A recent study may challenge the conventional understanding of screen time and sleep in adolescents.
In the study, published in JAMA Pediatrics, researchers used objective measures to track screen time and sleep patterns in 79 participants over 4 nonconsecutive nights.
The researchers employed a repeated-measures design and within-person analysis to account for night-to-night variability, providing advantages over previous research that relied on aggregated data.
The participants (47 male, 32 female) had a mean (standard deviation [SD]) age of 12.9 (1.1) years. Participants were ethnically diverse: 5 Asian, 30 Māori, 41 New Zealand European, and 3 Pacific. Data were collected from March to December 2021 in Dunedin, New Zealand.
Screen time was measured using compact, high-resolution wearable cameras (PatrolEyes SC-DV7 Ultra) worn on chest harnesses for 2 hours prior to bedtime, while stationary cameras in bedrooms captured screen use after participants got into bed. Video data were coded using a reliable protocol (κ = 0.92) to quantify device types (8 options) and activities (10 options).
Sleep duration and quality were measured using waterproof Axivity accelerometers worn on the nondominant wrist 24 hours a day for 8 days. Sleep variables were obtained using an automated script developed in MATLAB.
Among the key findings were:
- Screen use in the 2 hours before bed had no statistically significant association with total sleep time or most measures of sleep health.
- For every 10 minutes of additional screen time once in bed, total sleep time decreased by 3 minutes (95% confidence interval [CI] = −6 to −1 minute).
- Interactive screen use in bed was associated with a mean difference in total sleep time of −9 minutes (95% CI = −16 to −2 minutes) for every additional 10 minutes of use.
- Gaming while in bed was linked to a reduction in total sleep time of 17 minutes (95% CI = −28 to −7 minutes) for every 10 minutes of gaming.
- Multitasking across multiple devices in bed was associated with a mean difference in total sleep time of −35 minutes (95% CI = −67 to −4 minutes) on nights when this occurred.
The researchers found that screen use in the 2 hours prior to bedtime was not associated with reduced sleep duration or quality in youths aged 11 to 14 years. However, the study revealed that screen use after getting into bed, particularly interactive activities like gaming and multitasking, was associated with shorter sleep duration and delayed sleep onset.
Mean (SD) screen time in the 2 hours before bedtime was 56 (25) minutes, with a night-to-night variability of 27 (11) minutes. The participants spent an average of 16 (26) minutes using screens after getting into bed but before attempting sleep.
Screen use patterns included:
- Mean (SD) passive screen time before bed: 37 (24) minutes
- Mean (SD) interactive screen time before bed: 22 (23) minutes
- Mean (SD) social media use before bed: 5 (8) minutes.
In-bed screen use patterns included:
- Mean (SD) passive screen time in bed: 11 (20) minutes
- Mean (SD) interactive screen time in bed: 3 (6) minutes
- Mean (SD) social media use in bed: 4 (9) minutes.
Sleep patterns observed were:
- Mean (SD) total sleep time: 7.2 (0.9) hours
- Mean (SD) time awake after sleep onset: 55 (41) minutes
- Mean (SD) shut-eye latency: 29 (28) minutes
- Mean (SD) sleep latency: 43 (36) minutes.
Weekday vs weekend patterns showed:
- Mean bedtime on weekdays: 21:21 (57 minutes)
- Mean bedtime on weekends: 21:59 (14 minutes)
- Mean sleep onset on weekdays: 22:32 (49 minutes)
- Mean sleep onset on weekends: 23:12 (14 minutes)
- Mean sleep offset on weekdays: 6:41 (38 minutes)
- Mean sleep offset on weekends: 7:22 (15 minutes).
Screen use in the 2 hours before bed was associated with delayed sleep onset but also corresponded with delayed sleep offset, resulting in no significant change in total sleep time. For instance, on nights with passive screen time, sleep onset was delayed by 32 minutes (95% CI = 11–53 minutes), but sleep offset was also delayed by 27 minutes (95% CI = 7–47 minutes).
In contrast, screen use after getting into bed was associated with reduced total sleep time. Interactive screen use in bed was particularly impactful, with every 10 minutes of use associated with a 10-minute delay in sleep onset (95% CI = 4–16 minutes).
Social media use in bed, while less common, was also associated with significant sleep delays. On nights with social media use in bed, sleep onset was delayed by 38 minutes (95% CI = 15–60 minutes) compared with nights without social media use.
The researchers found no statistically significant associations between screen use and sleep latency or time awake after sleep onset, suggesting that screen time may primarily affect sleep through time displacement rather than direct effects on sleep quality.
Additional analyses revealed:
- Screen use in the 30 minutes before attempting sleep occurred on 61.9% of nights
- Screen use in the 1 hour before attempting sleep occurred on 81.1% of nights
- Screen use in the 2 hours before attempting sleep occurred on 90.7% of nights.
A sensitivity analysis showed that the results were broadly comparable when analyses were restricted to weeknights only, with some greater differences in in-bed use.
To assess potential reactivity, 61 participants (77.2%) reported no change in behavior despite the video recordings.
Limitations of the study included the labor-intensive manual coding of video data, the relatively narrow age range of participants, and the possibility of residual confounding. The researchers acknowledged that while efforts were made to minimize behavioral modifications due to observation, some impact could not be ruled out entirely.
Conflict of interest disclosures can be found in the study.