It’s a widely held belief that the blue light emitted from smartphone screens can disrupt our sleep patterns. The sunlight may be our primary source of blue light, but the increasing prevalence of LEDs and screen usage exposes us to artificial blue light in the evenings, leading to problematic smartphone use and addiction. This blue light is known to suppress melatonin, a hormone our bodies naturally produce to facilitate sleep onset. Consequently, it has been assumed that blue light can make it more difficult to fall asleep. However, recent evidence challenges this notion.
Smartphone screens emit relatively small amounts of blue light, and mounting research suggests that claims about its impact on sleep have been exaggerated. A recent review of global studies published in the journal Sleep Medicine Reviews found no evidence that exposure to screen light within an hour before bedtime makes it harder to fall asleep.
According to Stuart Peirson, a professor of circadian neuroscience at Oxford University, the evidence linking mobile phone use near bedtime to disruptions in sleep and circadian rhythms is not compelling. While the commonly cited 2014 Harvard study, which sparked concerns about blue light from screens, found that mobile phone use before bed delayed sleep onset by an average of 10 minutes, this modest increase in sleep latency should not be a major cause for concern.
However, a closer examination of the Harvard study reveals that participants were asked to read on an iPad at maximum screen brightness for four hours before bedtime—a scenario that does not reflect typical smartphone usage patterns. Peirson emphasises that sleep and circadian responses to light are dependent on intensity, with brighter light eliciting stronger responses.
Although screens are becoming increasingly brighter, they are still relatively dim compared to sunlight and even LED bulbs. Interestingly, the evidence suggests that electrical lighting at home may pose a greater risk for melatonin suppression than mobile phone screens.
Some may argue that screens pose a higher risk because we stare directly at them for extended periods, but modern smartphones are equipped with adaptive brightness features that reduce glare in low-light environments. Moreover, most users do not keep their screen brightness at maximum levels consistently.
While the blue light emitted from smartphone screens is unlikely to be bright enough to cause significant sleep issues directly, the way we use these devices can have a detrimental impact on sleep hygiene. The content viewed, such as work emails or anxiety-inducing social media, can contribute to insomnia or sleep deprivation, and affect our sleep cycle, which is determined by our circadian rhythm, the body’s internal clock. Additionally, becoming too engrossed in interactive activities like video games or dealing with stress during conversations can make it easier to stay up later than intended, thus leading to excessive daytime sleepiness and a decrease in productivity and energy.
Sleep disruptions intensify when individuals keep their phones within reach and allow notifications to disturb them throughout the night. Furthermore, the tendency to stare intently at screens while blinking less frequently can lead to eye strain, dryness, and related issues. To mitigate these effects, experts recommend following the “20-20-20 rule”: Every 20 minutes, look at an object at least 20 feet away for at least 20 seconds.
The efficacy of blue light-blocking products like glasses, filters, and software modes remains debatable. While some studies suggest potential benefits for specific groups, authoritative reviews and organisations have found no clinically meaningful evidence supporting their use. Factors like inconsistent light exposure measurement and poorly understood wavelength blocking capabilities have contributed to the lack of consensus. With conflicting findings and no clear recommendations from experts, determining the appropriate approach to reducing potential blue light effects from mobile phone screens remains a challenge.
If you’re concerned about getting a good night’s sleep, it’s crucial to establish a bedtime routine. Cognitive Behavioural Therapy for Insomnia (CBT-I) is an evidence-based intervention that combines techniques such as:
Furthermore, getting plenty of natural light during the day can help regulate your body clock and reduce sensitivity to light at night.
Blue light has the potential to harm, but it can also be beneficial. One study found that exposure to artificial blue light in the morning increased alertness, positive mood, productivity, energy, and visual comfort in students.
Ultimately, balance is key. Avoid bright light before bed, but don’t worry excessively about the blue light emitted from dimmed smartphone screens or TVs. Taking a break from screens at night, especially for children, and engaging in relaxing activities like listening to podcasts or audiobooks can promote better sleep hygiene.
Make it a habit to establish a calming pre-bed ritual, optimise your sleep environment, limit screen time before bed, embrace a digital detox every now and then, and maintain a consistent sleep schedule.
