A. The natural world is dominated by cycles that are constant and repeated — the moon’s rotation around the earth, the changing of the seasons, the changes between night and day. It is these cycles or rhythms that in part control changes in our metabolism, mood and behaviour, and even the patterns of our sleep.

B. The circadian rhythm is the cycle that indicates when to be awake and when to be asleep. This is a daily cycle that is controlled by changes in amplitude (highs and lows) of light and temperature. As day turns to night, the sun sets and it becomes cooler. The triggers of less light and lower temperatures signal to the body that it is time to slow and begin the pattern of sleep. Of course, there may be many hours between sunset and the time people actually go to bed, but it is from this time that we generally become increasingly less alert and reaction times can be noticeably slower.

C. There are a number of factors that can affect our circadian rhythm. Working night shifts, which requires people to act in contradiction to the body’s natural rhythm, is perhaps the most damaging. Despite getting a good 8 hours sleep during the day, night shift workers still tend to feel drowsy for at least some of the night. This is the main factor for the increase in workplace accidents on this shift when compared to the day shift. The seasons can also affect our natural rhythm, with people having less energy during winter months when there is less sunlight and warmth to stimulate the brain. International travel, notably when travelling in excess of 4 hours, can also have a significant effect; in extreme cases, it can take up to 7 days for your rhythm to reset due to this, a phenomenon referred to as jet lag. A similar, although milder, effect can be felt in countries with daylight savings time, when the clocks are moved forward and backward depending on the season.

D. There are some tips for helping your body work with your circadian rhythm. First thing in the morning take a short walk outside or open all the curtains to get as much light as possible through the eyes and into the brain. Lighting levels that affect circadian rhythm in humans are higher than the levels usually used in artificial lighting in homes. In addition to the strength of the light, wavelength (or colour) of light is a factor, the best being that present in sunlight. Plan your work and other activities around the highs and lows of your temperature rhythm. For example, plan easier activities for first thing in the morning when you’re not operating at your physical best. Late morning is better for challenging tasks. After lunch you may feel like nodding off. Take scheduled breaks. The best time to exercise is in the late afternoon — your body temperature reaches its daily high, it is warmed up and stretched from spending your day at work. Avoid driving during sleep times. Sleepy drivers should stop for a nap — playing loud music or leaving windows open is an overrated misconception. At night, close the blinds and curtains and sleep in a dark room. If you work the night shift, use bright lights and music in the workplace to keep your brain alert. Wear an eye mask to block out the light when you want to go to sleep.

E. Every human — in fact, most non-nocturnal animals — follow the basic rules of the circadian rhythm. However, we also have our own unique body clocks which control the daily changes in how we think and feel, and oversee a number of our personal characteristics such as sleep patterns. Your body clock dictates whether you are a night owl, happy to work late into the night, an early bird who prefers the morning or a humming bird, happy to work both ends of the day. Your body clock determines not only your personal sleep patterns, but also whether or not you are grumpy before you have your morning coffee, when and what you need to eat throughout the day, whether you work better in the morning or the afternoon and the best time for you to do exercise. It also affects physical performance, such as temperature, blood pressure, digestion, hormone levels and brain activity (such as mood, behaviour, and alertness). Your body clock is what causes you to gain a few kilograms in autumn and winter time and to make it easier to lose weight in spring and summer.

F. Being aware of a few issues can help us maintain the best rhythms for our body clocks, but there are some tips and tools that can help. Keeping to the same bedtime routine and wake-up schedule, even on your days off, is particularly important — there should be no more than a few hours difference in the time you go to bed. Avoiding interruptions to your sleep is also very important. If there is intermittent, irregular noise, use a fan or any white noise device that generates calming sounds. This is particularly important for night shift workers, for whom daytime noises are generally louder; soft, background noise can help drown out daytime activity noises. Eat small frequent meals to help stoke your metabolism. This is not only helpful in weight maintenance, but reinforces the “day” phase of your circadian clock. Eat most of your energy foods earlier in the day and avoid eating a heavy meal near bedtime. Avoid all-nighters, like studying all night before an assessment. Cutting back on sleep the night before may mean that you perform less well. Reduce changes to your work shift, such as changing from night shift to day shift. Avoid alcohol and cigarettes before sleep time. If you feel sleepy during the day, take a short nap. Set an alarm so you sleep for no more than about 20 minutes. Anything more than just a ‘catnap’ and you will enter into Stage 3 (deep sleep) and find it harder to wake up from.