Screen time and sedentary behaviour in the early years (Part 1): An introduction

Dr Breanne Kunstler (BBiomedSci, BHealthSci, MPhysio, PhD).

I am often asked for my thoughts on the effects of sedentary behaviour, like screen time, on health. I often hear parents worry about the amount of screen time, like TV watch or video game playing, their children get and the effects on their health. They hear from family, friends and the media that screen time is bad for kids and so they feel guilty allowing their children to interact with screens, despite their large and important role in today's society. I thought I'd do some research to see if screen time is really that bad for kids and, if it is, what we (as parents) can feasibly do to reduce it's effects.

This is post 1 of a five-part series on the potential impacts of screen time on children.

What is screen time?

Screen time involves a child interacting or simply watching a screen, other than for video chatting (e.g. Skype), and is a type of sedentary behaviour. Sedentary behaviour is classified as any “waking behaviour characterised by an energy expenditure of ≤1.5 metabolic equivalents while in a sitting, reclining or lying posture”, which can occur in many situations, such as when a child or infant is watching TV, riding in a pram or sitting in a car (Image 1). So, basically, sedentary behaviour involves bumming around and screen time involves bumming around while using one or more screens (e.g. TV, computer, laptop, gaming console, smartphone or tablet).

Image 1: The Energy Expenditure Continuum (credit: SBRN)

How much screen time should kids be participating in?

Very little is the simple answer. Australian guidelines recommend that children should not be restrained for more than 1 hour at a time (e.g. in car seat) and:

1. Infants (birth to 1 year) should not partake in any sedentary activity or screen time; and
2. Toddlers (aged 1-2 years) and pre-schoolers (aged 3-5 years) should spend <1hr/day being sedentary, including screen time. All sedentary and screen time should be interactive (e.g. educational video game with a parent)

Overall, it is recommended that all time spent sedentary, including while using screens, is kept to a minimum. However, it can be argued that there’s little evidence to support these guidelines.

There appears to be a conflict between the World Health Organisation (WHO), who are partly responsible for setting sedentary behaviour and screen time guidelines globally, and doctors about the harmful effects of screen time and the use of this information to inform parents on how much screen time kids should participate in. This conflict exists because of the lack of research available to support the existence of any harms and, therefore, for creating recommendations for the amount of time kids should spend sedentary. How do we know how much sedentary time is harmful if we have so little research on the topic?

The field of sedentary behaviour research is still very young, despite growing exponentially since 1990. So we don't have much research, but also the studies we do have haven’t had the opportunity to run for a long time, meaning lifelong impacts of sedentary behaviour (and screen time, more specifically) on health can’t be determined yet. Furthermore, a lot of the research we do have has been conducted in a way that only allows us to say that there’s a relationship between screen time and health; we can’t say that screen time has actually caused any kind of change in health (which is important when we’re talking about harms being caused by screen time)(Image 2). Finally, it appears that researchers still haven’t decided exactly how to define sedentary behaviour or screen time. This makes it difficult to compare findings between studies as they could be measuring different things! 

Image 2: Despite what you might think about cheese, I doubt it can kill you in your sleep using your bedsheets (credit: medium.com)

Australian kids are pretty sedentary

The majority of Australian kids are exceeding screen time recommendations. Infants and toddlers are averaging 14 hours per week and 2 to 5 year-olds collect a whopping 26 hours per week. These values are much greater than the 1 hour recommended for children 5 years and under. It’s not just Aussie kids who are accumulating those sedentary hours. International research reports 1 to 6 year-olds spend more than half of their time sedentary. Furthermore, children with disabilities (e.g. autism spectrum disorder) have been found to spend even more time on screens compared to their typically developing peers.

Infants and toddlers tend to spend less time sedentary and more time being active as they get older, probably because they are more capable of playing independently and require less supervision. However, despite this, weekly sedentary time still increases as kids transition from being in childcare to starting school and daily patterns change (e.g. spending more time at a desk).

Image 3: Humans have evolved to be...sedentary (credit: reflexspinalhealth.com)

Being outside of the house can help to reduce sedentary time. Children who attend childcare tend to be less sedentary while they are there compared to when they are home, with those attending high quality childcare being more likely to be less sedentary than children attending low quality care. Childcare centres are usually good at discouraging screen time, but many Australian centres aren’t compliant with recommendations to engage with infants on the ground each day and avoid using equipment that restricts movement (e.g. active play in an open space). Going home after childcare or school can mark a time where time spent sedentary increases, suggesting the home environment is more sedentary than the childcare or school environment.

I don't think we, as parents, can do much to prevent our children from interacting with screens, thereby accumulating large amounts of sedentary time. The evolution of new technologies and online socialising makes adoption of screens by our kids inevitable. The use of screens also tends to happen while lying on a couch or resting in some other way, making it so easy to accumulate large amounts of sedentary screen time (Image 4).

Image 4: Tablets are prehistoric. It was only a matter of time before they evolved into what they are today (credit: Pinterest)

One third of Australian pre-schoolers own a tablet or smartphone, with this figure increasing to two thirds once they hit primary school. One in six Australian primary school age kids have a social media account! They’re so much cooler than I was when I was young (Images 5 and 6). Somehow I don't think these numbers will get any smaller any time soon, so we must learn how to live in harmony with our screens. 

