Some people wake up naturally at 5 AM, feeling ready to start the day before the alarm even rings. Others may sleep until 9 or 10 AM and still feel like their brain needs more time to switch on. It is easy to blame this difference on habits or discipline, but there is another factor quietly influencing when we sleep and wake which is our genes.
Inside every cell in the body is a biological clock that follows a roughly 24-hour cycle called the circadian rhythm. It helps coordinate sleep, body temperature, hormone release, metabolism and many other processes. Light is one of its strongest signals, helping the brain adjust this clock to the day and night cycle. At the centre of this system are several clock genes, including PER1, PER2 and PER3. These genes help produce proteins that build up inside cells and eventually switch off their own production. As the proteins are broken down, the cycle begins again. This molecular feedback loop takes roughly 24 hours and helps keep the body’s internal clock running. Small genetic differences can shift the timing of this cycle. These differences contribute to a person’s chronotype where their natural tendency to be more active and alert earlier or later in the day. Early chronotypes tend to become sleepy earlier and wake earlier, while late chronotypes naturally prefer later bedtimes and wake-up times.
But genes are not the whole story. Exposure to light, meal timing, physical activity, work schedules and age can all influence the body clock. Teenagers, for example, often experience a natural shift toward later sleep and wake times, while many older adults tend to become earlier risers. This explains why forcing everyone onto the same sleep schedule can be difficult. A person who naturally functions best late at night may struggle with a 6 AM routine even if they get enough sleep.
Researchers are studying the circadian genes to understand how differences in biological timing affect sleep, health and disease. The goal is not to decide whether early birds or night owls are better. It is to understand that our bodies do not all run on exactly the same schedule. So, if waking up at 5 AM feels effortless to someone while 10 AM feels early to another, it may not be a matter of willpower. Their internal clocks may simply be ticking at different times
