Summary
Most people are aware that scrolling through their phone before bed probably isn't great for sleep — but just how much does it actually matter, and for whom? This large 2025 study, published in JAMA Network Open by researchers from the American Cancer Society and the University of Washington, provides some of the most compelling data yet on the real-world impact of pre-bedtime screen use on adult sleep.
Researchers analyzed data from 122,058 adults (median age 56; 80% women) participating in the American Cancer Society Cancer Prevention Study across 35 U.S. states and Puerto Rico. Participants completed a 2018 survey reporting their electronic screen use in the hour before bed, their sleep and wake times, sleep quality, and their natural sleep preference (chronotype — whether they are a natural morning person or a night owl).
What they found:
- Adults who used screens before bed had a 33% higher rate of poor sleep quality compared to those who avoided screens before sleeping.
- Daily screen users went to bed later and accumulated approximately 50 minutes less sleep per week — a meaningful deficit that compounds over time.
- The effects were most pronounced in night owls (people with a later chronotype) — those who already naturally tend toward later bedtimes were hit hardest by pre-bed screen use, creating a compounding cycle of delayed sleep and reduced duration.
- These findings held up even after accounting for other factors that could influence sleep, confirming that screen use itself is independently linked to worse sleep outcomes.
Prior research on screens and sleep has focused heavily on children and teenagers. This study is significant because it confirms that adults are equally affected, and at a very large scale. Sleep deprivation is linked to a wide range of serious health conditions including cardiovascular disease, diabetes, obesity, depression, and impaired immune function. Losing nearly an hour of sleep per week from a single habit before bed is a clinically meaningful finding.
Putting the phone down before bed is not just common sense advice — it is backed by data from over 122,000 people. Pre-bedtime screen use meaningfully shortens sleep, delays bedtime, and worsens sleep quality in adults, with night owls bearing the greatest burden. Simple behavioral changes around screen use could yield significant improvements in sleep health at a population level
PMCID: PMC11950897
PMID: 40146105
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 nonworkdays.
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.