Not to be all gothic and theatrical, but the darkness is coming. Come the end of October, the clocks go back. Suddenly, the Sun will set before 5pm and we’ll walk around in astonishment as though it hasn’t happened every year previously.
The shock is real, however; we feel it in our very cells. That’s because the shift in our external clocks has an impact on our bodies’ internal clocks, the circadian rhythms that underpin more aspects of our health and behaviour than many of us realise.
Most of us feel the clocks change with little more than seasonal jet lag. We’re groggy and grumpy.
At the population level, however, we see something more serious. Every October and March, there’s a slight change in the incidence of heart attacks and stroke.
“It’s more in March that the real problems arise, but going back is also not ideal,” says Dr John O’Neill, who studies circadian rhythms at the Medical Research Council Laboratory of Molecular Biology. “When the clocks go forward, there’s maybe a 25-per-cent increase in the incidence of heart attacks.”
Scientists don’t know exactly why this happens, but disruption to our circadian rhythm is the chief suspect. It’s thought to affect things like sleep, blood pressure and cortisol levels, all of which contribute to the risk of a heart attack.
But it’s not just the cardiovascular system that’s suddenly out of sync. Body clock disruption is also linked to mental health issues like depression and anxiety, immune function, sleep quality and muscle strength.
There’s also a higher risk of car accidents, O’Neill says. “The circadian clock regulates how able we are to maintain concentration. So, for a few days before the circadian clock has adjusted, people may be that bit more sleepy, that tiny bit more likely to have a lapse in concentration or reaction times.”
O’Neill is clear that the risk is real but small, especially if you’re young and healthy. The wider point is that we should be paying better attention to our circadian health than many of us are, because it affects a number of long-term risk factors.
We can start by thinking of the clock change like seasonal jet lag. Flying to another time zone where you’re suddenly eating and sleeping at different times has the same discombobulating effect on your body. So, to make the circadian gear shift easier, we can adopt the same techniques we use to beat jet lag.
“If you want to shift your circadian clock more quickly – it’s quite intuitive really – be sensible about the times when you see light and eat food,” he says.
“The problem when you’re on a flight over the Atlantic, for example, is that people watch some movies and eat whatever food they’re given. That sends a very confused signal to the circadian clock.”
To limit the effect of that confusion, you could work out the timing of dawn in your destination (so, when your new morning is going to be) before you board the plane.
“If possible, try to avoid seeing any bright light or eating anything before dawn in your destination,” O’Neill says. “Then whether you’re still on the flight or you get to where you’re going, that’s the time you want to be seeing bright light and have a hearty breakfast.
“Those two signals will reset your circadian rhythm much more quickly than if you just rely on light or time of feeding alone.” And the same principle applies, albeit more subtly, to changing the clocks back.
But however miserable we might feel about the end of British Summer Time, it’s a useful reminder that our internal clocks need tuning far more than the ones hanging on our walls.
O’Neill believes we should abolish changing the clocks altogether and says the majority of his colleagues in sleep and circadian research agree.
“There’s not a good argument to continue it in this day and age,” he says. It would be better to look after our circadian health like we look after our cardiovascular health.
“What that means is following a similar routine each day,” O’Neill says. “Waking up at about the same time, eating meals at roughly the same time. Avoiding bright light and not eating in the middle of the night. Exercising in the daytime, not at night."
"The last 50 years of research have really hammered home that good circadian health is required for ageing well and extending our healthspan.”
Read more:
