Just a doctor and her Body Clock: Shift works & Circadian Rhythms
Routine. What is it? Something monotonous, something boring?
Perhaps it is a bit mundane, the same thing over and over again!
You wake up at same time every day;
You have breakfast, lunch and dinner at your scheduled time;
You catch the same train to work each day;
You meditate or go the gym or read a book at the usual allocated time.
Routine. It’s a luxury a doctor cannot afford.
I yearn for my body just to be “know” what to do given where the sun is in the sky
I want a body clock which is functional, a body clock which can guide, dictate and encourage a lifestyle around it.
I want to be able to create healthy habits which I can follow like clockwork – like a swim session or a dance class on a Thursday evening.
My issue is, I have no idea if I will be awake or asleep on a Thursday evening. Some days I could be just waking up to go to a night shift. Other days I would be making my way home from a long 13-hour day shift, knackered and ready to collapse in bed. That regular dance class on a Thursday evening – it’s a myth.
A doctor’s brain and body can be in a perpetual state of jet lag and confusion. Since starting my rotation in the intensive care unit where there are almost exclusively 13 hour shifts and frequent switches between night and day shifts, my body rhythm has gone fully berserk. My life’s “normal” does not have a definition anymore.
I randomly wake-up sometimes at 2am starving, my stomach wants lunch – as it is lunch time by my night shift standard. But my brain battles and wants sleep – it shakes his head and goes, “Common Komal, 2 am is bedtime, not lunch time” but my stomach just wouldn’t have it.
Sleep is my biggest misery – it eludes me when I need it and overcomes me when I don’t. Every doctor I know has a uniquely personal relationship with sleep – their own way to cope with reversing night and day shift patterns. Some are miserable before starting nights, other are miserable trying to recover back to daylight hours. Some east a proper dinner before starting a night shift, others eat a light breakfast in the evening hours. Regardless, whatever system you have adapted, doing a 180-degree flip on your body system takes a toll on you.
Every time I need to adjust back to daylight hours, I am waking up with a heavy head, ready to go back to bed by mid-morning. Other days I am wide awake at 3am ready to conquer the world.
Morning Larks and Night Owls
Personally, I have always been a natural night owl. My natural sleep-wake cycle is probably 10am round to 2am for my waking hours. I am never a happy bunny waking up at 6 am in the morning, that’s halfway through the night and my brain never really gets to its full functioning capacity until 10am. For other people 6am to 10am is their prime time of the day, the time where they are most productive. I also felt there was something weird about me for having those hours. I possibly even blamed my Pakistani background for my sleep schedule- I am after all from Karachi, “The City of Lights” where the entire metropolitan is alight even at 4am, restaurants and dhabas (roadside food stalls) still open serving tea and karahi (fried meat dish in tomatoes and black pepper). But turns out us humans are all programmed differently, and all have a slightly different circadian rhythm (our “internal body clock) and it has an evolutionary benefit.
When tribesmen looked out for danger during the night, it was very helpful for some people to go to sleep at 8pm and wake up with sunrise -“the morning person” making approximately 40% of the population. Others are evening people; they sleep late and wake up late morning or even in the afternoon – these make up another 30% of the population. The remaining 30% are the “inbetweeners” whose sleep cycles fall in-between these “larks” and these “night owls”. Imagine if everyone went to bed at 10am and woke up at 6am – they would have 8 hours of no night patrol leaving the collective population vulnerable for longer. The slightly different body clock reduces this unmanned night watch time of the community from 8hours to about 4 hours, ensuring the longevity and survival of the whole society.
How does your body know when it is time to sleep?
The answer to this question is the same reason why you suffer from jet lag when you travel to a new time zone. How does a cup coffee combat this, and keep you awake?
