Childhood Obesity Surveillance Initiative (COSI)

The COSI survey funded by the Health Service Executive (HSE), is a World Health Organization (WHO) led project that is part of a pan-European initiative. It is an ongoing, systematic process of collection, analysis, interpretation and dissemination of descriptive information for monitoring obesity, being identified as a serious public health problem in the WHO European Region and for use in programme planning and evaluation.

The growing problem of obesity in children is not unique to Ireland and in 2005 the WHO had issued recommendations and guidelines for regular collection of data on weight, height, waist and hip circumference in children worldwide. The Department of Health and Children and the HSE have commissioned the NNSC, to carry out this work in the Republic of Ireland. This ties in with recommendations made in the Report of the National Taskforce on Obesity.

Show/hide contentOpenClose All

Obesity in children is an important health problem, accelerating throughout the world and with particularly alarming trends in Europe. It causes a wide range of serious health and social consequences; it elevates mortality rates in adulthood and also increases the likelihood of adult morbidity such as:

  • Dyslipidaemia
  • Hyperinsulinemia
  • Hypertension &
  • Early atherosclerosis

The health consequences of overweight for children during childhood are less clear, but a systematic review shows that childhood obesity is strongly associated with risk factors for:

  • Cardiovascular disease
  • Diabetes
  • Orthopaedic problems &
  • Mental disorders

Moreover, childhood obesity is linked to underachievement in school and to lower self-esteem. Over 60% of children who are overweight before puberty, will be overweight in early adulthood, reducing the average age at which non-communicable diseases become apparent and greatly increasing the burden on health services, which will have to provide treatment during much of their adult life.

In Ireland, The National Children’s Food Survey conducted between 2003 and 2004 reported that the prevalence of obesity in boys ranged from 4.1 to 11.2 % and in girls from 9.3 to 16.3% (percentage variations depended on methods used for the data collection). This represents a two-to-four-fold increase in obesity in children aged 8–12 years since 1990, (once again years of age variations differed upon the definition of obesity utilised).

The childhood obesity surveillance system will be aiming to measure trends in overweight and obesity in children in order to have a correct understanding of the progress of the epidemic but also allowing inter-country comparisons within the WHO European Region. The implementation of a simple, effective and sustainable surveillance system will be important to tackle and monitor the obesity epidemic in children, reduce the incidence of childhood obesity, identify groups at risk and evaluate the impact of obesity preventive interventions.

At baseline, the core objective was to measure in primary-school children aged 7.0-7.9 years weight, height, body mass index (BMI), waist and hip circumferences, and the prevalence of underweight, normal weight, overweight, and obesity.

A cross-sectional design has been applied.

In 2008, children from first class in primary schools were measured. In 2010, this was extended to measuring children from 1st and 3rd class, in 2012-2013, children from 1st, 3rd and 5th class were measured, and in 2015-2016 measurements were taken in children in 1st, 4th and 6th class.  The fifth round will take place during the school year 2018-2019.

The children in first, third and fifth classes were chosen because these classes include children with the exact ages of 7, 9 and 11 years, respectively. Children in fourth and sixth class were included in 2015-2016 to measure children that had participated in previous rounds. Of course, not all children in the target classes were at that exact age, a variable that could not be determined in advance. Therefore, all children in the target classes were measured.

These age groups precede puberty and eliminate possible differences between the countries that could be attributed to variations in the age of puberty. Also, at these ages the identification of obesity is of value to predict the condition in adulthood. Moreover, at these ages the adiposity rebound (onset of the second period of rapid growth in body fat) starts.

The only comprehensive way to ensure access to children is through the school system.  The researchers have extensive experience in this field through work on the Health Behaviour of School-aged Children (HBSC) survey. The schools were identified through the Department of Education and Science school lists. During the first data collection round in 2008, 163 schools consented to take part. These schools were a representative sample of all primary Irish schools taking account of the issue of small schools in the Republic of Ireland. These same 163 schools had been contacted for the data collection rounds that took place in 2010, 2012-2013, 2015-2016, and 2018-2019.

For each data collection round, the school principals were initially sent a letter outlining the demands of the study and asking for permission for their school to take part. If the principal agreed, then the appropriate class group was selected within the school. Each child was given a letter to take home to their parents outlining the study and asking them to give written consent if they agree that their child should participate. If the letter was not signed, or if the parent stated that they don’t wish for their child to participate, the child was not measured. Moreover, on the day of the measurement, verbal consent was also obtained from the child.

Data has been collected, stored and analysed anonymously. No individual or school will be identified. Over the four data collection rounds, data of in total 17,147 examinations are available. So far, two reports have been published nationally and they form part of a wider European database of growth patterns in European children. The first report was published in 2009, the second report in 2014 and the third in 2017.

Check out the following website for more information on the pan-European COSI study.

Back to Top