The body’s circadian rhythms are sensitive to many types of changes, but particularly to sunlight.
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Has the vacation disrupted your sleeping habits? Maybe you stayed up late to ring in the new year or changed time zones while traveling. Science journalist Lynne Peeples says the body’s circadian rhythms are sensitive to many types of changes, but particularly to sunlight.
In his new book, The inner clock: living in sync with our circadian rhythmsPeeples describes an experience in which she lived for 10 days in an underground bunker, without exposure to sunlight or clocks.
“I wanted to get a feel for my personal rhythm,” she explains. “We all tick a little differently, and so I wasn’t entirely clear on how my inner clock worked.”
Peeples says she quickly lost track of time and began to suffer from clumsiness and brain fog: “I think by the seventh or eighth day I was just letting go of everything and I really wasn’t not coordinated.”
Throughout the experiment, Peeples recorded his temperature, heart rate and glucose levels. She later worked with scientists to analyze the data she had collected over a 10-day period.
“Around the same time I was feeling really unbalanced, uncoordinated and a little crazy… that’s when the data showed that my heart rate and temperature rhythms were no longer coordinated , and also when I was becoming more and more uncoordinated with the sun,” she says.
Peeples says his time in the bunker illustrates the importance of daylight: “Our clocks and this coordination of our entire physiology really rely on these inputs of light and darkness to tell the body that it is day and night and to coordinate these activities. And when we don’t have daylight, When we don’t have these photons to help calibrate these clocks, then things go wrong and it affects our mental health and our physical health.”
Interview Highlights
The Inner Clock, by Lynne Peeples
via the riverside
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via the riverside
On the importance of circadian rhythms to our overall health.
We have billions of little “clocks” in our bodies. In reality, when you think about it, almost every cell in your body has a clock. And these clocks evolved to coordinate with each other and with the sun to help our bodies be prepared to do the right things at the right time. …We evolved to be more alert and awake and take advantage of daylight.
And “circa” in circadian means about or around. So our internal clocks have evolved to around 24 hours, but they are not accurate timekeepers. So we need regular calibration from the environment, from the Earth’s 24 hour cycle, to keep them in coordination with each other and with the sun. that they are ready to do the right things at the right time.
On the importance of daylight
Science suggests that light throughout the day is crucial, especially morning light. …It is clear that during the day, especially in the early hours, daylight will help us recalibrate our rhythms. And then throughout the day, the accumulation of that, getting those photons from the full spectrum offered by the sun, particularly those blue wavelengths of light that we get from the sun, will help align our rhythms and to make them more robust. . …
Then at night again, to maintain that contrast, to make the body understand that it was daytime and it’s nighttime where we’re supposed to relax to sleep, that’s when we need to ‘turn off the lights and not explode our ceiling lights in our homes, for example, or put our faces in front of screens. So it’s all about contrast.
Daylight Saving Time Disrupts Our Circadian Rhythms
When we move forward or backward, we inflict a dose of jet lag on ourselves, but we freeze the clock there. So when we move forward, we are essentially stealing an hour of morning light, which is when we really want light. And we keep that until the end of the day, when our body is really looking for darkness and it throws us out of alignment with the sun. Before we had world standard time locally, the sun was usually at its highest point at noon. And if we change that to daylight saving time, we lose that.
On everyone’s clocks that tick differently
We all tick a little differently. These internal clocks in our body that run at about 24 hours, for some of us that means they take a little longer than 24 hours, and for some they are faster and they take a little less than 24 hours to make their complete tour. , so to speak. This is why there are times during the day when we have a greater predilection for certain things. And if we think about sleep/wake, that’s where I think most of us experience these differences.
Some of us think that if we had a shorter circadian rhythm, we would be more likely to be early risers. It is easier for us to go to bed early in the evening and we might wake up early. And on the other end of the spectrum are extreme night owls, where they may be at their peak late and be awake and alert all night and then want to sleep late in the morning.
So it’s both about the speed at which our clocks tick and this alignment with light. Scientists are now trying to better understand this. But the way our bodies respond to light also affects how these clocks align with the 24-hour day. It’s not just early risers and night owls. There is a full spectrum that goes to extremes. Different genetics may program or predispose some people to function better during the night than during the day.
On how our clock changes as we age
Lynne Peeples is an MIT Knight Science Journalism Fellow. She is also a biostatistician and has conducted HIV clinical trials and environmental health studies. His writings appeared in The Guardian, American scientist And Nature.
John Cornicello/via Riverhead
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John Cornicello/via Riverhead
When we are first born, as our parents can attest, we don’t really have much rhythm. We kind of eat and sleep all day and night. And then, as we get older, younger children tend to wake up early, and that quickly changes when we reach adolescence. So at this point, early adolescence, our rhythms start to drift later, up to two or three hours. A child who was up, alert and ready to go at 6 a.m., now it’s maybe more like 9 a.m. And of course, that means it’s harder for these kids to fall asleep at night. And then as we get older, it evens out a little bit.
And then in our older years, on average, we tend to be maybe a little bit of an early riser. But… scientists are discovering that as we age, our circadian rhythms become blunted and weakened. So we don’t have such profound rises and falls in our rhythms, which manifests as a weaker sleep/wake cycle. So we might be more inclined to nap during the day. You know, you think about grandparents sitting in the chair and you fall asleep during the day and maybe you have trouble sleeping at night. This is still partly due to the fact that the circadian rhythm weakens as we age. But… we also understand how to potentially reinforce those rhythms, in part through things like getting that extra contrast of light and dark throughout the day.
On University of Pittsburgh research studying the correlation between certain mental health disorders and circadian rhythms
It may be that some medications used to treat mental health disorders, such as schizophrenia and depression, actually work by affecting the circadian clock. …This vicious spiral that happens with many mental health disorders where a person suffers from depression, for example, and stays indoors during the day. …Being indoors and missing the morning light then causes them to stay up later at night. And then it will encourage them to sleep the next day. And overall, it will weaken their rhythms. And if there is a connection between this and the disorder itself, it creates a snowball effect that some scientific research potentially suggests is an outcome.
On disruptions to our circadian rhythms and Alzheimer’s disease
The science is pretty clear: when we disrupt our rhythms, we disrupt our immune system and our ability to metabolize food at the right times of the day and all of those things. It’s no shock to scientists that this could have implications for how it could propel the development of cancer and heart disease, other cardiometabolic disorders, and in the long term, potentially dementia.. …
If we understand that, maybe it could help us find new treatments or help some people, as we get older, to access more of those signals, more of that circadian hygiene that helps their rhythms stay robust. And could this further delay and delay the onset of these diseases? Or if someone is suffering from this disease, could these stronger rhythms alleviate some symptoms and slow the progression of this disease? These are open questions, but there’s plenty of promising research that suggests there’s great potential here.
Sam Briger and Anna Bauman produced and edited this interview for broadcast. Bridget Bentz, Molly Seavy-Nesper and Carmel Wroth adapted it for the Web.