The Biology Behind Early Birds & Night Owls
When do you feel most productive? Do you prefer to get up at the crack of dawn to crack on with your to-do list or burn the midnight oil by working until the birds start singing? Us humans have productivity preferences not just based on the time of day but on our individual internal rhythm. Those who jump out of bed first thing in the morning are often referred to as ‘Larks’ (early birds) whereas the people who find it difficult to fall asleep before 2am are called ‘Owls’ (night owls). There are actual biological distinctions between these two categories and the impact of our ‘9-to-5’ lifestyle can be unfavourable for certain day-night routines. So whatever time it is where you are, I hope you are feeling wide awake to learn about your preferred sleep-wake cycle!
Tick Tock: Your Circadian Clock
Our day-to day routines are normally scheduled around our perception of ‘day’& ‘night’ and we categorise these two periods in various ways. Firstly, our daytime window comes from the rising and setting of the sun. The timing of the solar cycle when the sun is casting light on Earth is our ‘day’ whereas the rotation of our part of the planet away from the sun’s beams is ’night’. Another way we define our day and night is prescribed by our societal calendar. The majority of jobs, activities and engagements require people to be up and about during the day leaving the night for rest. The sun and society dictate your periods of wakefulness and slumber.
However, our third perception of daytime and nighttime comes from within us. We all have our own internal clock which generates a circadian rhythm; a reoccurring pattern running on an approximate 24 hour schedule, with a periods of rest and rouse. This ticking of this clock is controlled by a ‘pacemaker’ in the brain called the suprachiasmatic nucleus: a collection of neurons in the hypothalamus which are stimulated by the nerves from your eyes. The neurons in this region of the brain use stimuli like light to signal to the rest your body what time it is; causing actions which drive our feelings of alertness and sleepiness. This includes the release of chemicals like melatonin, which peaks during the night time, and cortisol, peaking as you wake, as well as altering body temperature. Our circadian rhythm repeats like clockwork to make sure you get your 40 winks once a day.
Shifts in the Cycle: Early Bird vs Night Owl
Although all our circadian rhythms run on a 24 hour schedule, people recognise their preference for staying up late versus getting up early. It is well-noted that different individuals experience their peaks and pits of the chemicals described above at different times during this period; with early birds experiencing a peak in melatonin hours sooner in the day than night owls. Population studies based on survey and hormone data suggest the split between the number of early birds vs night owls is about 50:50. An individual circadian rhythm can be altered with external queues like light and darkness; experienced when settling into a holiday after travelling multiple timezones (and desperately trying to reset on the way back home!).
However, even once you have adjusted to your new timezone, you will probably find that your preference for an early start or late dart remains the same. This is in part due to your genetic code. In your DNA, specific ‘clock genes’ have been identified which produce proteins involved in driving your circadian rhythm. For example, one of these proteins determines the a signalling event in the suprachiasmatic nucleus during the daytime and a mutation in this gene in human’s can cause a sleep disorder leading those affected to wake up extremely early. Therefore, being an early bird or a night owl is not necessarily a choice but an instruction dictated by your DNA, and trying to sway from your gene’s tailored alarm clock is a hard thing to battle!
Working 9 til 5: Impact of Mismatch
The impact your sleep-wake cycle preference has on your health has been experimentally tested and unfortunately for those late-night laddies, early birds appear to reap the most benefits. People whose circadian rhythm favours rising early in the a.m have been correlated with having better quality sleep and eating healthier, whereas the more nocturnal among us have been shown to have an increased incidence of sleep disorders and decreased physiological well-being. It is thought these disparate differences in health between the two sleep groups arises due to the ‘jet-lag’ night owls experience day-in day-out caused by the mismatch between their internal and societal clocks.
The underlying biology for why this mismatch in cycle could be negatively impacting night owls is coming to light. New research suggests a reason why early birds report having improved attention and cognitive state during the day than late-sleepers. Optimal cognitive performance and mental health are thought to be determined by the coordination of functional neuron networks within your brain, with the default mode network representing your brain’s state when not being commanded by external tasks. In individuals with a preferred late sleep onset, the activation of the default mode network, known to contribute towards attention and working memory, is significantly reduced compared to early birds during the timings of a ’normal working day’. This highlights one potential reason why the health of night owls differs from early birds – favouring a shift in our constrained work day to fit an individuals circadian rhythm in order to optimise personal performance.
There is a little bit of a reason behind why you like to get up early or stay up late! Whether you are an early bird or a night owl, your bed time and rise-and-shine effect so much more than just feeling tired. Your internal clock is determined by your genetics and environment, and ideally, you should be able to align your routine with your natural internal rhythm. However, the way we have built our working world could be detrimental to health of potentially over half of the population. Hopefully the recognition of the importance of proper sleep tailored to individual biological needs is on the horizon and will allow us all to embrace our inner bird or owl!
Julia (@julia.ravey.science) xoxo
For more brainy bits of info, check out my website and for more on the early-bird night-owl science, check out this review!