Apple’s Night Shift tool does NOT help you sleep: iPhone feature that adjusts the screen’s colours to warmer hues after sunset has no effect on ability to fall asleep or quality of your snooze, study claims

  • Night Shift cuts short-wavelength light emissions to improve iPhone users’ sleep
  • But experts found ‘no differences in sleep outcomes’ attributable to the iOS tool
  • Blue light is emitted by LED lights in smartphones, tablet computers and laptops 

Apple’s iOS tool Night Shift may make your screen darker, but it does not improve sleep, a new study claims.

US researchers from Brigham Young University found it had no effect on volunteers’ ability to fall asleep and stay asleep, or the quality of their sleep.

Night Shift, which was introduced by Apple in 2016 for iOS 9.3, is built into Apple software and filters short-wavelength blue light after sunset to optimise sleep. 

Blue light, which is emitted by the LED lights used in smartphones, tablet computers and laptops, is known to be particularly disruptive to a good night’s rest. 

Blue light, which is emitted by the low-energy light-emitting diodes used in smartphones, tablet computers and laptops, is known to be particularly disruptive to sleep 

WHAT IS NIGHT SHIFT? 

Night Shift is an app for Apple devices.

It uses the clock and geolocation of your device to determine when it’s sunset in your location.

Then it automatically shifts the colours of your display to warmer colours. 

In the morning, it returns the display to its regular settings. 

Night Shift is built-in to Apple devices, meaning it doesn’t have to be downloaded.

It can be found under ‘Display & Brightness’ in ‘Settings’. 

‘Apple’s iPhone Night Shift feature purports to reduce short-wavelength light emissions and improve sleep,’ the experts, from Brigham Young University (BYU) in Utah, say in their paper, published in Sleep Health. 

‘Across our full study sample, there were no differences in sleep outcomes attributable to Night Shift.’  

Night Shift filters out blue light, which is simply part of the visible light spectrum – what the human eye can see. 

It’s widely believed that the emitted blue light from phones and other electronic devices like computer monitors and fluorescent bulbs disrupts melatonin secretion and sleep cycles.   

Night Shift adjusts the screen’s colours to ‘warmer’ orangey-red hues after sunset by default, although users can manually select what time of the day it’s activated.  

For their study, researchers recruited 167 adult iPhone users between the ages of 18 to 24, who used their phones daily.

Participants were randomly assigned to one of three conditions that dictated their iPhone use during the hour preceding bedtime for seven consecutive nights.

Participants either used their phone at night with the Night Shift function turned on, used their phone at night without Night Shift, or did not use a smartphone before bed at all. 

Sleep outcomes – including sleep duration and ‘sleep latency (the amount of time it takes to fall asleep after the lights have been turned off) – were tracked using wrist-worn accelerometers. 

Participants were asked to spend at least eight hours in bed, while the individuals who were assigned to use their smartphone also had an app installed to monitor their phone use. 

Night Shift (pictured) reduces the amount of blue light emitted from your device around bedtime. It uses the clock and geolocation of your device to determine when it’s sunset in your location

‘In the whole sample, there were no differences across the three groups,’ said study author Chad Jensen, a psychology professor at BYU. 

‘Night Shift is not superior to using your phone without Night Shift or even using no phone at all.’

Researchers then conducted a further analysis of the individuals who fell above and below 6.82 hours, the median for total sleep time.  

They split the sample into two separate groups – one that averaged about seven hours of sleep and another that slept less than six hours each night.

The group that got seven hours of sleep, which is closer to the recommended eight to nine hours a night, saw a slight difference in sleep quality based on phone usage. 

In this sample, individuals who did not use a phone before bed experienced superior sleep quality relative to both those with normal phone use and those using Night Shift.

This suggested no phone use at all was conducive to a longer night’s sleep. 

‘Those who abstained from smartphone use before bed showed better sleep quality (more efficient sleep, less time awake during the sleep hours) compared to those who used their phones with or without Night Shift,’ Professor Jensen told MailOnline.

‘Night Shift was no better than no Night Shift in this regard.’ 

Within the six-hour group (containing people who had the least amount of sleep) there were no differences in sleep outcomes based on whether the participants used Night Shift or not.  

‘This suggests that when you are super tired you fall asleep no matter what you did just before bed,’ said Professor Jensen. 

‘When you are short on sleep, it doesn’t appear to matter whether you use a phone (with or without Nigh Shift) before bed, likely because the pressure to sleep is so high. 

‘The sleep pressure is so high there is really no effect of what happens before bedtime.’

The results suggest that it is not blue light alone that creates difficulty falling or staying asleep, according to the team. 

BYU says: ‘Night Shift may make your screen darker, but Night Shift alone will not help you fall or stay asleep’ (stock image)

‘Psychological engagement’ from texting, scrolling and posting is another important factor that affect sleep outcomes, they claim. 

‘I wouldn’t say that blue light exposure doesn’t affect sleep at all – many laboratory studies would suggest that it does,’ said Professor Jensen. 

‘Rather, the effects of blue light exposure likely act in concert with many other environmental and behavioural factors, including your habitual sleep and other stimulating components of smartphone use.

‘While there is a lot of evidence suggesting that blue light increases alertness and makes it more difficult to fall asleep, it is important to think about what portion of that stimulation is light emission versus other cognitive and psychological stimulations.’ 

MailOnline has contacted Apple for comment.  

BLUE LIGHT: POSITIVE AND NEGATIVE EFFECTS 

Short-wavelength, high-energy blue light scatters more easily than other visible light and can contribute to eye strain and serious eye issues

Blue light is part of the visible light spectrum – what the human eye can see. 

Vibrating within the 380 to 500 nanometer range, it has the shortest wavelength and highest energy. 

About one-third of all visible light is considered high-energy visible, or ‘blue’, light. 

Sunlight is the most significant source of blue light. Artificial sources of blue light include fluorescent light, compact fluorescent light (CFL) bulbs, LEDs, flat screen LED televisions, computer monitors, smart phones and tablet screens. 

Blue light boosts alertness, helps memory and cognitive function, and elevates mood, and can help regulate the circadian rhythm, the body’s natural wake and sleep cycle.

Blue light boosts alertness, helps memory and cognitive function, and elevates mood.

However, since the eye is not good at blocking blue light, nearly all visible blue light passes through the front of the eye (cornea and lens) and reaches the retina, the cells that convert light for the brain to process into images.

Continued exposure to blue light over time could damage retinal cells and cause vision problems such as age-related macular degeneration. 

It can also contribute to cataracts, eye cancer and growths on the clear covering over the white part of the eye.

Short-wavelength, high-energy blue light scatters more easily than other visible light. 

Because computer screens and digital devices emit a lot of blue light, this unfocused visual ‘noise’ reduces contrast and can contribute to digital eye strain 

Source: UC Davis 

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