Tag Archives: Young people

Screen use at seven: overweight at 11. Why it’s time to say no to a TV in the bedroom for children

Since the launch of the Childhood Obesity Strategy in 2016, there has been much attention focused on the so-called ‘Sugar Tax’. The March 2017 Budget saw confirmation that sugary soft drinks would be taxed in an attempt to combat rising levels of obesity. This is an important move that has been met with widespread approval from public health professionals. Still, obesity is hugely complex and there are many other things at play in addition to the sugary drinks and snacks that children may consume. Researchers at UCL have been looking in detail at different factors associated with obesity and, in a recent paper, find that children who have a television in their bedroom have higher BMI and more body fat than those who do not. Lead researcher, Anja Heilmann, explains the research and why saying no to a TV in the bedroom could be another important strategy in combatting childhood obesity.

As our TV screens have got flatter, our children have got fatter. There is no getting away from it! Screen-based activities play a central role in our children’s lives. At a very young age, they have unparalleled access to television screens, computers, game consoles and a host of mobile devices. Among 5 to 11 year-olds, TV is still the most consumed medium, with gaming coming second.

At the same time, childhood obesity is not just a national, but a global health worry. In 2014/15 a third of 11 year-old children in England were overweight and a fifth were obese.

Research has repeatedly reported a link between TV viewing and obesity, but although some has hinted at the idea that a television in a child’s bedroom might exacerbate the problem, the evidence here has been rather contradictory. Other plausible pathways could include eating unhealthy snacks whilst watching TV, exposure to food advertising and insufficient and poor quality sleep.

Using information from the Millennium Cohort Study (MCS), which has followed the lives of more than 18,000 children born around the turn of the century, we had the opportunity to see whether having a TV in their bedroom when they were age 7 was, in any way, linked with a child being overweight when they were 11 years old. In other words, we wanted to get to grips with whether there were implications over a child’s lifetime of their screen use and if so, what those implications were.

Useful information

Using trained interviewers, the MCS collects a wide range of useful information including the independently measured height, weight and body fat of a child. These provided us with a set of obesity-related measurements: weight, Body Mass Index (BMI) and Fat Mass Index (FMI), a powerful set of measures for overweight and obesity.

When the children were age seven, parents were asked if their son or daughter had a TV in their bedroom, how many hours they spent watching TV or DVDs and how much time they spent playing on a computer.

 At age 7, more than half of the 12,556 boys and girls we looked at in our research had a TV in their room and it was these children who were more likely to be overweight when they turned 11 when we compared them with those without a TV. They were also more likely to have higher BMI and FMI. In total, a quarter of the boys and nearly a third of the girls were overweight at age 11 and the links between having a TV in the bedroom and overweight were stronger for the girls.

Another strength of the research is that we controlled for the child’s BMI at age 3 and maternal BMI, that way adjusting for genetic factors, as well as food environment in the family. We also adjusted for family income and mother’s education – both of which are important as overweight/obesity is socially patterned, as is TV use.

Interestingly, there was no link between overweight and the time a child, whether they were a boy or a girl, spent playing on a computer.

Clear link

So, given the size of our sample and the robustness of the methods employed here, we can say with considerable confidence that there is a clear link between having a TV in the bedroom as a young child and being overweight a few years down the line. For girls, this represents a 30 per cent increase in the risk of being overweight at 11 compared with their peers who do not have one. For boys the risk increases by around 20 per cent.

Another interesting point to note is that the size of this risk or effect is about the same as that of other things shown to be linked with obesity, such as not being breastfed and being physically inactive.

Nevertheless, policy makers looking to create and implement strategies to reduce obesity should certainly consider building access to television screens in children’s bedrooms into their thinking. Specific initiatives focused on young girls could also be important.

Meanwhile, for parents who may consider it a good idea for a young child to have their own TV in their bedroom or feel under pressure to provide one, the message is quite clear: resist the idea and you may be doing even more to set your child on a healthier path into their teenage years and beyond.

Longitudinal associations between television in the bedroom and body fatness in a UK cohort study is research by Anja Heilmann, Patrick Rouxel, Emla Fitzsimons, Yvonne Kelly, and Richard Watt and is published in the International Journal of Obesity.

  • Tvs in the bedroom linked to childhood obesity, study finds, The Guardian

A risky problem: what can keep young people away from alcohol and cigarettes?

