposure to bright light early in the morning will advance your circadian rhythm, causing melatonin onset to begin and finish earlier. This should mean feeling more awake in the morning, and sleepier at night. Melatonin is the hormone responsible for regulating your sleep wake cycle.
Timed exercise can result in a rhythmic change melatonin and your core temperature. Exercising earlier in the day can produce a phase shift to an earlier sleep wake cycle. The 06:00 crew might be on to something.
Like exercise, the timing of your meals can also have an effect on your sleep. A morning carbohydrate meal can advance your core body temperature, helping to wake up earlier.
Below is a simplified example of the schedule given to participants in order to phase advance in a study by one of the leading researchers in sleep, Dr Elise R. Facer-Childs. If you’re wanting to try and wake up earlier and shift towards a morning type person, I suggest you give some of these a try!
Wake up time
Try to wake up 2-3 hours before you usually would, and maximise outdoor light exposure during the morning. You can also try a Seasonal Affective Disorder alarm clock that wakes you up by filling your bedroom with bright light.
Try to keep sleep/wake times fixed within 15-30 minutes, both on weekdays and weekends.
Try to go to sleep 2-3 hours before your normal bedtime, and limit light exposure during the evenings as much as possible. This includes blue light from your phone screen - most phones now have a "night-time" screen setting, that automatically changes your screen to a more sleep-friendly colour hue in the evenings.
Keep a regular schedule for meals if possible, and limit heavy meals immediately prior to sleep. Avoid caffeine after 15:00, or earlier if you are especially sensitive.
Hopefully some of these tips will help you gain a more ordered sleeping pattern.
Remember that sleep is the best recovery tool we have - no amount of supplements can give us the benefits of consistent deep sleep.