A new cross-sectional study of more than 120,000 adults has found that daily electronic screen use in the hour before bedtime is associated with significantly poorer sleep quality and shorter sleep duration. Those with evening chronotypes have more pronounced effects.

The research, published in JAMA Network Open, represents one of the largest investigations to date that examined the association between prebedtime screen use and sleep outcomes in adults.

"Daily screen use was associated with later bedtimes and approximately 50 minutes less sleep per week,” wrote Charlie Zhong, PhD, of the Department of Population Science at the American Cancer Society in Georgia, with colleagues. “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)."

Key Findings

Investigators analyzed data from 122,058 participants (median age = 56 years, 80% women) in the Cancer Prevention Study-3 who responded to a 2018 survey. They found that 41.2% of participants reported daily screen use before bed, while 17.4% reported no screen use.

In fully adjusted models, daily screen use before bed was associated with:

• 7.64 fewer minutes of sleep on workdays (95% confidence interval [CI] = 6.65-8.63 minutes)

• 5.04 fewer minutes of sleep on nonworkdays (95% CI = 4.03-6.05 minutes)

• 18.82 minutes later bedtimes on workdays (95% CI = 17.70-19.93 minutes)

• 19.69 minutes later bedtimes on nonworkdays (95% CI = 18.56-20.81 minutes)

• 33% higher prevalence of poor sleep quality (prevalence ratio = 1.33; 95% CI = 1.27-1.39)

Chronotype Differences

The researchers found that a person's chronotype—their natural tendency toward earlier or later sleep timing—significantly influenced how strongly screen use impacted their sleep. Those with evening chronotypes (35.9% of participants) experienced more pronounced effects compared with morning types (57.9% of participants).

On workdays, study participants with evening chronotypes who used screens daily reported:

• Bedtimes 15.62 minutes later (95% CI = 11.93-19.31 minutes)

• 8.36 fewer minutes of sleep (95% CI = 4.94-11.78 minutes)

In comparison, morning chronotypes with daily screen use reported:

• Bedtimes 9.33 minutes later (95% CI = 7.61-11.06 minutes)

• 5.64 fewer minutes of sleep (95% CI = 3.98-7.29 minutes)

"Participants reporting later chronotypes had later bedtimes," the researchers noted. "Compared with participants reporting neither morning nor evening chronotype, those reporting morning chronotype had a bedtime a mean of 34 minutes earlier on workdays and nonworkdays, whereas those with evening chronotypes reported later bedtimes on workdays by 44 minutes and on nonworkdays by 53 minutes."

Implications

The researchers concluded that their findings expand the evidence that electronic screen use and sleep disruptions are not limited to children and adolescents, but extend to the broader adult population as well. They suggest that the interaction between screen use and chronotype may be particularly important for people who are already at risk for poor sleep.

"Those with a later chronotype (35.9% of our population) are at increased risk for poor sleep due to social jetlag. Social jetlag is a term that was coined to describe the desynchrony between preferred sleep schedules and sleep dictated by social schedules," the investigators explained. "Exposure to screens, and the corresponding disruption to sleep patterns, may be further exacerbating these effects."

Electronic device use before bed may be a modifiable factor that contributes to the ongoing decline in sleep duration and quality observed in adult populations.

No competing interests were declared.