If you’ve lived much of your life quietly amazed at people who can function before noon and fall asleep before midnight, you may belong to a relatively small category of people known as "night owls," or "evening-types" in the scientific literature.
Night owls tend to naturally stay up late into the night, sleep in, and feel most alert and energetic in the afternoon and evening. Larks, on the other hand, like to go to bed in the early evening, get up early, and feel most alert in the morning. If you think you finally have a scientific excuse for sleeping in, you may be right, but not so fast—keep in mind most people are neither owls nor larks, but somewhere in between.
Being a morning or evening person seems to be the expression of a variation in one’s circadian rhythm, which is a roughly 24-hour cycle our bodies follow to regulate alertness, body temperature, appetite, and other important functions. Your circadian rhythm is partially dictated by external factors, like light, but also depends on an internal clock, which is what’s responsible for these variations. The research on how exactly this works is ongoing.
The majority of people are neither a night owl nor lark. The percentage of people in each category varies by study, but the general estimate is that around 10-15% of people are night owls, 20-30% are larks, and 55-70% of people are in the intermediate category.
Some research suggests that your chronotype can affect more than when you feel most energetic—there seem to some actual behavioural differences between the types. For instance, night owls are more likely to smoke, drink alcohol, and be less physically active. Interestingly, they may also be more intelligent, contrary to the folk wisdom that says early to bed and early to rise makes one… well, you know the rest.
Though these are certainly not easy to separate, remember to consider whether it’s your natural inclination or your lifestyle that’s responsible for your sleep/wake patterns. If you’re lucky enough to have a holiday where your schedule isn’t intervened upon by work or other obligations, that would be a good time to figure out your natural rhythm.
We’ll caution you that the research on these variations is far from conclusive, so it’s safest not to jump to conclusions. The golden rule of thumb is that you need 7-9 hours of sleep every night for optimal health.
Otherwise, listen carefully to your body to work out a schedule that feels best for you.