Smoking and drinking among very young people has been declining in recent years, but it’s not all good news. There is still a lot of public health concern around the numbers of older children who are consuming alcohol and cigarettes, as these are the young people most likely to come to harm as a result of drinking too much. Their risky behaviours are also likely to persist and intensify into adulthood. So what factors might prevent a young person from smoking and drinking in the first place? New research published in BMC Public Health shows that levels of happiness among children and awareness of the risks may be key to success. Lead author on the research, Noriko Cable, explains more. 

According to Public Health England (PHE), alcohol is now the leading risk factor for ill-health, early mortality and disability among those aged 15 to 49 in England. It wants to “prevent and reduce” the harms caused by alcohol. It also has ambitions to create “a tobacco-free generation” by 2025.

The most recent figures from the Survey of Smoking, Drinking and Drug Use Among Young People in England show that around 90,000 children aged between 11 and 15 are regular smokers and 240,000 have drunk alcohol in the past week. These figures are the lowest they have been since the survey began in 1982.

However, recent research published in BMC Public Health by colleagues at UCL, shows that around one in seven 11 year-olds is drinking alcohol and that having peers who consume alcohol makes them four times more likely to drink that their peers who don’t. We also know that smokers start young, two thirds of them before the age of 18.

So we wanted to examine more closely the sorts of things that might drive young people away from cigarettes and alcohol. In this way we hope to arm policy makers, health practitioners and those working directly with or caring for children and young people with information that can help with the development of clear policies and interventions.

Protective role

We focused on three factors thought to play a protective role in preventing young people from starting to smoke and drink. These were: their awareness of the harms, their well-being or happiness and how supportive their networks of friends and family were.

Information came from Understanding Society, a large UK survey, which, in addition to collecting a wide range of social and economic information from everyone in the household aged 16 and over, has a special self-completion questionnaire for 10-15 year olds. Our sample contained 1,729 boys and girls.

We examined answers at two time points (approximately a year apart) to questions about their smoking and drinking. With these two sets of information, we were able to see whether they had started but then stopped smoking or drinking, whether they were persistent users of cigarettes and alcohol, whether they had started between the first and second surveys (initiation) or whether they had not smoked or drunk alcohol at either point.

The children were also asked about how happy they were with different aspects of their lives, including how they were getting on at school, how they felt about their appearance, family and friends and life in general.

On a scale of 1-4, the children were asked to rate how risky they thought different levels of smoking and drinking were. They were also asked how many supportive friends they had; friends they could confide in.

Harm awareness and happiness

Nearly 70 per cent of the study participants described themselves as persistent non-users of alcohol and cigarettes, and around 13 per cent categorized themselves as persistent users. Persistent non-users scored highest on harm awareness and happiness tests compared to the other groups.

About 8 per cent of the study group labelled themselves as ex-users and about 13 per cent had started using alcohol or cigarettes between the first and second time they completed the survey. Young people aged 10 to 12 were more likely to be in the persistent non-use group, whereas participants aged 13 and above were more likely to be in the persistent user and initiation groups.

We were surprised that while, for most young people, knowledge of the potential and actual harms of alcohol and smoking was linked with them never drinking or smoking, for some it seemed to be associated with them starting to drink or smoke. It is possible that positive expectations from drinking alcohol or smoking cigarettes may, in some way, have overridden their awareness of what harm they could do.

The happier the young person was, and more aware of the harms of alcohol and cigarettes, the more likely they were never to drink or smoke. Having supportive friends to confide in did not play a role in preventing adolescents from using alcohol or cigarettes.

Promoting happiness and harms

So it seems that promoting young people’s happiness and well-being and making them aware of the harms of smoking and drinking may be key to keeping them away from alcohol and cigarettes. In terms of possible timings for information and interventions, another takeaway from the study might be that working with children between the ages of 10 and 12, before they start trying cigarettes and alcohol, could be important.

Because the information used in this study is self-reported, we need to interpret the findings with caution, but they do suggest that making adolescents aware of alcohol and smoking related harm can be helpful in preventing them from engaging in risky health behaviors.

Colleagues at the Centre are now getting to grips with the new age 14 data from the Millennium Cohort Study and, in collaboration with Mentor, a charity working on the ground in schools to tackle alcohol and drug abuse, are hoping to develop our growing body of evidence in this area that will help formulate policies and activities to make some of Public Health England’s ambitions around smoking and alcohol a reality.

