If you’ve every experienced jet lag then you know first hand the effect changing time zones has on disrupting your body clock. Tiredness, lack of concentration and feeling hungry at odd hours are all symptoms. But have you ever stopped to think about the workings of this internal timekeeper and the effects of aging on our body clock?
I often judge the length of a flight by the number of movies you can comfortably watch. I say comfortably because you don’t want to be caught at the climax of a movie as you are coming in to land, and desperately trying to find out whodunnit as you are pulling up at the air bridge.
With this in mind I chose to watch a documentary at the tail end of a flight because its 59 minute length allowed me to finish it before the preparation for landing announcements kicked in. The BBC Horizon documentary – Body Clock: What Makes Us Tick was a fascinating choice, and I have since recommended it to people to watch.
What is our Body Clock?
Every cell in our body contains a mechanism for telling the time. Our body functions are tied to change in light and dark as the earth orbits the sun in a 24 hour cycle. This regular adaption is know as circadian rhythm, originating from the Latin words circa meaning “around” and dies meaning “day”.
The biological clocks in our cells are kept in sync by a master clock housed in a structure called the suprachiasmatic nucleus, or SCN. The SCN is located in the part of the brain called the hypothalamus, and receives direct input from the eyes.
So your master clock in your brain coordinates your various biological clocks in your cells, which in turn set your circadian rhythms.
These circadian rhythms, tied to the natural cycle of day and night, control the production of melatonin that makes us sleepy, our body temperature, hormone release, eating and digestion and other important bodily functions.
Image: NZ Geographic
Geeking Out on Cell Function
In 2017 the Nobel Prize in Physiology or Medicine was awarded to Jeffrey C. Hall, Michael Rosbash and Michael W. Young for their discoveries of molecular mechanisms controlling the circadian rhythm.
Here’s how it works:
Genes live in the nucleus of a cell and are made up of DNA, which contains the instructions for making proteins. DNA never leaves the nucleus of the cell; its molecular recipes are read out in the form of messenger RNA, which leaves the nucleus and enters the cytoplasm (the outer part of the cell), where proteins are made. Certain body clock genes give the instructions for PER (period) and TIM (timeless) proteins to accumulate in the cytoplasm until the concentration is high enough that they bind together. When they do, they form complexes that enter the nucleus and shut down the genes that made them. After a few hours enzymes degrade the complexes, the genes start up again, and the cycle begins anew.
One cycle takes approximately 24 hours.
A Lark, a Night Owl, or a Straight-Out Martian
Few people have biological clocks that are exactly 24 hours in length. In fact the average is 24 hours, 11 minutes.
If the cellular cycle of your body clock is less than 24 hours you have no trouble rising in the morning. This makes you a lark.
It’s hard to say what percentage of people are naturally larks. Since our society runs more closely to a lark’s schedule you would expect it to be quite high, but when you ask people what they would naturally prefer if they didn’t need to consider work, school or other commitments, the number drops substantially. It is thought that around 10% of people qualify as natural larks.
If your body clock runs longer than 24 hours, every cycle you are slipping later in the day. This makes you a night owl, along with about 20% of the population. There are even some people whose body clocks run 24 hours and 39 minutes and that makes them perfect Martians, exactly equal to the length of a day on Mars.
Since cellular function coded by your DNA determines your body clock, being a lark, night owl or Martian is genetic and was decided before you were born.
How Your Body Clock Resets
If the majority of us have a body clock that is longer than 24 hours how do we manage to keep to a 24 hour schedule? And how can we travel to the other side of the world and experience the effects of jet lag, yet manage to reset our body clocks to a new time zone?
This is where the master clock in our brain comes in. As mentioned earlier our master clock receives input from our eyes, and it is sunlight, specifically the blue rays, that tell our master clock to reset. This resets all the important cellular functions and aligns them to the day/night cycle.
