Coronavirus: What day of the week is it again?

Your body clock helps keep you healthy. So how can you wind it during lockdown?

Keeping those internal clocks well oiled is a key to good health, and building timely exercise, food and sleep into our days and nights can help

For many of us, the coronavirus pandemic has thrown usual routines out the window. Yet, while we can mentally lose track of days, our body clocks are keeping the score. Keeping those internal clocks well oiled is a key to good health, and building timely exercise, food and sleep into our days and nights can help.

That's according to Dr Annie Curtis, who researches how daily rhythms affect the immune system. "Your body clock is your internal timekeeping mechanism, it tells your body the time of day," says Curtis, a lecturer at the Royal College of Surgeons in Ireland.

Internal timekeeping

The cells that make up our body don’t count out seconds, minutes and hours like the clock on the wall, she explains. Instead, they monitor various proteins whose levels fluctuate across the day and night.

“In some cases there will be high levels of a particular protein during the daytime, and the cell can sense that and so it knows it is daytime,” says Curtis. “Then as we move into evening and night, the protein levels change, signalling to the cells that we are heading for a time of sleep.”


In recent years, the importance of having a synchronised body clock has been coming to light, says Curtis. “The body clock underlies the performance of everything – your digestion, your hormones, your blood pressure and heart function and how your body grows and repairs,” she says. “And perhaps most relevant for the Covid-19 pandemic, the body clock has a crucial input into lung function, which drops naturally at night, and the immune system, which primes and prepares itself when you sleep.”

Royal College of Surgeons in Ireland lecturer Dr Annie Curtis, who researches how daily rhythms affect the immune system

Curtis and her colleagues in RCSI have been examining the role of the body clock in front-line defensive immune cells called macrophages, which gobble up invaders such as bacteria and viruses, and dendritic cells, which gather information about infectious agents and help us to build immunity against them. "These macrophages and dendritic cells are the ones you need at the party when the virus is calling," she says. "And we are seeing that if the body clock is disrupted, these defensive immune cells do not function as well as they should."

Light, exercise and food

So how can we wind our body clocks effectively, particularly at a time when changes in work, school and recreational activities are less likely to structure our days? There is plenty we can do, says Curtis.

Light is the master conductor of the body clock, she explains, and we can harness it as much as possible. “When daylight enters your eyes it sends signals to a specific part of your brain that calibrates the body clock, so getting some daylight in the morning is useful.”

She acknowledges that we might not be getting as much daylight as we used to: “Before this, maybe you got outdoors in the morning on your commute to work or bringing the kids to school, and now that is not happening,” she says. “So you might need to make a conscious effort to spend some time outside in the morning – going for a walk or even eating breakfast out in the garden or on the balcony if that is an option.”

Sitting close to a window in the morning is a good substitute, she adds. “I did a quick experiment with a light meter in my own house and found that outside in the garden on a sunny day was 50,000 lux, but in a darkened corner inside the levels were only about 100 lux. That figure rose considerably when I went over to just inside the window, which was 1,000 lux, so if you are indoors in the morning, try to be in the brightness near a window.”

Exercise is another excellent way to tune the body clock, and morning exercise particularly so. “Exercise at any time is good of course,” says Curtis. “But if you can be active in the morning, especially outside, that provides an anchor for your body clock as well as boosting your feelings of wellbeing.”

When we eat is also a powerful signal to the body clock, and Curtis recommends trying to stick to a reasonably regular schedule. “I know it is hard, I am finding this myself, when you are home all day the temptation is to graze or be looser with the mealtimes,” she says. “But having regular mealtimes is better for your body clock, and try not to eat too late at night.”

Sleep for your immune system

Sleep is a balm for health in general, and for the immune system it is a time of important and distinct activity, notes Curtis. “The research shows that during sleep the cells of the immune system are out moving around in the bloodstream, they are creating an immune memory of what they have seen that day and they are preparing to protect you against that threat should you encounter it in the future,” says Curtis.

“So you want to be preparing well for a good night’s sleep, and that means minimising your time looking at the light of a screen and avoiding that wine in the evening, because alcohol can disrupt your quality of sleep. Try to get to sleep at the same time each night too, in fact I would recommend that you set your alarm clock for a consistent and early time to go to sleep, rather than one to wake you up in the morning.”

Tips to wind your body clock while at home during the Covid-19 pandemic

– Face some daylight in the morning – if you can’t go outside, sit near a window

– Exercise, in the morning if possible

– Eat at regular mealtimes, and don’t eat late at night

– Set an alarm clock to go to sleep at the same time each night