Heading off for a night under canvas? Make sure you pack the sleep masks.
Turns out that exposure to even moderate light at night can harm your cardiovascular function during sleep and increase your insulin resistance the following morning.
‘It's important for people to avoid or minimise the amount of light exposure during sleep,’ says Dr Phyllis Zee, chief of sleep medicine and author of new research at Northwestern University. ‘The results from this study demonstrate that just a single night of exposure to moderate room lighting during sleep can impair glucose and cardiovascular regulation, which are risk factors for heart disease, diabetes and metabolic syndrome.’
If you're able to see things really well,
it's probably too light
With up to 40 per cent of adults (and likely even more children) sleeping with a light on in the bedroom, bright nights are common. But how light is too light? ‘If you're able to see things really well, it's probably too light,’ advises Zee.
The study tested the effect of sleeping with 100 lux (moderate light) compared to 3 lux (dim light) in participants over a single night. Researchers revealed that moderate light exposure caused the body to go into a higher alert state. In this state, the heart rate increases as well as the force with which the heart contracts and the rate of how fast the blood is conducted to your blood vessels for oxygenated blood flow.
We already know that light exposure during daytime increases heart rate by kick-starting the sympathetic nervous system, which shifts your heart into high gear and heightens alertness to meet the challenges of the day.
‘Our results indicate that a similar effect is also present when exposure to light occurs during night time sleep,’ Zee explains. The study showed heart rate increasing when sleeping in a room that’s moderately lit.
‘Even though you are asleep, your autonomic nervous system is activated,’ explains Dr Daniela Grimaldi, assistant professor of neurology at Northwestern. ‘That’s bad. Usually, your heart rate together with other cardiovascular parameters are lower at night and higher during the day.’
Researchers also found insulin resistance occurred the morning after people slept in a light room. Insulin resistance is when cells in your muscles, fat and liver don't respond well to insulin and can't use glucose from your blood for energy. To make up for it, your pancreas makes more insulin. Over time, your blood sugar goes up. Previous studies a have also shown that healthy people who had exposure to light during sleep tend to be more overweight and obese.
You may not notice you feel worse after sleeping when it’s too light, but the brain senses it. ‘It acts like the brain of somebody whose sleep is light and fragmented,’ says ‘Grimaldi. ‘The sleep physiology is not resting the way it's supposed to.’
Tips for better sleep
So what’s the solution? If you’re investing in a new tent this season, look for one with a ‘blackout’ room. Our Coleman Mackenzie 6 Blackout Tent (which I can’t rate highly enough) has a blackout pod for four, which the kids sleep in. It is brilliant. Even when my husband and I are woken at dawn by the bright morning sun, the kids carry on snoozing, blissfully unaware of the sunrise.
If you’re staying indoors, invest in some blackout blinds, especially for during the summer months. We travel with a couple of Gro Anywhere Blackout Blinds, lightweight blackout blinds that fit most windows and simply fix to the glass with suckers. If your kids need to have a light on, make it a dim light that is closer to the floor. And aim for an amber or a red/orange light which is less stimulating for the brain. Don't use white or blue light and keep it far away from the sleeping person.
