Rockefeller University » More than just the winter blues – circadian rhythms are involved in diseases ranging from dementia to cancer

During this season, when the days are short and winter nights are long, it's easy to feel unwell. Those who suffer from Seasonal Affective Disorder, a type of depression that is closely tied to the circadian rhythms that govern our sleep cycles, know this all too well. But those same rhythms are themselves governed by your body's internal clock and can affect more than just your mood and sleep. Sophia Axelrod, Researcher genetics laboratory led by a Nobel Prize winner Michael D. YoungHere's how our circadian system works, its far-reaching effects, and how to keep it running smoothly.

What is the body clock and how does it establish our circadian rhythm?

This is actually a genetic program. Specialized photoreceptors in the back of our eyes have evolved to respond to a specific spectrum of sunlight, and the signal is transmitted to clock genes in the brain, which begin making proteins on a 24-hour cycle.

After all, nearly every cell in our body has a set of clock genes, all of which are synchronized to a master clock in the brain. This means we now have an orchestra of mobile clocks that are set by the light each morning. The impact is immeasurable. It is estimated that 50 to 80 percent of all genes in all cells are under circadian control. This means there are 24-hour fluctuations in all aspects of our physiology that impact health and disease.

When these clocks are disrupted, it not only causes sleep problems. They are also more susceptible to heart attacks, strokes, obesity, autoimmune diseases, increased infections, dementia, and even cancer. I was surprised at how far-reaching the health effects were. For example, we recently demonstrated that sleep, which is regulated in part by circadian rhythms, controls the permeability of the blood-brain barrier, which prevents all kinds of substances, including therapeutic drugs, from entering the brain. I did. This can affect not only health conditions but also our ability to treat them.

While you're referring to infectious diseases, we tend to get sicker when it gets colder outside, and we often blame it on the fact that we're all spending more time together indoors. How do changes in light exposure really affect you during the winter?

The immune system is a great example of how our bodies use circadian rhythms to create order between all of our different molecular functions. Many of the millions of biochemical processes that occur in the body each day cannot and should not occur at the same time. So circadian rhythms tell cells and organs in what order to do things. Our daily rhythms do not release T cells into the blood. One reason why we're more susceptible to infections when we get less light is because when our daily rhythms are disrupted, we may not have enough immune cells to fight.

However, this is not just a seasonal issue. Because we spend so much time indoors all year round, most of the light we get is weak artificial light. While modern civilization clearly has many advantages, one drawback is that many people do not receive the levels of sunlight necessary to properly stimulate this process. But thanks to high-intensity light therapy, it's a solvable problem.

Does using devices with artificial lights or bright screens at night further complicate the circadian landscape?

Not in itself. In fact, the difference in light exposure during bright days and dark nights tells your body what's happening. So, as long as you have lots of bright light in the morning, it doesn't matter what happens at night with indoor lights and screens. Daytime signals are so overwhelming that the body ignores everything else. But because many of us don't get sunlight in the morning and receive tons of light from screens at night, our bodies are in a state of circadian confusion.

How do you keep yourself in rhythm like a clock?

When you wake up in the morning, you want lots of light. And if you don't get enough sunlight, either because it's cloudy or you're working indoors with no windows, get a small light box. Keep it at home, keep it on your desk, and this is important, use it at least half the time. 1 hour. These really work!

If it gets dark very early, your body may become confused in the afternoon or evening and think, “Oh, maybe it's time to go to bed.'' If this is the case, you can use bright light again, including light from screens, to help you stay awake at night until you actually want to fall asleep. It's okay to take it until about 30 minutes before going to bed.

At that point, if you want to read or avoid tripping in the bedroom, a red light lamp will come in handy. Red light does not activate your body clock, so your body becomes sleepy and enters a relaxed state.

Controlling your light environment is an easy way to help your body do what it's supposed to do.

Do you have any other tips for avoiding circadian disruption?

Sleep hormones have circadian rhythms, so consistently shifting your bedtime and wake time reduces your body's ability to tire out at night. Maintaining your circadian rhythm means doing everything, especially related to sleep, at the same time every day. That means waking up at the exact same time and going to bed at the exact same time. Get morning light at the same time and eat at the same time.

That's difficult. During holiday breaks and weekends, we often want to sleep in, but some people need to make up for lost sleep. However, from a circadian rhythm perspective, keep things as tight as possible.