Findings from a recent study published in JAMA Network Open assessed the dose-dependent association between digital screen time and the risk of myopia.
Give me some background.
The broad adoption of digital devices over the past decade has introduced new forms of near-work activity—contributing to an accelerating myopia epidemic fueled by environmental factors prevalent in urbanized societies, such as near-vision activities and reduced outdoor time.
However: Research on the link between digital screen time and the risk of myopia has yielded inconsistent results:
- One meta-analysis found that smart device screen time alone was associated with a 26% increase in the odds of myopia, with that number increasing to 77% when in combination with computer use
- Another study found that screen time on computers and televisions was associated with myopia, while smartphone use was not
Further: While the association of digital screen time with myopia has been documented, the dose-response association and safe exposure threshold remain unclear.
Now talk about the study.
In this systematic review and meta-analysis, investigators included 45 studies of 335,524 individuals (mean age 9.3 years) from the following data sources:
- PubMed
- EMBASE
- Cochrane Library databases
- Cumulative Index to Nursing and Allied Health Literature (CINAHL)
- ClinicalTrials.gov
They identified primary research articles investigating the association of exposure to digital screen devices (ex., smartphones, tablets, game consoles, computers, or television) with myopia-related outcomes (i.e., prevalent or incident myopia and the rate of myopia progression).
Main outcome measure: Increased odds of myopia per hour of daily screen time
How did they analyze the dose-response associations?
A random-effects, dose-response meta-analysis (DRMA) was utilized to examine the pattern of the association of screen time with myopia.
Reminder: DRMA allows researchers to analyze the relationship between disease risk and exposure dose to reveal linear and nonlinear associations.
Findings?
The linear DRMA of those 45 studies and 335,524 participants indicated that 1 additional hour of daily screen time was associated with higher odds of myopia (odds ratio [OR] 1.21, 95% confidence interval [CI] 1.13-1.30).
- Meanwhile, the nonlinear DRMA of 34 studies with 314,910 participants also demonstrated higher odds of myopia with increasing screen time—ranging from 1 hour of daily exposure (OR 1.05, 95% CI 1.01-1.09) to 4 hours (OR 1.97, 95% CI 1.56-2.40).
Interestingly: The dose-response curve showed myopia risk increasing significantly between 1-4 hours of daily screen time and then rising more gradually after 4 hours.
Expert opinion?
The research team assessed the odds of myopia associated with screen time independently of other near-vision activities, such as reading or writing.
They added that digital screen use and other near-vision tasks likely collectively contribute to myopia risk—potentially influencing the dose-response trend.
- Meaning: “Caution is warranted when considering the 1-hour daily screen time safety threshold reported here,” the study authors noted.
Limitations?
They included:
- Some of the included studies did not use objective measures to assess myopia
- Long-term fluctuations or temporal variations in digital screen time were not analyzed because most of the primary studies lacked repeated measurements
- Interstudy variability in how covariates (i.e., the different risk factors that influence myopia) were handled
- The overall certainty of evidence at the outcome level was rated as low in their analysis—largely due to high heterogeneity in the data
- The majority of the included studies were cross-sectional, meaning that associations reported could not be used to determine causal relationships
Take home.
These findings suggest that a daily 1-hour increment in digital screen time was associated with 21% higher odds of myopia.
The dose-response pattern exhibited a sigmoidal shape, indicating a potential safety threshold of less than 1 hour per day of exposure, with an increase in odds up to 4 hours.