"There is a global experiment that gets performed on 1.6 billion people across 70 countries, twice a year - it's called Daylight Savings Time."
- Matthew Walker
This month, the US Senate declared they were 'protecting sunshine' by making Daylight Savings Time (DST) permanent.
While this may initially sound great - partly due to some clever wording - in reality, no sunlight is actually being 'protected' by this change, it is just being delayed.
Like an artificially imposed jet-lag, springing forward deprives us of an hour of sleep in order to grant us more light in the evenings.
While blissful in the summer months, permanent DST would see the already bleak winter plunged into an extra hour of darkness, with some places not seeing light until 9am! Imagine dragging yourself out of bed for work knowing you won't see the light for another 2 or 3 hours!
In practical terms, permanent DST would force millions of schoolchildren to walk to the bus stop in the pitch black, while their circadian rhythms are still switched to night-mode. Combine this with the fact that early school start times are already incompatible with teen biology and brain development, and you get a classroom full of sleep-deprived, cognitively-impaired and rightfully grumpy teens (you can read about teen sleep in a future post).
The decision to deprive society of morning light is also a mistake for mental health. Lack of exposure to morning light is already known to contribute to the maintenance and remission of depression. In contrast, early morning sunshine synchronises our circadian rhythms, benefits our health and boosts positive mood.
Interestingly, DST doesn't seem to benefit the economy either. In fact, the US already tried to impose DST in 1974 to save on energy costs - however, the plan failed and the bill was reversed almost quickly as it was imposed. Public opinion polls also show support for the idea dropped from around 70% to 30% just a few months after implementation - people were fed up going to work in the dark!
Due to the fact that clock changes occur across so many countries, researchers have been able to examine the negative effects of DST in a huge and diverse sample. Consequently, we know that this one hour of sleep deprivation can have serious effects on our health and wellbeing.
For example, in 2014, a study looked at the incidence of heart attacks across the population before and after clock changes. Shockingly, losing one hour of sleep in spring increased the risk of heart attacks by 24% the following week. In contrast, gaining an hour of sleep when the clocks fall back reduced the risk of heart attacks by 21%.
A similar pattern of findings can also be observed for rates of stroke, depression and road-traffic accidents.
These striking findings illustrate the bi-directional relationship between sleep duration and health, and demonstrate just how sensitive our circadian rhythms really are.
When it comes to sleep, consistency is key and while more research is needed, many sleep experts suggest implementing a form of 'Standard Time' whereby our sleep schedules are no longer disrupted by bi-annual clock changes.
Hopefully, as research progresses, conversations between the experts and those responsible for making government policy will lead to better decisions for public health.
Overall, whether we gain an hour or lose an hour, changing the clocks has been shown to have an impact on our sleep and circadian rhythms, which in turn has an impact on our health and wellbeing.
Sleep Tip: In the week leading up to the clock-change, try to bring your usual sleep and wake time forward by about 15 minutes each day. That way, when the change comes, the impact won't be as much of a shock to your circadian system. Eating your meals a bit earlier can also help to prepare for this shift.
References:
Blake, A., (2021). No more changing clocks - history says be careful what you wish for on daylight savings time. https://www.washingtonpost.com/politics/2021/03/15/no-more-changing-clocks-history-says-be-careful-what-you-wish-daylight-saving-time/
Hansen, B. T., Sønderskov, K. M., Hageman, I., Dinesen, P. T., & Østergaard, S. D. (2017). Daylight savings time transitions and the incidence rate of unipolar depressive episodes. Epidemiology, 28(3), 346-353.
Sandhu, A., Seth, M., & Gurm, H. S. (2014). Daylight savings time and myocardial infarction. Open Heart, 1(1).
Sipilä, J. O., Ruuskanen, J. O., Rautava, P., & Kytö, V. (2016). Changes in ischemic stroke occurrence following daylight saving time transitions. Sleep Medicine, 27, 20-24.
Rishi, M. A., Ahmed, O., Barrantes Perez, J. H., Berneking, M., Dombrowsky, J., Flynn-Evans, E. E., ... & Gurubhagavatula, I. (2020). Daylight saving time: an American Academy of Sleep Medicine position statement. Journal of clinical sleep medicine, 16(10), 1781-1784.
Robb, D., & Barnes, T. (2018). Accident rates and the impact of daylight saving time transitions. Accident Analysis & Prevention, 111, 193-201.
Walker, M. (2021). How daylight savings time affects our bodies, minds and world. https://www.ted.com/talks/matt_walker_how_daylight_saving_time_affects_our_bodies_minds_and_world?language=en
Zhang, H., Dahlén, T., Khan, A., Edgren, G., & Rzhetsky, A. (2020). Measurable health effects associated with the daylight saving time shift. PLoS computational biology, 16(6), e1007927.