We all know that getting enough sleep is important for our health. What science is now beginning to reveal is that having a regular sleep pattern may be even more crucial. Not sticking to a consistent bedtime and wake-up schedule has been linked to a heightened risk of a range of health problems.
The latest research comes from Jean-Philippe Chaput of the University of Ottawa. He drew on data from 72,269 people aged 40-79 who were taking part in the UK Biobank study, none of whom had a history of major cardiovascular events. They wore an activity tracker for seven days to record their sleep. Then, for the next eight years, their incidents of cardiovascular death, heart attack, heart failure and stroke were collected from death registries and hospital records.
After accounting for a range of potentially influential lifestyle factors including physical activity levels, fruit and vegetable intake, alcohol consumption and smoking, irregular sleepers were 26% more likely to have a major cardiovascular event than those with a regular sleep-wake cycle. Moderately irregular sleepers were 8% more likely to do so.
Chaput says the ideal is to go to bed and wake at the same time, plus or minus 30 minutes.
“The wake-up part seems to be even more critical than the bedtime,” he explains. “People tend to catch up on sleep by having a lie-in on the weekend, but that might not be a good thing.”
Moderately irregular sleep is considered plus or minus one hour, and more than one hour counts as irregular.
“It’s a pretty narrow window,” concedes Chaput. “There’s not a lot of leeway. But even if you sleep the recommended 7-9 hours a night, if you don’t go to bed and wake up at the same time every day, it could be bad for you in the long term.”
The occasional late night or sleep-in isn’t likely to cause a problem; it is having irregular sleep patterns over a long period that seems to do the damage.
The effect that researchers saw was remarkably linear – the worse the sleep pattern, the higher chance a person had of experiencing a cardiovascular event.
Scientists are still investigating exactly what is going on in the body, but it seems likely it is linked to the brain’s master clock, a group of nerve cells called the suprachiasmatic nucleus, which regulates most circadian rhythms and controls the release of sleep-wake hormones. When we work against this central pacemaker, it affects hormones and puts stress on the metabolic system, leading to poorer health over time.
One Harvard University study found people with inconsistent sleep schedules are at significantly higher risk of diabetes. Variability in sleep timing has also been linked to a greater chance of high cholesterol and hypertension. And research from Monash University has shown that people with very irregular sleep patterns may be more likely to develop dementia.
All of this is bad news for shift workers, and the research suggests it might be healthier for them to stick to the same sleep pattern on days off. Since that is unlikely to be practical, Chaput advises focusing on eating well and exercising to try to minimise the negative health impacts of sleep irregularity.
There is no ideal time to go to bed and wake; that depends on chronotype. Some of us are early birds and others are night owls. But the brain’s master clock uses light and dark as cues, so it is important for everyone to be exposed to light within 20 minutes of waking every morning and to stay off screens within an hour of bedtime.
“The best tip I can give for a good, restful sleep is to be active every day, especially outside,” says Chaput. “With screens, the problem isn’t only the blue light they emit, but the way they stimulate the brain. With this epidemic of physical inactivity, when people go to bed, the brain is wired but the body isn’t tired.”
There are stages of life when sleep tends to be more erratic – if there is a newborn in the house, for instance – but Chaput says, if possible, we should try to establish a routine and stick to it.
“We have tended to see the main pillars of health as eating well and exercising, and sleep has been lagging behind. In some cultures, it’s even seen as a waste of time. While it may take a few weeks to adjust, people need to prioritise regular sleep.”