Further information

What could keep young people away from alcohol and cigarettes? Findings from the UK Household Longitudinal Study is research by Noriko Cable, Maria Francisca Roman Mella and Yvonne Kelly and is published in BMC Public Health.

 

Reducing harm from alcohol consumption

Child of our Time editor Yvonne Kelly has shared her latest research findings on very young drinkers with policy makers, senior health professionals and third sector groups.

Yvonne was  part of a high profile panel presenting research and taking questions from MPs and others with an interest in the creation of a strategy to reduce harm from alcohol consumption.

The event, organised by The All-Party Parliamentary Health Group and CLOSER (the UK Longitudinal Studies Consortium), comes as a recent report from Public Health England stated that among those aged 15 to 49 in England, alcohol is now the leading risk factor for ill-health, early mortality and disability and the fifth leading risk factor for ill health across all age groups.

It has also been acknowledged that the harmful effects of heavy alcohol consumption go well beyond the implications for public health, presenting both serious economic and social challenges: current estimates of the annual cost to society of alcohol consumption range from 1.3% to 2.7% of annual GDP. In addition, around half of all violent incidents involving adults are alcohol-related.

Photo credit: Jes 

You can find more articles about Yvonne’s research on young people and alcohol by typing ‘alcohol’ into our blog Search bar.

Be prepared: the mental health benefits of scouting and guiding

Being a scout or a guide when we are young might be a good experience for us in all sorts of ways, but can those positive effects be long lasting though our lives and if so, how? Research using the 1958 Birth Cohort shows a strong link between being a scout or a guide when young and better mental health later in life. Professor Richard Mitchell from the University of Glasgow talks to the Child of our Time Podcast about the research, what he and colleagues from Edinburgh found and what he thinks it tells us.

Photo credit: One-and-Other Girl Guides UK

Cyberbullying – the long term effects

For all the wonderful opportunities and connectivity that the internet has brought in recent decades, it seems likely that 2016 will be the year that the internet is mostly remembered for trolling and cyberbullying. It’s a growing phenomenon, not least among school-aged children. In 2015/16 the children’s charity Childline reported a 2 year increase of 88 per cent in calls from children about cyberbullying and the Government recently funded an app aimed at helping pupils report incidents. Meanwhile, a team of researchers at Queen Mary University of London has been looking for the first time at how cyberbullying affects the mental health of young people later on in their lives. Dr Amanda Fahy explains more.

There are three Ps which distinguish cyberbullying from what we might think of as more ‘traditional’ face-to-face forms of bullying: permanence, publicity and permeability.

The thinking behind our study was that all these factors may well mean that the mental wounds and scars inflicted on young people who experience this type of bullying, run even deeper. Certainly it has been identified in numerous quarters as a matter of serious public health concern.

Whilst one or two international studies have demonstrated a link between being a cybervictim and signs of depression, there is little evidence in the UK to show who is affected and how over time. Our research looks at young people who are bullied, those doing the bullying and those who are both bullying and being bullied and goes onto examine their mental health one year down the line.

Regeneration study

The research made use of information collected initially from more than 3,000 Year 7 (aged 11-12) students who participated in the Olympic Regeneration in East London (ORiEL) study which was designed to evaluate the impact of the urban regeneration associated with the London 2012 Olympic Games.

When the students in the study moved into Year 8 (Aged 12-13) they were asked some questions about their experiences of cyberbullying in the preceding 12 months. These included how often they had received rude or nasty comments from someone, become the target of rumours spread online or received threatening or aggressive comments.

The same students were asked if and how often they had been a perpetrator of cyberbullying. Had they sent rude or nasty comments to anyone, spread rumours or sent aggressive or threatening messages online?

A year later when the students had entered Year 9 (aged 13-14) students were asked a range of questions about their experiences and feelings from the previous two weeks and this information was used to create scores for signs of depression, social anxiety and poor mental well-being.

Involvement in cyberbullying

More than 40% of the students reported involvement in cyberbullying in the previous 12 months – 13.6% as cybervictims, 8.2% as cyberbullies and 20.4% as cyberbully-victims. Girls were a lot less likely than boys to fall into the latter category.

