Adults who use cellphones or tablets right before going to bed at night are likely to experience poor sleep, according to recent research, which challenges the theory that screen-related sleep disruption primarily affects younger people.
For the study, published in JAMA Network Open, researchers from the American Cancer Society analysed data from more than 122 000 participants in the US and Puerto Rico, focusing on sleep habits and screen use (excluding television) during the hour before sleep.
The study found 41% of participants used screens daily before bed, while 17% reported no screen time at all in that time.
The findings revealed a significant correlation between pre-sleep screen use and reduced sleep quality, reports The Independent. Individuals who reported daily screen use were 33% more likely to report poor sleep quality than those who avoided screens before bed.
Additionally, daily screen users tended to have later bedtimes.
The study also noted that 58% of participants were identified as “morning larks”, individuals naturally inclined to be more active earlier in the day.
Overall, people who used screens before bed each day had 48 minutes less sleep every week.
The light from the screens may play a part, the authors suggested. “Light exposure at night can disrupt sleep by disrupting this natural cycle through delaying the onset of melatonin,” they wrote.
“This can lead to reduced sleepiness and increased alertness.”
But they said that sleep disruptions due to screen use “may not be limited to effects of screen light”, adding: “It is not only the light being emitted from these devices that needs to be considered, but the content as well.”
They said social media was one of the major sources of content being consumed on mobile devices but “only a handful of studies have looked at social media use at bedtime”.
Associations between screen time and poor sleep appeared to be more pronounced among night owls – or people categorised as evening chronotypes, who are more active later in the day.
The researchers said night owls are already at risk of poor sleep due to “social jetlag” or the “misalignment between circadian rhythms and social commitments”, meaning that night owls would prefer to sleep in later but cannot because of work or school.
The team found that morning larks who used a screen before bed went to bed 9.33 minutes later on workdays than those who kept screens out of the bedroom.
And night owls went to bed 15.62 minutes later on workdays. Results were similar for non-workdays.
The authors concluded: “Our findings strengthen the evidence that electronic screen use and disruptions to sleep duration and quality are not limited to children and adolescents but to the broader adult population as well.
“The decrease in quality and duration appeared to be greater among those with a later chronotype and may be due to delayed bedtimes.
“Continued work is needed to understand the mechanisms through which screen use disturbs sleep (e.g, artificial light at night vs content), especially among individuals with later chronotypes who are already at increased risk of poor sleep due to work and social commitments necessitating earlier wake times.”
Study details
Electronic Screen Use and Sleep Duration and Timing in Adults
Charlie Zhong, Matthew Masters, Sidney Donzella et al
Published in JAMA Network Open on 27 March 2025
Abstract
Importance
Electronic screen use before bed may disrupt circadian rhythms, leading to poorer sleep.
Objective
To investigate the association between screen use before bed and sleep outcomes among adults.
Design, Setting, and Participants
This cross-sectional study included participants in the American Cancer Society Cancer Prevention Study–3, a prospective cohort of men and women from 35 US states and Puerto Rico, who responded to a 2018 survey. Analyses were conducted from February 3, 2023, to January 10, 2025.
Exposures
Self-reported electronic screen use in the hour prior to bed.
Main Outcomes and Measures
Self-reported sleep-wake times (used to calculate duration), sleep quality, and chronotype. Mean differences for sleep duration and bedtimes, and prevalence ratios for sleep quality were calculated by screen use using multivariable linear and Poisson regression, respectively. Whether these associations differed by chronotype was also examined.
Results
Of the 122 058 participants (97 658 women [80.0%]; median [IQR] age, 56 [47-62] years; range, 27-85 years), 70 638 (57.9%) reported a morning chronotype. Daily screen use before bed was reported by 50 289 participants (41.2%), whereas 21 275 (17.4%) reported no screen use. Compared with no screen use, daily screen use prior to bed was associated with a 33% higher prevalence of poor sleep quality (prevalence ratio, 1.33; 95% CI, 1.27-1.39) and 7.64 fewer minutes of sleep on workdays (95% CI, 6.65-8.63 minutes). The association was more pronounced among participants with evening chronotypes (8.36 minutes; 95% CI, 4.94-11.78 minutes) vs those with morning chronotypes (5.64 minutes; 95% CI, 3.98-7.29 minutes). Daily screen use was associated with 5.04 fewer minutes of sleep (95% CI, 4.03-6.05 minutes) on nonworkdays. Daily screen users with morning chronotype went to bed 9.33 minutes later (95% CI, 7.61-11.06 minutes), and those with evening chronotypes went to bed 15.62 minutes later (95% CI, 11.93-19.31 minutes) on workdays. Results were similar for non-workdays.
Conclusions and Relevance
Daily screen use was associated with later bedtimes and approximately 50 minutes less sleep each week. Associations were greater among those with evening chronotypes, who are at risk for poor sleep due to social jetlag (ie, misalignment between circadian rhythms and social commitments). These findings confirm disruptions to sleep from electronic screens are not limited to children and adolescents. Further work is needed to understand the best mechanisms for intervention.
JAMA article – Electronic Screen Use and Sleep Duration and Timing in Adults (Open access)
The Independent article – Struggling to sleep? Your phone is likely to blame (Open access)
See more from MedicalBrief archives:
Screens in bed worse for sleep – New Zealand study
Tinted glasses may help the tech-obsessed get better sleep
Regular sleep patterns as important as sufficient sleep
Estimated 1 in 4 children and young people have problematic smartphone usage