Media and developing minds header

Digital Media and Developing Bodies

October 17, 2018

Lauren Hale, PhD


Lauren Hale, PhD

Professor of Family, Population, and Preventive Medicine, Stony Brook University; Editor-in-Chief of Sleep Health

Cordelia Carter, MD

Cordelia Carter, MD

Director of the NYU-Langone Health Women’s Sports Center; Program Director for Pediatric Sports Medicine, Department of Orthopaedic Surgery, New York University School of Medicine, Hassenfeld Children’s Hospital 

Monique LeBourgeois, PhD

Monique LeBourgeois, PhD

Associate Professor of Integrative Physiology, Sleep and Development Laboratory, University of Colorado Boulder

Thomas Robinson, MPH, MD

Thomas Robinson, MPH, MD

Director of the Solutions Science Lab, Stanford University; Pediatrician, Lucile Packard Children’s Hospital

Karla Zadnik, PhD, OD

Karla Zadnik, PhD, OD

Dean of the College of Optometry, Glenn A. Fry Professor of Optometry and Physiological Optics, Ohio State University


Dr. Hale: Most of this Congress is focused on questions about the mind and social environment.  In contrast, this panel is concerned with the body. Its members include a pediatrician interested in obesity, a sleep and circadian rhythm scientist, a Dean of Optometry, and an orthopedic surgeon.   Four themes connect their respective concerns. The first is epidemiology. How prevalent are the physical health concerns relating to digital media and developing bodies? The second is causality. What is the evidence that digital media are affecting these areas?  Third, what are the current methodologies (and methodological challenges) being used by each of the disciplines represented on this panel? Finally, what do we recommend, with respect to children and screens, to address obesity, sleep, myopia, and musculoskeletal issues?

Dr. Hale: What is the status of the widely discussed obesity epidemic, and how does that phenomenon relate to screen use?

Dr. Robinson: The obesity epidemic is a global phenomenon affecting both developed and developing countries.  Efforts to curb it have had little effect. US and global obesity rates continue to rise. That’s especially true for adolescents and adults. There are sporadic reports about obesity plateauing or even slightly decreasing in some parts of the United States, especially in young children, but not generally among low income and minority groups.  The current projection is that one in three of three today’s children will develop diabetes, and half of African-American and Latina females. Obesity soon will be the leading cause of cancer globally. It’s already a major cause of the number one killer (heart disease/stroke).

Dr. Hale: What are the trends in sleep health among children and teens?

Dr. LeBourgeois: The trends differ depending on age and culture.  The National Sleep Foundation recommends 11-13 hours of sleep per day for toddlers and preschoolers, 9-11 hours for school-age children, and 8-10 hours for adolescents.  One-third of parents of children in the two younger age groups report that their kids are not sleeping enough. That hasn’t changed in the past two decades. Only about 20% of teens are averaging 8-1/2 hours or more of sleep per school night.  Another 50% are averaging 7-1/2 hours. Approximately one-quarter of teens are averaging 6-1/2 or fewer of sleep per school night. These numbers also have been stable.

The combination of short sleep during the week and longer and later sleep on weekends – “social jet lag” – is a strong risk factor for many chronic illnesses.  This pattern is a large risk factor for depression, anxiety, obesity, diabetes, and more.

Dr. Hale: Despite the relatively stable average nightly sleep data, other evidence (from Jean Twenge) suggests that since 2010, there’s been about a 17% increase in teenagers getting fewer than 7 hours of nightly sleep.  

Dr. LeBourgeois: In addition to the question of average nightly sleep, trouble falling asleep or staying asleep is a health issue, too.  Your sense of the state of youth sleep hygiene also depends on which of these issues is your focus. Studies show that somewhere between 25% and 50% of kids have trouble falling or staying asleep at some point in their lives.  

Dr. Hale: What is the prevalence of myopia in children and adolescents?

Dr. Zadnik: Myopia is near-sightedness.  It tends to develop during the school years and stabilize in the mid-teens.  It’s estimated to occur in about 30% of the US population, but it’s an epidemic in Asian countries.  Some are predicting that up to 50% of the world population will be myopic by 2050. In places without readily available refractive correction, myopia is the number one cause of visual impairment.

Dr. Hale: Are there specific injuries, such as those to the thumb, wrist, neck, and shoulder, that are becoming more prevalent?