Around a quarter of all the young people interviewed showed signs of depression and/or social anxiety and here, with girls more likely than boys to report these symptoms and have lower levels of well-being.

Victims of cyberbullying were almost twice as likely as the completely uninvolved youngsters to show signs of depression even after taking a range of background factors into account. The effect stayed strong even after we accounted for them having poor mental health when they joined the study age 11-12.

Those who reported both being bullied and doing the bullying were more than twice as likely as those who were completely uninvolved to be depressed, whilst those who said they had only been involved in bullying were no more or less depressed than their uninvolved peers.

Damaging effects

The findings for social anxiety and lower levels of well-being were similar to the findings for depression, providing us with a clear picture of the damaging psychological impacts of cyberbullying for victims and for those who were both bullied and perpetrators themselves of cyber bullying.

With 4 out of ten children of this age involved in some way with cyberbullying and given that our results showed that even low level experiences of cyberbullying can have harmful effects over time, it is key that all those involved in the care, education and well-being young adolescents have a grasp of the issues involved and the tools to reduce and prevent its occurrence where possible. Our research indicates that boys and young people who are both victims and bullies are important groups to target.

Longitudinal Associations Between Cyberbullying Involvement and Adolescent Mental Health is research by Amanda Fahy, Stephen Stannsfeld, Melanie Smuk, Neil Smith, Steven Cummins and Charlotte Clark. It is published in the Journal of Adolescent Health.

Photo credit: bad-cyberbully, Winning Information

Sugar-coating the childhood obesity problem

Child obesity figures appear to be on the rise again, causing much concern after earlier signs they had levelled off.  The proportion of  10- and 11-year-olds who were obese in 2015-16 was 19.8 percent, up 0.7 percent on the year before. There was a rise of 0.2 percent among four- and five-year-olds. The announcement comes as researchers at the ESRC International Centre for Lifecourse Studies at UCL have been looking in detail at how and when children become overweight. The team has also been asking whether children who are overweight are more likely to go on to smoke and drink alcohol and if their mental health suffers as they become adolescents. Yvonne Kelly explains the research findings, and considers their implications for the Government’s recent strategy for tackling the childhood obesity epidemic.

The Government’s much-awaited and much-debated childhood obesity strategy was published in August. In the end, it was less comprehensive than had been anticipated, less draconian too. It focuses on two things – reducing sugar consumption and increasing physical activity. But will it be effective in reversing this worrying obesity trend among our children?

It’s fair to say we don’t fully understand what things influence whether, when and why a child might become overweight. Research to date has shown three distinct weight pathways for children: a healthy BMI throughout childhood; becoming overweight during childhood and being overweight/obese throughout childhood.

Previous research has also shown that the child’s mother’s weight, smoking in pregnancy, mental health and other social and economic factors have some link to childhood obesity. But the evidence is far from complete and, where a child’s own mental health is concerned, it’s not at all clear which way the association works.

To try to get a clearer picture of all these things, our research looked at the BMI paths of the participants in the Millennium Cohort Study, which has tracked the lives of nearly 20,000 children born between 2000-2002. We used data collected at birth, 9 months, age 3, 5, 7 and 11.

Once we had established who was on which BMI path, we were able to look at what factors were at play in their lives and to see whether a tendency to overweight and obesity was an indication that a child would go on to face mental health difficulties in early adolescence or start smoking and drinking.

Four pathways to obesity

The BMI data for the 17,000 children we were able to look at for our study showed four distinct groups of children. More than 80 per cent of them stayed on an average non-overweight path throughout their childhood – we call it the ‘stable’ path. There was a small group (0.6 percent) of children who were obese at age 3 but were then in the stable group by age 7. We call them the the ‘decreasing’ group. There was a ‘moderate increasing group’ (13.1 percent) where children were not overweight at age 3 but whose BMIs increased throughout childhood into the overweight (but not obese) range. Finally we had a ‘high increasing’ group of children (2.5 percent) who were obese at age 3 and whose BMIs continued to increase.

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Girls were 30 percent more likely to be in the ‘moderate increasing’ group than boys and were half as likely to be on the ‘decreasing’ path. Indian, Pakistani and Black African children were up to two times more likely to be on the ‘moderate increasing’ path whilst Pakistani, Black Caribbean and Black African children were up to three times more likely to belong to the ‘high increasing’ group.