There are two influencing factors which dictate when your mind and body wants to sleep. The first it your internal 24-hour clock which creates a cycling day and night pattern deep with the brain in an area behind your eyeballs called the “suprachiasmatic nucleus.” The signals from here communicates with the rest of the body to determine when you are sleepy and when you feel awake. It also governs regular you time preferences for meals, moods, emotions, your core body temperature, your metabolic rate, the release of hormones like “cortisol” or the stress hormone and how much urine you produce. This twenty-four hour rhythm is called the circardian rhythm, (“circa” meaning “around” and diam, meaning “day”). The second is the chemical messenger called “adenosine” which creates a sleep pressure.
In 1938, two scientists Nathaniel Kleitamnn from the University Chicago and his research assistant Bruce Richardson did an exciting but pretty daunting experiment. They packed themselves loads of food and water and headed off in the depth of Mammoth Cave to cut themselves away from sunlight. They fashioned themselves hospital beds with tall bed legs that were each stood in a. bucket of water to prevent the creepy crawly insects climbing up to join them up in bed- ingenious! They wanted to know that without the faithful guidance of the sun, would their sleep wake cycle and core body temperatures become completely erratic. They lasted 32 days in the cave and made some exceptional discoveries
The circadian rhythm – the “Melatonin cycle”
The first was that our internal rhythm is not set by the sun on a daily basis – it comes from within and does not go haphazard without the feedback from the sun. There was a predictable repeating pattern of wakefulness interspersed with 9 hours of sleep. The second finding was that our innate clock is actually slightly longer than 24 hours – we now know that the duration of human’s innate body clock is around 24 hours and 15 minutes. We used the sun as feedback and to fine-tune and rest the timings to wind us back to 24-hour rhythm now and again. It is just as well that the “suprachiasmatic nucleus” is located above the crossing of the nerve fibres which transfer information from the retina (optic nerve chiasm) so it can sample the amount of light falling on the eyes and finetune your circadian rhythm accordingly.
Your circadian rhythm is like a sine graph – reliably goes up and down with time. The suprachiasmatic achieves this by communicating with the rest of the body with a chemical messenger called melatonin – also called “the hormone of darkness”. It is raised at night, soon after sunset and sends a ripple through the rest of the organs, like a siren blaring “It’s night time, it’s night time, prepare to sleep!”. It doesn’t cause you to sleep in itself, but it gives a powerful instruction to your body to start the process of sleeping. Once sleep is in progress, melatonin concentration decreases and by dawn, melatonin release is shut off – the absence of melatonin signals to your body that it is time to wave good bye to the sleep process and get ready to wake up and start a new day!
The modern world is biased to towards the early birds. Offices and schools start early, and those who wake up late like me are often branded lazy, lack routine and structure. Sadly, it I not your personal choice to be a “morning person” or an evening “person” – it is hard-wired in your DNA and runs in families. My dad is your classic night owl and I get the same from him. So, when I have day shifts and am forced to wake up early, I really struggle. My brain is barely functional until the late morning or early afternoon. However, when it comes to sleeping early, I can’t – I am so alert; it is my prime time; it is when I function best and when I am most creative. I have tried time and it me again to switch the lights off and try and sleep early, but sleep doesn’t come. I have stopped trying too hard now. I just end up faffing around the house or lying-in bed reading a kindle or chatting to my family. This means I am sleeping at the time set by my body clock (“late”) and am forced to wake up at the crack of dawn, or even before that – my “sleep debt” build and builds and builds.
The Sleep Pressure – the Adenosine debt
This brings us to the second influencing factors is a chemical called adenosine which creates a “sleep pressure.” Adenosine is a chemical messenger which keeps track of the time elapsed since you last woke up. The longer you’ve been awake, the more that chemical accumulates in the brain which has the effect on putting a brake pedal on the wakefulness-promoting regions and enhances the sleep promoting regions. The combined effect of this is that of a stronger “sleep pressure” and consequently making you feel sleepier.