Dr. Carter: Some of these health risks are connected.  For example, obese children are more likely to have ankle sprains, MCL injuries, and dental injuries.  There are other obesity-related injuries with which to be concerned, such as slipped capital femoral epiphysis, or osteochondritis to the knee.  Data also suggest an association between sports injuries and insufficient sleep. As for injuries more directly associated with digital media, over 50% of youth report neck and shoulder pain, and 40-50% report hand, wrist, and thumb pain when asked.  Other injuries worth consideration include temporomandibular joint pain, carpal tunnel syndrome, and back pain.

Dr. Hale: What’s the evidence that there is a causal link between digital media and obesity?

Dr. Robinson: The relationship between mobile digital media and obesity hasn’t been studied enough to draw a firm conclusion about the link between them.  Most of what we know comes from older studies on the use of television, video games, VCRs, DVDs, and computers. With that caveat, obesity is one of the most well-documented outcomes of excessive screen time.  The known associations may seem weak due to methodological limitations. Because of the many potential harms of excessive screen time, there are ethical difficulties with doing a randomized controlled trial of increasing children’s screen time in order to measure the effects on their weight.  What we do know is that several randomized controlled trials from 15-20 years ago show that reducing screen time is associated with less weight gain over time. In some of those same studies, interventions to reduce screen time also resulted in less aggression, less consumerism, and higher grades, compared to controls.   So, we haven’t proven that screen time causes obesity, but we have proven that reducing screen time reduces weight gain – that is really what we need to know because it documents a solution.

The evidence of the mechanisms involved isn’t solid, but it’s primarily related to things that screen time changes.  The first is eating habits. People eat more when they’re distracted, and when they’re exposed to advertising. Second, screen time influences the amount and pattern of sleep.  Third, screen time displaces physical activity; however, of these three mechanisms, this is the one for which the evidence is weakest. According to both observational and experimental studies, screen time and physical activity are somewhat independent behaviors.  That may be because kids are getting so little rigorous physical activity to start with. Another factor is that, according to lab studies, sleep changes are associated with increased energy consumption and differences in the types of foods consumed.

Dr. Hale: How does digital media use affect the duration, timing, and quality of sleep?

Dr. LeBourgeois:  We have cross-sectional and longitudinal (that is, epidemiological) studies on this bi-directional relationship.  The effect sizes are small or medium, but we don’t really understand the effects of digital media on sleep (or vice versa).    No studies actually exposed children or adolescents to media and then looked at how their sleep was affected. There are, however, ongoing studies in which behavioral sleep intervention includes removing media.  The effects so far have been positive.

Three primary mechanisms connect sleep and digital media.  The first is time displacement. The second is the psychological or emotional salience of the content.  The third is that blue spectrum light and bright light from electronic devices suppresses melatonin. That can change the timing of a person’s circadian clock and promote sleep problems.

Dr. Hale: How does screen time affect developing eyes?

Dr. Zadnik: Most available evidence shows no association between near viewing and either the onset or progression of myopia.  Being outdoors in childhood is known to prevent the onset of myopia. (Bright, ambient, natural light differs from the light that screens emit.  It causes dopamine release, which inhibits the abnormal eye growth that causes nearsightedness.) In this sense, it may be our propensity for indoor living, rather than screen time per se, that’s the driving factor here.

Dr. Hale:  What is the causal connection between screen time and musculoskeletal issues?

Dr. Carter: It may be that screen time isn’t displacing physical activity because we’re not physically active to start with.  As for injuries and screen time, it’s not the time spent using digital devices that causes injuries.  It’s the physical positions in which we use those devices. The more (and more consistently) you use just one hand, one thumb, or one neck position, the more likely you are to develop a hand, thumb, or neck problem.

Dr. Hale: What programs and policies are needed to address the impact of screen time on obesity?

Dr. Robinson:  Tested screen time reduction interventions for kids exist.  They can be implemented at home, within families, in schools, and in primary care settings.  They just haven’t yet been adapted to take mobile digital media into account.

With respect to policy and regulation, we’ve long known that marketing adversely affects children.  Despite a consensus about that within the scientific and public health communities, there’s been no progress on even voluntary regulation.  Other countries, uninhibited by our First Amendment, have had more freedom to act on this issue.

One way to think of this issue is that there are externalities that need to be managed – publicly borne costs that result from the negative outcomes produced by private enterprises and markets.  Economic tools such as taxes and industry fees exist to manage externalities. (This approach is taken with some kinds of environmental pollution.)

Digital media also can be used to promote physical activity, better nutrition and sleep.  People who work in behavioral science and behavioral change have a role to play in this. They need to apply the specific qualities of digital media to devise more effective interventions.  What’s coming out of Silicon Valley so far is disappointing.

