It is that time of year when the annual tradition of commenting on quite how dark it is by 4pm is in full swing. While it makes for some convenient small talk, major biological changes occur every time we turn the clocks back.
The seemingly innocuous reversal of daylight savings time towards the end of October often has us rejoicing over an extra hour of sleep. However, this sudden adjustment of daylight directly interferes with our circadian rhythms. These rhythms are vital cycles embedded within our very biochemistry providing our cells a sense of time. Across the body are a series of internal clocks that control our circadian rhythms with the master clock located in the brain, known as the suprachiasmatic nucleus. This master clock relies on a series of cues in our environment, allowing coordination of vital bodily functions synchronised to the time of day, with light being the most crucial of these cues.
Adjusting the light levels so suddenly at the end of October can throw our circadian rhythms off balance. Our bodies’ clocks do not adjust quite as quickly as the clocks on our phone, so we are left experiencing a mild form of jet lag. A disrupted circadian rhythm can have far-reaching consequences for sleep quality, immune function, performance ability, and mental health.
Research indicates that even a single hour’s disruption can lead to increased fatigue, difficulty concentrating, and mood changes. Luckily this effect is seen more in the spring when the clocks go forward. But sleep data suggests we do not benefit from quite as much sleep as we think in the October shift—gaining only around 30 minutes of extra sleep. Regardless, this time alteration impacts our sleep schedule and accompanies an increased incidence of heart attacks and strokes. Impacting upon our blood pressure and cortisol levels when our circadian rhythms are thrown off balance, it becomes apparent why our cardiovascular system has elevated risk of dysfunction.
It is not just our heart that takes a toll, our mental state can also be affected. This is in part due to the regulatory role our circadian rhythms play in maintaining our concentration. A disruption to our sleep schedule can quickly interfere with our ability to remain productive and engaged, so it’s not just that you may be feeling that little more groggy in lectures in the days following the clocks changing.
As winter looms with the prospect of darker days to come, it is important that we continue to support our circadian rhythms as best we can to mitigate the risk to our biology. As with most parts of our biology, our internal clocks have an impressive ability to adjust to changes in our environment. We can support this by making sure we get sunlight as early as possible in the day and try to avoid excessive light in the evening. And while it may be tempting to take that cheeky nap following your 12pm lecture—it may do you more harm than good when it comes to keeping your circadian rhythms in check.