SATCHIDANANDA PANDA – Professor, Regulatory Biology Laboratory: So pathogens like this used to cause infectious diseases that killed humans for centuries. Until sanitation, vaccination and antibiotics took care of pathogens and gave us long, healthy lives.
But now, we spend nearly half of our life fighting with these kinds of chronic diseases, and for which there is no cure in sight. So today, I’ll share with you some really revolutionary ideas of how to prevent, manage and cure these diseases. And the idea is based on the concepts of circadian rhythm, our near-24-hour rhythms. To adapt to the 24-hour light-dark cycle, or day-night cycle, on our planet, almost every plant and animal has circadian rhythms that are controlled by what we call circadian clocks. These are actually encoded in our DNA.
And this is so fundamental to life forms on our planet that if we move any animal or human from this planet to another planet that has identical conditions as the planet Earth but has a day-night cycle other than 24 hours, then we cannot easily survive. In recognition of this fundamental property of circadian clocks and health, this year’s Nobel Prize was actually awarded to three scientific leaders in this field. And I’m really honored that all three of them have directly inspired and influenced my research.
So how do we know that these clocks are in-built? For example, if you lock me inside an apartment with no clue about outside time, then my circadian clock will make me go to sleep around 10:00 at night. I’ll go into deep sleep around 2:00, and anticipating waking up, my body will warm up around 4:00 in the morning.
As soon as I wake up and open my eyes, my sleep hormone melatonin will plummet, and my stress hormone cortisol level will rise. My peak performance time for brain will be around noon. And my peak athletic performance will happen around late afternoon. As evening rolls in, the circadian clock will crank up melatonin to make me go to sleep again, and my body will cool down to support my sleep. So this will continue every 24 hours, even if I’m locked inside an apartment.
And these rhythms happen because almost every single gene in our genome turns on and off at different times of the day. Every single hormone and brain chemical also rises and falls at different times of the day. So to have these rhythms is actually to have health. And when these rhythms break down, when we stay awake late into the night finishing an assignment or taking care of a loved one, then we feel horrible the next day. And if we continue abusing our clock for weeks or months, then all these chronic diseases can happen.
So it’s very important, then, to know how are these clocks organized so that we can nurture them much better. So as you can imagine, just like in our brain we have a clock that makes us go to sleep and wake up every day, the same brain clock sends chemical signals to the rest of the body.
But what is really surprising is that almost every organ in our body, and even every single cell in our body has its own clock. What does that mean? It means that just like your brain clock makes us more efficient at solving complex problems in the middle of the day, and also the brain needs to sleep at night, every organ has its own peak performance time at certain times of the day. And every organ needs to sleep, or rest and rejuvenate, at another time.
So all these clocks work together to give us daily rhythms in sleep, metabolism, mood and even gut microbiome. But how are these clocks connected to the outside world? In fact, every morning as we wake up and open our eyes, bright light goes through our eyes and resets or synchronizes this clock, so that when daylight savings time changes, or when we move from one time zone to another time zone, light synchronizes all of our clocks to the new season or the new time zone. But the property of light that resets our clock is very different.
Almost 15 years ago, we discovered a new blue-light-sensing protein called melanopsin. It’s present only in 5,000 squiggly neurons in our eye. And these light-sensing neurons are literally hard wired to our brain clock, to the master circadian clock. But they have a very interesting property. They’re less sensitive to light, and especially to orange colored light. So that means, in the evening, as we move around and find our way under candle light or dim orange light, the melanopsin is not activated. It sends a signal to the brain as if it’s dark outside so that the brain clock makes a lot of melatonin and we get a good night’s sleep.
And in the daytime as we wake up, go outside for at least an hour or so. The daylight is very rich in blue light. It fully activates melanopsin. That synchronizes the brain clock nicely with the day. It reduces sleepiness and depression, and increases alertness.
But the problem is, we spend more than 90 percent of our time indoors. And at nighttime, bright screens and bright light activates melanopsin; it sends a confusing signal to the brain, and the brain thinks it’s not night yet, so it produces less melatonin, and we sleep poorly.
The next day when we wake up, as we spend most of our time indoors, this indoor light is not rich in blue light, so it again sends another confusing signal to the brain, and the brain thinks it’s not day yet. So all the chemicals that should boost our mood are actually not produced enough. So we kind of go back and forth between insomnia and fogginess, and if it continues for weeks or months, then a lot of diseases can happen.
And what is interesting is, this is particularly important for children because their brain is still developing. And when children go through early childhood circadian disruption, they are more prone to diseases like ADHD and autism. So this new simple idea, that we need more bright blue light during the daytime and less light, or darkness, at nighttime, is starting a new lighting revolution. And you are just getting a glimpse of this new light revolution when your smart screen and computer screen dim down and turn orange at nighttime. But there is more to it.
Just think about it: Circadian lighting at daycare and schools will promote healthy brain development and promote learning. Circadian lighting at home, factories, offices, will promote alertness and improve productivity. Circadian lighting at hospitals or retirement homes will promote health and accelerate healing. And in fact, right now, there is new circadian lighting in our International Space Station to promote productivity of our astronauts and make them have better nights’ sleep. So light is not the only factor that affects our clock.