The wealthiest children were least likely to be in the ‘moderate increasing’ BMI group and children of mums who smoked during pregnancy were up to two times as likely to belong to increasing BMI groups. Children with overweight mums were most likely to be on the moderate and high increasing paths.

Children on the moderate and high increasing paths were less likely to have regular family routines – they were more likely to skip breakfast or have non-regular bedtime schedules. Interestingly, however, no strong links emerged with some of the things more readily linked with childhood obesity such as sugary drinks and snacks, watching TV and lack of physical activity such as sports, the main focus of the newly published childhood obesity strategy.

Overweight factors

So it seems quite a large range of factors influence the likelihood of a child becoming overweight or obese over the first decade of their life. On top of this, being overweight or obese would also seem to point to a less happy and fulfilling early adolescence and a tendency to explore risky behaviours like smoking and drinking.

Although our research did not show a clear link with sugary drinks and snacks, there are nevertheless some compelling arguments for reducing the sugar intake of our children. These are not only related to problems of obesity, but to wider issues including the major issue of tooth decay and associated emergency hospital admissions. There is also increasing evidence of the ‘addictive’ nature of sugar with research suggesting that it stimulates a sort of ‘reward path’ in certain centres of the brain meaning that the more we have the more we want. It has been shown that people who reduce their sugar intake tend to crave it less.

Where sugar taxes have been introduced in other countries (Mexico, France, Denmark, South Africa amongst others), the intervention has been shown to help reduce the consumption of sugary drinks. As yet, there is no evidence that it helps reduce BMI and tackle obesity, but it’s argued it will take time for us to see an effect on whole populations.

Disadvantaged families

It is hard to predict how much impact the voluntary rather than mandatory reduction in sugar content of drinks and snacks agreed in the strategy will have. As for the sugar tax that will be introduced in two years’ time, there remain concerns that disadvantaged families more likely to purchase and consume sugary goods than their better off counterparts will be hardest hit. Policy makers will need to think hard about how any negative consequences of this might be counteracted.

Our research shows clearly that when it comes to the likelihood of a child becoming overweight or obese in the first decade of their life, there are many more influences than just sugar. Those influences are at play in families even before our children are born.

Helping pregnant women to stop smoking and maintain a healthy weight, making sure all young children have healthy eating and sleeping routines would seem to be key, together with targeted support for the ethnic and social groups identified as being most at risk.

Further information and resources

BMI development and early adolescent psychosocial well-being: UK Millennium Cohort Study is research by Yvonne Kelly, Praveetha Patalay, Scott Montgomery, and Amanda Sacker. The work, published in Pediatrics, is funded by the Economic and Social Research Council.

Media coverage

Photo credit: Kim Stromstad

Early puberty: a question of background?

New research examining the connections between early puberty in girls and their socioeconomic and ethnic backgrounds is being presented to an international audience of researchers in Germany today.

Early puberty in 11-year-old girls: Millennium Cohort Study findings is work led by Child of our Time editor Yvonne Kelly using information on 5,839 girls from the Millennium Cohort Study.

The findings, presented at the Society for Longitudinal and Life Course Studies 2016 conference in Bamberg indicate clearly that socioeconomic and ethnic disparities are apparent in the UK and are important for all those interested in the short and long term implications for early puberty on women’s health and well being.

Girls growing up – questions of early puberty

The early onset of puberty in girls has been linked with better bone health in older women, but it is also associated with a host of negative outcomes including teenage pregnancy and serious ill health in mid-life. With girls over the last few decades starting their periods earlier and earlier, this is a real cause for concern. A better understanding is needed of who is affected and how if this trend is to be reversed and the long-term health of girls and women is to be secured. Researchers at the ESRC International Centre for Lifecourse Studies at UCL have investigated whether a girl’s socioeconomic background or ethnicity are associated with early puberty and have looked in detail at more commonly supposed links with weight and stress. Yvonne Kelly explains more.

Sexual activity whilst still young, teenage pregnancy, mental health problems, heart disease and breast cancer later in life are just some of the things linked to early puberty in girls. Over the last few decades, girls have started their periods much earlier with the average age falling from puberty has age falling to 12.9 years in 2015.

This research is the first to look over time at whether and how a girl’s social and economic circumstances and her ethnicity might be linked to the early onset of puberty. We suspected that any link that did emerge would, most likely, be explained away by other factors such as being overweight or suffering from stress.