Image 5: Me not being cool (credit: My mum)

Image 6: Coolness has apparently changed over the years. Do kids even say 'cool' anymore? (credit: Facebook)

What about physical activity? Introducing the displacement hypothesis

Children are encouraged to participate in regular physical activity or exercise. 

Participating in physical activity can be beneficial for infants’, toddlers’ and pre-schoolers’ body composition (e.g. adiposity), behaviour, motor skill development, attention, and bone and heart health. Being physically active when young can set kids up to be more active as they get older, helping them to establish healthy behaviours early.

The Australian guidelines recommend that babies and children accumulate physical activity across the day in small chunks. Specifically:

1. Infants (birth to 1 year) should partake in daily supervised physical activity, such as 30 minutes of tummy time that includes various skill development tasks (e.g. reaching); and
2. Toddlers (aged 1-2 years) and pre-schoolers (aged 3-5 years) spend ≥3hr/day doing various supervised physical activities (e.g. running around the backyard or in the park).

This post is on sedentary behaviour in kids, not physical activity. But, I felt it was important to introduce physical activity because it has been shown to reduce the size of the relationship between sedentary behaviour and poor health outcomes, meaning active kids (and adults) might not experience as many deleterious effects from the time they spend sedentary. Also, it is often assumed that kids who are on their screens are doing that instead of being physically active, suggesting one behaviour is simply replaced by another (the 'displacement hypothesis').

It is thought that screens can distract children from participating in physical activities or interactive time with a parent. But this assumes that kids are either participating in screen time or physical activity, which we know isn't true (sleep, anyone?). Just like weight loss isn’t as easy as ‘calories in < calories out = weight loss’, avoiding negative outcomes of sedentary behaviour might not be as easy as ‘sedentary time < physical activity time = no poor health outcomes of sedentary time’. A study of 11-15 year-olds from 39 different countries found >2hrs/day of screen time (mainly gaming and TV) was negatively associated with physical activity, suggesting that the more screen time the children participated in, the less physical activity they did, and vice versa. However, this relationship was stronger in some countries than others, suggesting that context is an important consideration in the trade-off between participating in screen time and physical activity. Kids aren't just simply swapping one for the other. So, the displacement hypothesis might be oversimplifying a more complex issue.

Some researchers suggest that the harmful effects of screen time might be reduced if the child also participates in high levels of physical activity during other parts of the day. One review found that the relationships between sedentary time and poor health outcomes are mostly lost when children and adolescents participate in moderate to vigorous intensity physical activity (e.g. skipping) too, so the negative effects of sedentary time are hidden or removed by the positive effects of participating in physical activity. A large study in adults supports this idea, where adults who participated in high amounts of physical activity had almost completely lost any relationship between mortality (death) and high sitting time from watching TV and participating in other sedentary behaviours (e.g. think about the MAMIL [Image 7] who turns up to work in his lycra). So, does this mean you should go for a brisk walk to make up for the time you’ve spent reading this insightful post?

Image 7: The quintessential Australian Middle-Aged Man in Lycra (MAMIL) Mark Beretta (credit: SMH)

Unfortunately, recent research is mixed in it's support for the displacement hypothesis, so we aren’t quite sure if those who are physically active are participating in minimal screen time as a result, and vice versa. We also still aren't sure if we can make up for our sedentary time by adding some more physical activity to our day. Such a shame that things can’t be so simple! As a physical activity researcher, I still encourage you to go for that brisk walk though, in your active wear (Video 1) if you must.

Video 1: Active wear is so versatile! Think of the places you can go and the coffee you can drink (credit: YouTube)

What are we scared of?

Children participating in screen time is often in the media. Recently there was a call in Vermont, USA, to ban phones for people under 21 as they are “just as dangerous as guns” and people under 21 aren’t “developmentally mature enough to safely possess them”, suggesting that they facilitate driving and texting (reasonable) as well as supporting people to use social media for radicalisation (slightly excessive). I think any call to ban phones is just an unrealistic solution for a complex issue or "wicked problem".

Some professionals suggest that the amount of time spent using screens doesn’t matter; it’s what kids are doing on and off the screens that matters. Many say that screen time should be experienced together with a parent, so the content can be discussed and be used as a learning experience. However, 50% of Australian toddlers and pre-schoolers use screens without supervision, so parents and caregivers are unlikely to know exactly what their children are doing and being exposed to when using screens.

Parents can be scared of screen time as it can provide opportunities for cyberbullying (Image 8), especially for teenagers using their screens at bedtime, which has led to the suicides of too many young people in recent years. Australian parents have reported that 19% of their teenagers have experienced online bullying, but this number is probably higher due to under-reporting of bullying by teenagers to their parents. 

Image 8: Screens can be used for evil, which is a large concern for parents (credit: kidshelpline.com.au)

Other common concerns include digital communication and screens facilitating antisocial behaviour, hindering social skills, and increasing the time kids spend sedentary (possibly leading to obesity and poor sleep). Furthermore, social media use can be considered detrimental to adolescent mental health (cyberbullying) and violent video games are thought to lead to adolescents behaving and thinking aggressively.

So, participating in screen time is being touted as a deadly and almost demonic behaviour, but does it really deserve this? In part 2 I will go into more detail and explore what we currently know about the risks associated with excessive screen time. 

Happy reading!