Thursday June 21 2012
Young children 'not active enough'. Does TV help or hinder?
Banning television actually makes children less active, The Daily Telegraph has reported. The paper said that watching sport on TV may in fact encourage kids to go outside and play. Although this news may please footy-mad dads who jealously guard the remote, the headline writers deserve a yellow card.
The news story is based an English cohort study of 1,000 children that compared details at birth and activity levels and body measurements around age nine. It looked at which factors in infancy, and at age nine, are associated with the child’s activity levels at age nine. They found that restricted access to television was associated with doing less exercise, although children who spent more time in sports clubs were less sedentary.
The study also found that boys were more physically active than girls and that the season dictated how active or sedentary children were. Overall, it found that physical activity levels among children were low, with most children not reaching the recommended 60 minutes of daily activity. Of the birth factors, only having an older father was associated with increased sedentary behaviour at the age of nine.
The study does not show that banning TV makes children less active, as the Telegraph claimed. Lifestyle and activity were measured at the same time, so the study cannot demonstrate cause and effect or tell us how they are related. It is quite possible that in households where TV was restricted, this was done to encourage an already sedentary child to become more active. In other words, restricting TV could be a result of a child being less physically active in the first place.
This study cannot tell us which factors may affect children’s level of activity, but it makes sense that encouraging children to join out-of-school sports clubs would be a good idea, as well as identifying physical activities that might appeal to girls. It remains debatable whether giving children free rein over the TV will encourage them to get active.
Where did the story come from?
The study was carried out by researchers from Newcastle University and the University of Strathclyde and was funded by the National Prevention Research Initiative. The study was published in the peer-reviewed medical journal PLoS One.
The Telegraph overemphasised the study’s finding of the link between restricted access to TV and lower levels of physical activity, although it did report a researcher’s comment that this could be a chance finding. Both the Telegraph and the BBC reported comments from researchers that watching sport – such as the current UEFA 2012 European Championships – on TV might encourage children to emulate their sporting heroes.
What kind of research was this?
The information came from a cohort study, called the Gateshead Millennium Study, that collected data on 1,029 infants born between 1999 and 2000. Information on birth factors and social demographics was collected at birth, and data on breastfeeding collected during infancy. This study used the data from the most recent follow-up of the children when they were aged between eight and 10 years.
The researchers say that since early growth is associated with the risk of chronic disease in later life, it is possible that physical activity during childhood may help to prevent such disease. They note that other studies have found conflicting evidence on whether a child’s birthweight is associated with their later activity levels. Therefore, they looked at both birthweight and other lifestyle factors to see how these might influence physical activity levels in children.
The difficulty with this study is that, although this was a cohort, most of the assessments were cross-sectional, made when the child was around nine years of age. It could tell us whether factors measured at birth were associated with physical activity at age nine. However, this study assessed all lifestyle behaviours, sedentary and physical activity, and body mass index (BMI) when the child was aged nine. And because all these assessments were cross-sectional, this cannot demonstrate cause and effect or tell us how they are related.
What did the research involve?
The Gateshead Millennium Study originally recruited 1,029 infants and their families shortly after birth between 1999 and 2000 in the urban district of Gateshead. Information was recorded about:
- parents’ ages
- birth order
- mother’s education
- socioeconomic status
Other information was collected during early childhood, but the research paper provides no further information on any assessments made before the children were between eight and 10 years old.
The present study focused on the follow-up when the children were aged between eight and 10. Researchers measured the height and weight of children to calculate their BMI. Parents were asked about their child’s home environment, including:
- restriction and supervision of TV watching and game playing
- parents’ own TV viewing
- number of TV sets in the household
Children completed a questionnaire, with the help of a researcher, about their participation in school and out-of-school sports clubs.
Researchers used an electronic ‘accelerometer’ (a motion detector similar to that found in smartphones) to measure the children’s physical activity. The devices were given out to 592 children. Parents were asked, for one week, to put the accelerometer on a waist belt on their child when they woke up and to remove it before the child went to bed. The device measured the child’s total volume of physical activity, their moderate to vigorous intensity physical activity and their sedentary behaviour.
Based on this, researchers quantified the child’s average volumes of physical activity, moderate to vigorous intensity physical activity and the average proportion of time spent sedentary. The season during which this assessment took place was also noted. Records that consisted of at least three days were included, although days of less than six hours were excluded.
The researchers then analysed the associations between the child’s levels of physical activity, moderate to vigorous intensity physical activity, sedentary behaviour and the other data they had collected.
What were the basic results?
Of the 592 accelerometers that were given out, 482 were judged to have been worn and measured correctly.
The researchers found significant associations between the levels of total physical activity, moderate to vigorous intensity activity, sedentary behaviour, and:
- the child’s gender – boys were more physically active and less sedentary than girls
- the season when activity was measured – children were less active in winter
The study also found that:
- children of older fathers (as recorded at birth) spent more time in sedentary behaviour (but not moderate to vigorous intensity physical activity or total physical activity)
- children who spent more time in out-of-school sports clubs had reduced levels of sedentary behaviour
- children whose access to TV was restricted had lower levels of moderate to vigorous intensity physical activity
- increased BMI was associated with more sedentary behaviour and reduced levels of moderate to vigorous intensity physical activity
- there was no association between birthweight and physical activity
How did the researchers interpret the results?
The researchers say that a range of factors appears to influence how active or sedentary children were at age nine. Exploring the gender differences in physical activity would be useful they suggest, as would encouraging children to join out-of-school sports clubs.
Encouraging children to be physically active is an important concern for both parents and professionals because lack of exercise is a risk factor for health conditions in later life, such as obesity, diabetes and heart disease. Although this study is of interest and topical importance, it cannot tell us which factors may affect children’s level of activity.
The study was the follow-up of a birth cohort, but assessments of physical activity, sedentary activity, BMI and lifestyle behaviours such as TV watching were all made at age nine. This kind of cross-sectional analysis cannot demonstrate cause and effect or tell us how these factors are related. It is quite possible that TV was restricted in some homes to encourage an already sedentary child to be more active. In other words, restricting TV could be a result of a child being less physically active in the first place. Likewise, it is not clear whether a higher BMI discourages children from doing activity, or whether less activity causes a higher BMI.
The study could tell us more reliably whether there was any association between birth factors and physical activity at age nine. However, this study found no association between birthweight and physical activity. The only association found was that children of older fathers spent more time in sedentary behaviour.
Though the study cannot demonstrate causality, it has some strengths. It objectively attempted to measure the children’s levels of physical activity using an accelerometer, rather than relying on children and parents self-reporting. However, the children’s activity levels were measured for only one week and sometimes less (minimum of three days), so whether such a short time was representative of children’s general activity levels is debatable. There is no way of knowing whether the devices were used correctly, although researchers took steps to ensure they were.
The aim of this study was not specific. The researchers described that they aimed to look at ‘potentially modifiable factors that may influence physical activity in children given its [physical activity’s] association with childhood and later adiposity’. However, it is unclear how the researchers decided on which birth-related or lifestyle factors they chose to assess, or why. For example, they looked at the amount of television watched by both children and parents, but did not examine parental activity levels, which is thought to be a factor in how much exercise children do. There are many factors that may influence children’s activity levels and a study that aimed to examine one in particular might have more reliability.
Overall, this study tells us very little about the factors that influence children’s levels of physical activity. Nevertheless, some of the study’s findings – such as girls being found to be less active than boys – are of concern. It makes sense that encouraging children to join out-of-school sports clubs would be a good idea, also identifying physical activities that might appeal to girls. Whether allowing children free rein over the TV will encourage them to get active is debatable.