Using information on 5,839 girls from the Millennium Cohort Study, which has been tracking the lives of nearly 20,000 children born at or around the start of the century, it was possible to know, at age 11 whether they had started their period or not.

Details of their birth weight, ethnicity, family income when they were aged 5 and height and weight when they were 7 were also available. This rich information gathered across 11 years of the girls’ lives really enabled us to put together a detailed picture over time of how these factors come together to influence the early onset of puberty.

The girls’ mothers completed questionnaires any social or emotional problems their daughter might be facing, and their own mental health.

Puberty facts and figures

Nearly one in ten of the girls, a total of 550, had started their period at age 11, with girls from the poorest families twice as likely as their most well-off peers to have done so (14.1 per cent v 6.8 per cent). Those from the second poorest group were also nearly twice as likely to have started their period.

Indian, Bangladeshi and Black African girls were most likely to have started their period at age 11, with Indian girls three and a half times more likely than their White counterparts to have done so.

Other factors

On average, girls who were heavier at age 7 and suffered stress in early childhood were more likely to have begun menstruating. Those who had started their periods early also tended to have mothers with higher stress levels, were from single parent families, and tended to have had some social and emotional difficulties themselves.

However, even when we took all these things into account, girls from the poorest and second poorest groups were still one and a half times more likely to have started their periods early.

As far as ethnicity was concerned, income, excess body weight and stress accounted for part or all of the differences in most cases. Interestingly, though with most Indian girls coming from more advantaged backgrounds than their White peers, the likelihood of them having started their period was not explained after we took all the above factors into account.

Lived experiences

Our findings highlight the different lived experiences of ethnic minority groups in the UK: for example Indians are relatively advantaged whereas Pakistanis tend to be materially disadvantaged, Bangladeshis and Black Africans are materially and psychosocially disadvantaged and have a tendency to be overweight compared with the majority ethnic group. They also demonstrate the complex and potentially opposing factors at play for the onset of puberty.

All that considered, we can say with considerable confidence that socioeconomic and ethnic disparities are indeed apparent in the UK. Given the short and long term implications for early puberty on women’s health and well being, improving our understanding of these underlying processes could help identify opportunities for interventions with benefits right across the lifecourse, not just for the girls in our study, but for future generations.

It was also encouraging to note that in the decade or so covered by the data we used, there appears to have been no further decline in the average age that girls begin puberty.

Early puberty in 11-year-old girls: Millennium Cohort Study findings is research by Yvonne Kelly, Afshin Zilanawala, Amanda Sacker, Robert Hiatt andRussell Viner and is published in Archives of Disease in Childhood.

Photo credit: Afla

Young drinkers: using evidence to prevent alcohol abuse

Research by Child of our Time Editor Yvonne Kelly on 11 year-old drinking has caught the eye of Mentor, a charity working to build resilience among young people to prevent alcohol and drug misuse. The charity’s CEO, Michael O’Toole is now looking to collaborate with Yvonne in future research that will take a look a first look at data from the Millennium Cohort Study in the Autumn. In this episode of the Child of our Time podcast, Michael explains what Mentor is doing, why research based evidence is so important to the charity and how he hopes it will help prevent alcohol abuse among young children in the future.

Photo credit: Joseph Choi

 

Alcohol – who is drinking or drunk age 11?

Child of our Time editor, Professor Yvonne Kelly was among a group of experts looking at drinking behaviour across the life course this week. She presented her recent thought-provoking work on 11 year-olds and drinking at a seminar for policy makers and third sector workers on alcohol and health,  organised by the ESRC International Centre for Lifecourse Studies at UCL.

The talk shared findings from her research on 11 year-olds in the Millennium Cohort Study who had ever drunk alcohol or been drunk. It also explored links with a range of family and social factors including other risky behaviours such as smoking and truancy.

Listen to her talk and see her slides.

Drunkenness and heavy drinking among 11 year olds – Findings from the UK Millennium Cohort Study is research by Yvonne Kelly, Annie Britton, Noriko Cable, Amanda Sacker and Richard G. Watt

What influences 11-year-olds to drink? Findings from the Millennium Cohort Study is research by Yvonne Kelly, Alice Goisis, Amanda Sacker, Noriko Cable, Richard G Watt and Annie Britton and is published in BMC Public Health.