The Body Clock and Disease
Up until recently that worked like, well … clockwork! However when the light bulb was invented, we were no longer tied to the natural cycle of day and night, and this has impacted our body clock. Add to that the blue light emitted by electronic devices, which when used at night are artificially telling our brain it is daytime, you have the recipe for disrupted sleep, and snowballing consequences.
Recent research shows that this disruption to our circadian rhythms is impacting our health, and may be accelerating aging, exposing us to age-related health risks. Irregular rhythms have been linked to various chronic health conditions, such as sleep disorders, obesity, diabetes, depression, bipolar disorder, and seasonal affective disorder.
There is mounting evidence that disrupted circadian rhythms are an early warning sign of developing neurodegenerative diseases, such as Alzheimer’s, Parkinson’s, and Huntington’s, and that the circadian clock is heavily implicated in metabolic diseases, chronic inflammation, and cancers.
My investigation into sound and vibration therapy revealed that diseased cells sang out of tune. I wonder if this could be because of their disrupted circadian rhythms?
How Aging Effects Our Body Clock
There are changes to our body clock that are simply correlated to age.
Firstly, there is a tendency in adults over 60 years old to become more of a morning person. Sleep also becomes more fragmented. The time taken to fall asleep is longer and awakenings during the night become more frequent.
The preference to rise earlier is also expressed in better cognitive performance in the morning. One study showed older adults performed recognition memory tasks equally as well as younger adults in the morning, but significantly worse when tested later in the afternoon.
Increased difficulty in adapting to ‘jet-lag’ type changes in day and night phases is another way aging effects our body clock. The difference was found to be more pronounced in phase advance (ie. traveling east, or going onto daylight saving), compared to phase delay (traveling west, or ‘falling back’ after summer time), which didn’t show as significant age-related impact. This may be caused by reduced responsiveness of the aged master clock to light.
The ability of our master clock to reset our body clock declines with age. This may be associated with the yellowing of the cornea in our eyes, so that less light is transmitted to the master SCN, which in turn outputs less rhythmic signals to our cellular clocks all around the body.
What We Can Do to Preserve our Body Clock
There are a number of things we can do to minimise how aging effects our body clock.
Ensure you are getting natural light in the morning to reset your body clock each day. This is also proving useful to aid recovery from some diseases, so much so that hospitals are looking to improve their lighting systems to mimic the day/night cycle.
Eating less appears to prevent tissue aging and, therefore, prevent stem cells from reprogramming their circadian activities. Also controlled, regular timing of food can have an effect on the cells involved in metabolising the nutrients and therefore reset their circadian rhythms bypassing the master clock.
Wearing glasses that block the blue light from devices can help prevent macular degeneration that may impair the eye’s ability to transmit light to the SCN to reset the master clock. Wearing these glasses in the evening may also provide less disturbance to sleep patterns.
Minimising stress helps to ensure your circadian rhythms are kept in sync. Stress releases free radicals that cause inflammation and disrupt the healthy rhythm of cells, so managing stress is an important part of reducing the effects of aging.
With the current state of international air travel I will at least not be suffering the effects of jet lag, but I may be missing out on other fascinating documentaries.
References
BBC Horizon: Body Clock. What Makes Us Tick?
National Institute of General Medical Sciences: Circadian Rhythms
Dave Hansford: Slaves to the Rhythm
The Nobel Prize: Press Release 2017-10-2
Linda Geddes: First physical evidence of why you’re an owl or a lark
Michael Young: The Tick-Tock of the Biological Clock
Adrienne Lafrance: Scientists Think Your Body Clock Was Set Before You Were Born
Suzanne Hood and Shimon Amir: The aging clock: circadian rhythms and later life
University of California, Irvine: Link between biological clock and aging revealed
Linda Geddes: Using light to reset the body clock can treat brain disorders
Top photo by Rodolfo Barrett on Unsplash
Heather Ogden-Handa
Good to meet you! I’m a marketer and writer interested in aging and longevity. I see lots of great information out there, so I’m keen to share topics that take my interest. Over time I hope the knowledge and community around this blog will have a positive impact on the healthy lifestyles of many individuals.