Dr. Hale: In the UK recently, social media companies were banned from sending electronic notifications to children that might wake them.  How can parents and children control how much screen time they and their children get?

Dr. LeBourgeois:  Digital media isn’t going away.  We’ve been saying for years to reduce screen time in the hour or two before bedtime.  That may not be possible. Many high school students are using computers for homework, and they’re staying up late to do that homework.  One alternative is to us apps like F.lux and Night Guard. They extract the blue spectrum light from electronic screens. Their effectiveness (with respect to melatonin suppression and sleep) is still being studied, but the theory is sound.  Having a central charging station for your family can help, too. Keep the phones out of the bedrooms at night, and use alarm clocks (rather than phones) to wake up.

Dr. Hale: What can we do to prevent eye strain and other ocular issues in developing children?

Dr. Zadnik: We don’t have good answers.  One idea circulating is that, for every 20 minutes of screen time, spend 20 seconds looking at something 20 feet away.  There is no evidence to support it. The kids who experience significant eye strain when using their devices usually have eye problems to begin with.  The screen only accentuates those issues.

Dr. Hale: What about recommendations, with respect to parents, children, and policy, from the musculoskeletal perspective?

Dr. Carter: Support your forearms.  Use both thumbs. Don’t sit with your head bent forward.  Vary your position. If your neck or shoulders are the problem, then hold the device higher to keep your neck in a neutral position.  That will increase the strain on your wrists and hands, though, so hold your device lower if those are your problem areas. Also, pay attention when you’re walking.  Don’t allow your digital devices to distract you. That can result in serious musculoskeletal injuries.

Dr. Hale: The same goes for drowsy drivers texting.

Dr. Carter: There are important unanswered questions about the vulnerability of growth plates.  Could repetitive injuries affect growth plates? And is any of this reversible?

Audience Comment: Integrated guidelines have been promulgated in Canada, Australia, and the UK with respect to these physical risks, because of the interactions among the relevant behaviors.  That doesn’t seem to be happening in the US.

Dr. Robinson: The nature of research here contributes to a disciplinary and problem-specific focus.  For purposes of both research and intervention, a broader approach is needed. For example, building an intervention around after-school team sports programs promotes physical activity and also reduces opportunities for snacking and screen time.  Just as multiple problems may arise when screen time displaces other, healthier activities, multiple solutions may arise when those other activities displace screen time.

Audience Comment (Larry Rosen, PhD): The national organizations to which attendees belong must do something about this, because the government isn’t going to.  One possibility is to prevent psychologists and medical professionals from helping companies create business models that attach kids to their devices.  A group of psychologists sent a letter to the American Psychological Association demanding that any behavioral scientist working with tech companies disclose the techniques they’re using to capture children’s attention.

Dr. Robinson: Susan Linn has brought this up before.  We need to talk more about how the business model is driving everything.  It’s the same one used previously by newspapers, radio, and television. Unless we come up with a new business model, or we start to regulate markets, change is unlikely.

Audience Question (Cliff Sussman, MD):  Some patients say that they need to watch their phones, YouTube videos, or whatever in bed in order to sleep.  Could there be a withdrawal or reward deficiency syndrome making them uncomfortable, and could they need stimulation in order to stop that discomfort?

Dr. Carter: We may not be able to change people’s behaviors.  They have their beliefs regarding media use and bedtime routines.  We can, however, change the content and the negative physiological effects.

Audience Question (Lauren Hartstein, PhD): How strong is the optical community’s consensus regarding damage from blue light devices?  Does research support popular accounts of retinal damage and macular degeneration?

Dr. Zadnik: The jury is still out.  It’s a marketing story for makers of blue light blockers.  The research is in progress.

Dr. Hale: Any comments from Harvard’s Dr. Charles Czeisler?

Audience Question (Charles Czeisler, PhD, MD): Melatonin receptor polymorphism is associated with increased risk of obesity and diabetes.  Can we use this information to personalize guidance about when to limit gaming and eating? For example, can we counsel kids with this risk factor not to do those things at night, when they’re releasing melatonin?  It’s particularly important for those children not to eat high glycemic load foods when melatonin is being released.

Dr. LeBourgeois: This is the type of differential susceptibility that Dimitri Christakis is talking about.  Without screening people for this particular risk, a broadly applicable recommendation is appropriate.

Kids and adolescents have clearer lenses and larger pupils than adults.  This makes their eyes more light-sensitive than adults’, and puts them at greater risk for certain injuries.  It’s an example of why we need to take a developmental perspective to these issues.

Session Materials