Ken Onishi is a doctoral candidate in integrative neuroscience. His research covers seasonal biology as it relates to immune function, the role of the immune system in clinical populations and the influence of gut microbiota on circadian rhythms. Ken is passionate about taking the small steps to make for a healthier lifestyle. Whether that means simply intermittent fasting to help with metabolic function, or freezing showers to help with inflammation, he believes in small, sustainable steps towards health.
Up until the invention of the light bulb in the late-1800s, humans organized most of our daily routines by the sun in the sky. Now, most of the world’s population lives in urban areas. In addition to adding one hour to clocks around your home after ‘springing forward’ did you know that the small shift in our social clock can have an adverse influence on health? The week following daylight saving time, we’re not only more tired after losing an hour of sleep, but there’s also a spike in car accidents and heart attacks! Remaining in synchrony with the world around you is vital to making your morning meeting and maintaining your overall health.
Circadian rhythms 101
*cue broad, scientific catchall phrase* All biological functions and behavior are oriented in time. Living organisms have a body clock that creates daily (circadian) rhythms. Circadian rhythms are ~24-hour cycles in physiological processes that drive changes in when we sleep and eat. Your mind is at its best when it’s aligned with its circadian rhythm . The body clock must match our 24-hour environment, where light from the sun is the main signal that adjusts the timing of our body clock.
Your body clock wants nothing more than to be kept steady and synchronized with sunrise. As sunrise and sunset change annually, our body clock uses light to gradually reset our circadian rhythms to match the new sunrise and sunset times. On average, this shift occurs at an hour per day. We’re all too familiar with the negative effects of this body-environment time mismatch when we travel across time zones. When you travel, you may feel the symptoms of jet lag (daytime fatigue, disturbed sleep, gastrointestinal problems or trouble concentrating) since your body clock is shifted from your ‘home’ time zone’s sun clock. For example, when you land in London from Chicago, your body clock is now 6 hours behind of the sun clock (local sunrise and sunset) since your body clock hasn’t had enough time to synchronize your circadian rhythms with the new time zone.
That’s it for our crash course in circadian rhythms. A lot of terminology, but here’s the gist of it: the circadian rhythms of our body clock want to remain synchronized with the sun clock. In addition to the adverse effects of jet lag by traveling across time zones, the social clock within a time zone can impact health.
Why is it important to stay in synchrony with the sun?
The earth rotates toward the east, and although individuals in the same time zone live according to the same clock time (coined social clock), our body clocks still want to remain in synchrony with the light signals from the sun (sun clock). Body clocks are earlier at the eastern edge of the time zone and become gradually as you head west. Studies have found that people who live further west within a time zone, the more health problems they experience. The best explanation for these findings is that the difference between our social clock – set by humans – and our body clock – set by the sun – increases toward the western edges of time zones. Thus, when 2 people wake up at 7:00 AM for work, the body clock of the person in the eastern edge may be set at 7:00 AM, but the person on the western edge may be set to 6:00 AM, and the difference between the body and sun clocks leads to health problems.
Daylight saving time (DST) was first implemented to save electricity by using less light in the evenings. DST disrupts the relationship between the social and sun clocks. During Standard Time, when our social clock says noon, it’s close to midday – the midpoint between sunrise and sunset. However, during DST Chicago’s social clock shows noon when it is only 11:00 AM by the sun clock (one hour before midday). People who have to get up at 6:00 AM by the sun clock in wintertime have to get up at 5:00 AM by the sun clock during DST, even though their social clock shows 6:00 AM. In addition to seeing DST as waking up for work one-time zone east, you could think of it as people’s body clocks being pushed further west while staying in their time zone. Since the body clock follows the sun clock, the mismatch between the body and sun clocks and the social clock can influence our health.
How does DST influence our health?
The first days after springing forward for DST in the spring, people experience shorter sleep duration, worse cognitive performance, and worse health. Heart attacks are higher during the week of DST compared to other weeks. Additionally, there are more traffic accidents the week of DST. These events suggest that shifting the social clock away from the sun clock can result in adverse health outcomes. The chronic effects of DST may last for months in some people since body clocks (that follow the sun clock) and social clocks remain set to different times.
While the phenomenology has been established, the mechanisms for the adverse effect DST on human health have not yet been revealed to scientists. One possible mechanism may be gleaned from the trillions of cells that make up the human body. When functioning normally, the clocks in your body are in synchrony with one another. Though, circadian disruption (in the form of jet lag or DST), clocks start to drift from each other and need time to resynchronize. It is possible that the disturbances in the circadian rhythms of these cells contribute to the adverse effects of circadian disruption on health.
During this time of circadian-disruption, you should be extra kind to your gut. That means taking a high quality probiotic, limited processed foods high in sugar and drinking lots of water. Why? Because when our gut is healthy, we experience increased energy and stronger immune responses overall–allowing us to overcome the health risks of DST in stride.
With all of that said, what does that mean to you? As it pertains to public policy, some developed countries have already eliminated DST in recent years with the help of public awareness. As it relates to your day-to-day life, I hope a greater awareness of the symphony of biological rhythms in and around us helps you adopt healthier, regular habits to reach your health goals.