Circadian Rhythm
Your circadian rhythm is your body's internal 24-hour clock. It influences when you feel awake, alert, sleepy, hungry, and even affects hormone release and body temperature.
What Is a Circadian Rhythm?
A circadian rhythm is a natural biological cycle that repeats approximately every 24 hours.
It helps coordinate important body functions so they occur at the most appropriate times of day.
Your Internal Body Clock
Deep within the brain is a small region called the suprachiasmatic nucleus (SCN), located in the hypothalamus.
This area acts as the body's central clock and receives signals from the eyes about light and darkness.
- Light signals encourage wakefulness.
- Darkness encourages sleepiness.
- The clock helps regulate daily biological functions.
A Typical Circadian Day
Morning
- Cortisol rises to promote alertness.
- Body temperature begins increasing.
- Energy and concentration improve.
Afternoon
- Most people experience peak alertness.
- Physical performance is often strongest.
Evening
- Body temperature begins falling.
- Melatonin production starts increasing.
Night
- Melatonin levels remain elevated.
- Sleepiness increases.
- Sleep becomes easier.
Why Light Matters
Light is the strongest influence on the circadian rhythm.
- Morning light helps set the body clock.
- Daylight improves alertness.
- Bright light at night can delay sleep.
- Screen use before bed may affect some people.
What Can Disrupt Circadian Rhythms?
Several factors can interfere with the body's natural timing system.
- Shift work
- Jet lag
- Irregular sleep schedules
- Excessive evening light exposure
- Frequent overnight awakenings
When the body clock becomes misaligned, sleep quality may decline, and daytime fatigue may increase.
Circadian Rhythms and Ageing
Circadian rhythms can change as people get older.
- Sleepiness may occur earlier in the evening.
- People may naturally wake earlier.
- Sleep can become lighter and more fragmented.
These changes are common and do not necessarily indicate a sleep disorder.
Why Circadian Rhythms Matter
A healthy circadian rhythm supports:
- Better sleep quality
- Improved concentration
- Mood regulation
- Metabolic health
- Immune function
- Physical performance
Key Takeaways
- The circadian rhythm is the body's internal 24-hour clock.
- Light is the main signal that regulates the body clock.
- Melatonin rises in darkness and helps prepare the body for sleep.
- Irregular schedules can disrupt circadian rhythms.
- Healthy circadian timing supports sleep, health, and wellbeing.