Alaska Sleep Education Center

Summer Solstice and Circadian Rhythm

Posted by Jennifer Hines

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on Jun 21, 2018 4:00:00 AM

Since today is the longest day of the year, it seems appropriate to discuss circadian rhythm and the role that daylight plays in our sleep cycle. 

Your circadian rhythm is an ingrained biological clock that regulates the timing periods of tiredness and wakefulness throughout the day. Your body clock is calibrated by the appearance and disappearance of natural light in a 24-hour period. The term circadian is derived from the Latin "circa diem" meaning "approximately a day."

The functions of your circadian rhythm are based in the part of the brain known as the hypothalamus. Within the hypothalamus are a group of cells known as the suprachiasmatic nucleus (SCN), which is connected to our optic nerves that sense changes in light. The SCN is also responsible for regulating many body functions that revolve around the 24-hour cycle including: body temperature, heart rate, blood pressure, and the release of hormones such as melatonin which helps us with sleep.

How Your Body Clock Works














In the mornings when light first hits our eyes, our body temperature and blood pressure begin to rise, our heart rate increases, and there is a delay in the release of melatonin which helps us wake up. Throughout the day our circadian rhythm increases and even has a dip during the day before decreasing at night as our body functions slow down and melatonin begins to release again to help us sleep again.

For most people, the body clock is set for sleep to begin around 11 p.m. and make us rise around 7 a.m. Although there is some deviation for each individual this clock is the standard norm. Most people are sleepiest between 2-4 a.m. and again between 2-3 p.m. (although most rarely nap), and most alert in the early mornings and late afternoons.

Some people's circadian rhythms just aren't the same as others, and their body responds differently at times that are irregular to others. Other people must work jobs or have school schedules outside of normal times to meet the growing demands of a 24-hour society. Conflict is created when people's circadian rhythms don't sync-up with everyone else's.

So what happens when a person's circadian rhythm is disrupted by external forces or circumstances (demands from jobs, schools, or travel) or their own biological clock is offset from the majority of society?

People begin to develop circadian rhythm sleep disorders, and if left unchecked can lead to issues ranging from exhaustion and confusion to medical problems such as obesity, diabetes, depression, and dementia.

Circadian rhythm is, at its most basic, the 24-hour wake and sleep cycle your body follows based on night/dark and day/light. It’s a lot more complex than that, of course, with your pineal gland releasing melatonin at nighttime and a whole host of other hormones and chemicals involved, but for the sake of simplicity, we’ll keep it general. 

So what happens when your daylight cycle has wild fluctuations, as it does in Alaska.

Not surprisingly, your circadian rhythm can get out of whack. When it’s light out all night, it is difficult to fall and stay asleep, and you may feel “tired but wired.” On the opposite end is Alaskan winters, where it is barely light out – in December and January, you might feel like a zombie.

There are ways to balance your circadian rhythm with the madly fluctuating daylight. In winter, a full-spectrum light box helps stimulate daylight, while in summer black-out curtains or a sleeping mask (and a regulated bedtime) help block the sun.

Keeping a regular schedule year-round will help keep your rhythm stable, which in turn will keep you healthier. 

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Topics: summer

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