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The Importance of Circadian Rhythms for Longevity

July 27, 2022

Throughout the past decade, studies have started to uncover the subtle relationship between circadian rhythms and aging. Various lifestyle practices can reset your circadian clock to promote health and longevity1.

That’s all very interesting, but what even is a circadian rhythm? And what makes it so powerful?

What Are Circadian Rhythms?

The circadian system is the conductor of your body’s orchestra. Headquartered in the hypothalamus, a small region in the brain, circadian rhythms regulate and synchronize our 24-hour cycle of biological processes. These rhythms are closely tied to your sleep patterns, appetite, body temperature, etc2.

Circadian rhythms are mainly internal, but they also respond to light. A structure in the hypothalamus, called the suprachiasmatic nucleus (SCN), has an intense reaction to light. Nearly 80% of SCN neurons experience increased activity with light exposure. Essentially, light informs our SCN that it’s daytime so it can adjust our rhythms accordingly3.

How do Circadian Rhythms Influence Our Body?

During different phases of the circadian cycle, the hypothalamus sends signals and secretes hormones to prompt different reactions in the body. This cycle consistently influences hormone levels, body temperature, metabolic regulation, etc2.

Hormone levels

Hormones are critical to sleep times. In the evening, the hypothalamus stimulates melatonin, also known as the sleep hormone, to make you drowsy. 4 Cortisol, on the other hand, increases alertness. In the morning, the hypothalamus activates cortisol production and it gradually declines throughout the day5.

Environmental factors, such as light inhibits melatonin production to keep you awake, making sleep a distant dream.

Body temperature

The hypothalamus is responsible for maintaining a specific temperature in the body. When it’s hot outside, the hypothalamus sends activating signals to your sweat glands to cool you down. When it’s super chilly, it stimulates your muscles making you shiver, so the movement can keep you warm6.

Body temperature also fluctuates during our daily cycle. Melatonin actively cools us down to encourage sleep, which is why our body temperature is lowest at night7.

Metabolic regulation

Metabolism is a chemical process where food and drink are turned into energy. Metabolic reactions, especially those involved in digestion, follow circadian rhythms.

5 – 15% of the genes in digestive tissue vary in expression according to circadian rhythms. Several of these genes are involved in metabolizing sugars and fats8. When you’re anticipating a meal, your stomach releases ghrelin, the hunger hormone. This hormone informs the hypothalamus that it’s time to stop metabolizing fats, and awaken your appetite9.

How do Circadian Rhythms Affect Aging?

These rhythms are critical since they prepare our body for physical activity, food, sleep, etc. When these processes are erratic, the body is caught by surprise and sometimes, unable to adjust. You might find yourself hungry all the time, or unable to sleep!10.

Without consistent sleep, and a healthy food regimen, sleep quality and digestive efficiency suffer. Poor quality sleep and irregular food intake are known to accelerate aging and trigger epigenetic alterations. (Read more about epigenetics and aging here.)

While consistent circadian rhythms promote health and longevity, disrupted rhythms are associated with age-related diseases such as cancer, cardiovascular disease, and metabolic disorders12.

How do Circadian Rhythms Affect Your Biological Age?

Circadian Rhythms impact our epigenome, and our epigenome impacts our biological age. As our circadian rhythms become irregular, our lifestyle changes. Irregular sleep and lack of sleep are known to influence our epigenetics and increase our biological age13.

How to Reset Your Circadian Rhythm?

There are several tips and tricks you can integrate into your daily, or shall we say circadian, routine!

1. Spend time outdoors so the light can wake you up

2. Exercise in the morning or day and avoid late-night workouts

3. Sleep in the dark to promote natural melatonin production

4. Avoid taking alcohol, caffeine, nicotine, or sugary foods in the evening

5. Avoid screens before bedtime and remember that screen time too close to bedtime negatively impacts your sleep

6. Avoid naps in the afternoon and evening13

Screen-time

A common culprit of circadian disruption is screen time before sleep. Blue light in particular evokes a very strong response from your SCN, which can linger long after you’ve put your devices away. This activity interferes with melatonin production in the body and can make it difficult to achieve deep sleep3.

It’s highly recommended to stop using devices within 30 minutes of bedtime. If using your device cannot be avoided, try to keep the screen further away and consider investing in a pair of blue light filtering glasses. You can also use a night shift setting on your phone and computer to avoid blue-light intake and straining your eyes14.

Essentially, your body has a natural itinerary for the day. To enhance well-being and promote longevity it’s important to pay attention to your internal routine.

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Takeaways.

  • Headquartered in the hypothalamus, a small region in the brain, circadian rhythms regulate and synchronize our 24-hour cycle of biological processes.
  • Hormones are critical to sleep times. In the evening, the hypothalamus stimulates melatonin production to encourage sleep. Cortisol levels are stimulated during the day to wake us up.
  • 5 – 15% of the genes in digestive tissue vary in expression according to the circadian cycle, several are involved in metabolizing sugars and fats.
  • Disrupted circadian rhythms are heavily associated with age-related diseases such as cancer, cardiovascular disease, and metabolic disorders.
  • Resetting the circadian clock can promote longevity and reduce biological age.

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