You can artificially dampen the adenosine signal with caffeine to keep you awake. Sound familiar? Caffeine latches on the part of the brain called “receptors” which is usually occupied by adenosine. Whilst adenosine stimulates the receptors to signal to the brain to make you feel sleepier, caffeine does not. Imagine your ears as little receptors, adenosine is the “earphone” – it fits in giving you a loud sound message whilst caffeine is like “ear plugs” – it fits in to block out the sound. By plugging off the receptors, caffeine essentially disarms adenosine from exerting its sleepy effects making you feel more alert.
It is important to bear in the mind, adenosine keeps being produced regardless of whether you drink caffeine or not. It just can’t make any useful effect whilst caffeine is part of your circulation. However once caffeine is broken down by the liver and the effect wears off, the lack of caffeine combined with all the extra adenosine which is circulating you slump – “the caffeine crash” and you would find it very difficult to stay awake.
So, what happens during night shifts or back-to-back shifts where sleep deprivation prevails?
The longer your stay awake the sleepier you should feel. But for anyone who does night shifts you know that is not always true. You get waves of tiredness followed by a funny wave of being paradoxically awake. This is because although your adenosine levels continue to rise since you last woke up, your circadian rhythm – the sleep-wake cycle determined by melatonin continues its regular rhythmic 24-hour clock. The pattern of melatonin release doesn’t alter when you don’t sleep on a night shift. So, although you get progressively sleepy through the night to 4/5am, you catch a second wind of alertness when your circadian rhythm is on its upwards trend of alertness as it usually would be in the morning. It is funny that you feel sleepier at 3am during nightshift compared to 10am post-night shift despite being awake for longer and having not slept all night. However, when the circadian rhythms alertness in the afternoon– “the downwards slope” of the sine curve from about late morning you feel even more sleepy.
And what about the sleep crash where you sleep for hours and hours after a stretch of difficult long shifts? This happens because adenosine rises and rises throughout your waking hours and the only way to get rid of it is by sleeping. When it comes to night shifts or back-to-back day shifts where you aren’t sleeping very well, you are producing more adenosine when you are awake compared to what you are getting rid of by sleeping. You need approximately 8 hours of sleep to evacuate all the adenosine that has built up during the day – when you get less than this, which many doctors frequently don’t, adenosine begins to accumulate, and concentrations remain high – like an outstanding debt on a loan. You then carry on this outstanding debt onto the next payment cycle and then next. Each time, you begin your morning with higher and higher concentrations of adenosine and your sleepiness debt become greater and greater. Its probably why you slump and sleep for an absolute age after a long set of sleep deprived shifts to get rid of the extra floating adenosine in your body.
Are you getting enough sleep?
Although once can’t do a formal sleep assessment you can ask some question – Can you fall asleep late morning straight after waking up? Are you functional without caffeine in the morning? Can you wake up without setting an alarm? Do you keep reading and re-reading the same sentence over and over again because it just didn’t sink in the first time?
If any of your answers are any different to this order of “No, Yes, Yes, No” you probably are not getting enough sleep. Routinely sleeping less than 6 hours are associated with lots o health detriments. It weakens the immune system, increases risk of certain cancers, increased risk of developing Alzheimer’s disease. It makes your blood sugar erratic, it increases your sisk of your coronates becoming blocked, increases risk of psychiatric disorder, makes you feel hungrier and more last but not the least “The shorter you sleep, the shorter your life span.”
So, my fellow shifts workers, keep yourself as close to normality as possible. Highlight and stick to important parts of your routine as much as possible (my oneis shower before bed regardless of what shift pattern I’m on). Don’t drink caffeine past midday if possible as its half-life is something ridiculously long like 5-7 hours. I personally try and keep my eating patterns as close to normal as possible on night shifts – I eat a big dinner in the evening before my night shift and breakfast at the end. I only snack for comfort during the night. And SLEEP! In all honesty, I don’t believe there is any excellent way to do shift work where you negate all the negative health consequences. Just be aware it is ok to not feel great during shift work, human bodies are simply not built for it. If it is particularly affecting your wellbing, talk to you supervisors to see if you can negotiate something sensible.