Can using dark mode help us sleep better?
Your circadian rhythm helps control our daily schedule for sleep and wakefulness. It has evolved over millennia and is tied to our 24-hour body clock. It responds to external cues such as sunlight and temperature, which help determine if and when we feel energized or exhausted. Our brain upon receiving signals from the environment it activates certain hormones, alters our body temperature, and regulates our metabolism to keep us alert or prepare us for sleep.
Changes in the environment are captured through our eyes and then signals are sent to different cells about when it’s time to be sleepy or awake. Certain neurons (brain cells) in our brain respond to light and dark. Those cells then send more signals to other parts of the brain that activate other functions that make you more tired or alert.
Hormones also play an important role in the circadian rhythm. For example, melatonin and cortisol increase or decrease as part of the circadian rhythm. Melatonin is the hormone associated with sleep; it makes us sleepy and is usually released mostly at night and suppressed during the day. Cortisol, on the other hand, is produced mostly in the morning and is responsible for making us alert and ready to start the day!
Disruptions in the circadian rhythm can have detrimental consequences to our health. For example, it has been associated with weight gain, impulsivity, slower thinking, and other physiological and behavioural changes. Many internal (e.g., health conditions), as well as external factors, can cause disruptions.
Research suggests that one of those factors is artificial light (i.e. light from screens, lamps, etc). Nowadays, we collectively look at more unnatural light than ever before in human history. The average person in the UK spends over 3 hours a day looking at their phone screen. Blue light coming from screens is perceived in a similar way to natural sunlight by our brains. Exposure to artificial light such as blue light suppresses the production of the hormone melatonin, whose job it is to signal to the body that it’s time to shut down and go to sleep. For example, a 2014 study showed that using a blue-light-emitting iPad before bed suppresses melatonin while reading a traditional book does not. Individuals using an iPad started producing melatonin 1.5 hours later than usual the next day and experienced disruption in their sleep cycles.
Dark mode as a solution?
Dark mode is everywhere these days. All the major operating systems — Android, iPhone, Windows, and macOS — now offer dark themes, which default to light text on a black background.
Apple claims that using dark mode helps users focus better on their work. According to Microsoft dark mode can reduce eye strain and improve the battery life of our devices. Google says that using dark mode can be beneficial to users with low vision and individuals with sensory sensitivities. Dark mode is supposed to emit less blue light than traditional light mode. Could using dark mode reduce the effect screens have on our sleep patterns?
That’s what Apple attempted to do with the introduction of ‘Night Shift,’ a mode that effectively applies an orange filter to your screen. By doing that (in theory) we are exposed to a smaller amount of blue light. This ‘Night Shift’ mode can be automatically activated during certain hours of the day when the brain will naturally start to expect the light to be fading as night falls. This feature is not unique to Apple; Samsung Galaxy phones have a similar version, a “Night Mode” darker screen, and a Blue Light filter button.
Twitter has also experimented with a similar concept by introducing a “Dim” and a “lights out” mode that can be enabled at sunset.
Does it work?
Only a few studies have examined the impact of the dark mode on people’s ability to fall asleep.
A 2019 study of Apple’s dark mode settings looked at melatonin production between people who used Night Shift on their iPad before bed and people who used iPad without Night Shift. No difference was found in melatonin productions between users who had Night Shift one and the ones who didn’t. This suggests that Night Shift alone isn’t enough to restore circadian rhythm. Turning down the device’s brightness settings seemed to have a bigger effect.
A more recent study investigated the effect of Apple’s Night Shift by comparing adults’ sleep outcomes associated with smartphone use before bed with Night Shift enabled to two comparison conditions (iPhone use with no Night Shift, no iPhone use). They recruited 167 adults and used commercially available wrist-worn accelerometers to track their sleep outcomes. No significant differences were found between the Night Shift and no Night Shift groups. For individuals who regularly obtained adequate sleep, abstaining from screen use resulted in better quality sleep than did phone use with Night Shift enabled.
A series of studies looking at the effect of Night Shift modes on alertness, sleep, and memory consolidation, also found no significant effects, suggesting that using Night Shift isn’t solving our blue light problem.
Finally, a group of researchers at the University of Manchester in the U.K. published a paper in Current Biology that also questioned the effectiveness of the night more. The study involved exposing mice to lights that were different in hue but equal brightness and assessing their subsequent activity. The results showed that yellow light (similar to the one used in the Night Shift) actually seems to disturb sleep more than blue. They hypothesised that this could be because warm-toned light, tricks the body into thinking it’s daytime, while cooler blue light more closely mimics twilight. Of course, these findings should be interpreted with some caution; they are based on mice, not humans.
It is clear that more research and alternative solutions are needed. Until then, our best bet for getting a good night’s sleep is avoiding screens.