Why do we feel hungry at mealtimes and not in the middle of the night?

Without having to think about it, our physiological routines and rhythms are governed and controlled by an internal timekeeper that maintains a 24-hour circadian cycle (“circa” is Latin for “about” or “approximately”, and “diem” is Latin for “day”). This cycle ensures that our activities keep pace with the constant rotation of the planet we call our home.

The circadian cycle hums along automatically thanks to an area of our brain known as the suprachiasmatic nucleus. Though tiny, this region hosts an intricate mechanism of gene and protein interactions that run in an approximately 24-hour period. The cycle is self-sustaining and serves as our master biological clock.

Interestingly, the timing of this clock can be quite different between individuals depending on genes, age, light exposure, and other environmental cues. This is why some people are “night owls” who are more active late in the day and go to sleep in the early hours while others are “morning larks” who have the opposite pattern of activity. Young people tend to have later body clocks while older people generally prefer to go to sleep and wake up earlier.

Understanding circadian rhythm disorders

Several sleep disorders can occur due to disruptions or misalignment of the internal circadian clock. Although some of these might be confused with insomnia disorder, they do not develop due to the same reasons as insomnia and often require a different approach.

One example of a circadian rhythm disorder is Delayed Sleep Phase Syndrome (DSPS). Individuals with DSPS struggle to fall asleep at conventional bedtime hours, often leading to a later-than-normal sleep-wake cycle. When teenagers have these symptoms, parents may conclude that their kids are being lazy or rebellious. On the contrary, it can be challenging for young people to deal with the delay in their body clock, especially when they have to wake up very early to get to school. The combination of late bedtimes and early rise times can cause teenagers to be chronically sleep-deprived, impacting mood, concentration, and school performance. In some individuals, DSPS can persist into early adulthood and continue to cause problems for those who have to clock in to work at a fixed time.

Conversely, Advanced Sleep Phase Syndrome (ASPS) manifests as an early onset of sleep and awakening, causing individuals to feel drowsy during the evening hours. This problem does not usually interfere with school or work obligations as DSPS does, but it may interfere with a person’s social life and can be associated with feelings of loneliness or depression.

Another disorder of the circadian system is known as Shift Work Sleep Disorder (SWSD), a prevalent problem that afflicts individuals whose work schedules deviate from the traditional nine-to-five routine. It predominantly affects professions that require round-the-clock coverage, such as healthcare, transportation, hospitality, and manufacturing. Shift work often demands that an individual sleep at times that are misaligned with their body clock, leading to difficulties initiating and maintaining sleep during these non-traditional hours. The problem is often worse for those who work irregular shifts. In 2007, the International Agency for Research on Cancer (IARC) classified shift work that disrupts the body clock as “probably carcinogenic to humans”, highlighting that a circadian disorder should not be dismissed as “just a sleep problem”.

Managing circadian disorders

Individuals with circadian disorders and shift workers in particular should take extra care to manage their sleep hygiene. If sleeping during the day is a necessity, it’s worth investing resources into making sure your sleeping environment is totally dark and as quiet as possible. Eye masks, earplugs, and noise-canceling headphones can be useful for this. Limiting exposure to stimulation in the hour before sleep is also especially important.

If you or your child are suffering from DSPS, some options are often overlooked. For example, light therapy involves the use of bright artificial light to help realign circadian rhythms. It involves exposure to specific wavelengths of light, mimicking natural sunlight, to regulate sleep-wake patterns. Light is the most important cue that the suprachiasmatic nucleus uses to set its rhythm. By strategically timing light exposure, individuals can synchronize their internal clocks with desired sleep schedules.

Alternatively, chronotherapy involves gradually adjusting sleep schedules over several weeks to synchronize with desired wake-up times. By systematically shifting bedtime and wake-up times in small increments, the body gradually adapts to the new schedule, mitigating the impact of circadian rhythm disruptions. Think about this as adjusting slowly to jet lag, except that the “time zone” you are adjusting to is the one set by your internal clock!

With a little bit of help from a sleep psychologist, the impact of circadian disorders on daily living can be minimized or eliminated altogether. If you suspect you are suffering from a circadian disorder or are having other problems with your sleep, reach out to us today to talk through your options.