Exploring 12-Year trends in childhood obesity prevalence for the Republic of Ireland – a national study using survey data from 2002 and 2014

Introduction

Childhood obesity remains a global public health priority. In the Republic of Ireland there was a sharp increase in the prevalence of overweight and obesity between the mid-20^th century and the start of the 21^st century. During this period, the average weight of 14-year-olds increased by 65% among boys and 48% among girls, with most of the increase occurring between 1970 and 2002¹. This trend has been mirrored in most developed and developing countries over the last 30 years².

A high body mass index (BMI) in childhood is related to adverse outcomes in adult life such as a greater risk of morbidity³, including some cancers⁴ and type 2 diabetes⁵. It is also associated with a greater likelihood of premature death^6,7. In addition, excess weight in childhood is positively related to lower socioeconomic status⁸ and inversely associated with psychological well-being^9–12. While the personal and social costs related to childhood overweight and obesity are incalculable, financial costs should also be considered. A recent study, conducted in 2017, estimated the total lifetime cost of childhood obesity to be €4.6 billion for the Republic of Ireland, with 21% of costs being direct healthcare costs and more than two-thirds (79%) being indirect costs due to absenteeism, premature mortality and lifetime income losses¹³. This research also suggested that a 1% and 5% reduction in population mean childhood BMI would be associated with a €270 million and €1.1 billion reduction in projected lifetime costs attributable to childhood overweight/obesity in Ireland.

Between 2002 and 2014, 14 nationally or regionally representative studies were carried out in Ireland to determine childhood obesity prevalence estimates. In a systematic review of these studies there was some evidence of a plateau in childhood overweight and obesity¹⁴. However, this apparent plateau was based on studies which were heterogeneous in their methods in terms of whether sampling frames were national or regional, in addition to varying response rates¹⁵.

In a large national oral health survey of over 14,000 children conducted in 2002, 26% of boys and girls in primary school in the Republic of Ireland were overweight or obese¹⁶. This survey also found that prevalence estimates did not vary greatly by economic status as defined on the basis of access to a medical card. In the current research, we have replicated the methods of the 2002 oral health survey in a sample of children recruited in 2014. The aim of this research was to estimate the prevalence of overweight and obesity among children in the Republic of Ireland (including variation by economic status), drawing on data from over 5,000 children aged 4–13 years, and to compare findings with results from the 2002 survey.

Methods

Results

The overall response rates for children in the 2002 and 2014 surveys were 68% and 67%, respectively. The prevalence of childhood overweight and obesity for the years 2002 and 2014, according to the IOTF classification, are presented by age and sex in Table 1²⁰. In 2014, among children aged 4–13 years, one-in-five boys (20%) and more than one-in-four girls (27%) were either overweight or obese. One-in-25 boys (4%) and approximately one-in-14 girls (7%) were obese. The prevalence of overweight was also higher in girls (20%) than boys (16%).

Between 2002 and 2014, among children aged 4–13 years, there were statistically significant decreases in the prevalence of overweight from 19% (95% CI: 18.6%–19.9%) to 18% (95% CI: 17.1%–19.2%), of obesity from 6% (95% CI: 6.1%–6.9%) to 5% (95% CI: 4.8%–6.0%) and of overweight and obesity combined from 26% (95% CI: 25.1%–26.5%) to 24% (95% CI: 22.4%–24.7%). Among boys aged 4–13 years, there were significant decreases in both the prevalence of obesity from 6% (95% CI: 5.3%–6.3%) to 4% (95% CI: 3.5%–5.1%) and of overweight and obesity combined from 23% (95% CI: 22.1%–24.1%) to 20% (95% CI: 18.9%–22.0%). Among girls aged 4–13 years, a significant decrease was only seen in the prevalence of overweight and obesity combined from 28% (95% CI: 27.4%–29.5%) to 27% (95% CI: 25.0%–28.4%).

When only 5-year-olds were analysed, there was a statistically significant decrease in the prevalence of overweight from 19% (95% CI: 18.2%–20.4%) to 16% (95% CI: 14.9%–18.1%) and in the prevalence of overweight and obesity combined from 25% (95% CI: 23.7%–26.2%) to 22% (95% CI: 19.9%–23.4%) over the 12 years. Significant decreases were also observed among boys aged 5 years in the prevalence of overweight from 17% (95% CI: 15.3%–18.3%) to 13% (95% CI: 11.2%–15.3%) and in the prevalence of overweight and obesity combined from 22% (95% CI: 19.9%–23.1%) to 17% (95% CI: 15.1%–19.6%). Among 12-year-olds, while overall there were no statistically significant changes in prevalence between 2002 and 2014, among girls there was a significant increase in the prevalence of overweight and obesity combined from 25% (95% CI: 22.9%–27.5%) to 28% (95% CI: 25.1%–31.4%). Among boys aged 12 years, there were significant decreases in the prevalence of obesity from 6% (95% CI: 4.6%–7.2%) to 4% (95% CI: 2.8%–5.5%) and of overweight and obesity combined from 25% (95% CI: 22.9%–27.6%) to 22% (95% CI: 19.4%–25.0%).

In 2002, 23% (n=3,244) of the sample were characterised as economically disadvantaged compared to 35% (n=1,831) in 2014. In the 2002 survey, children who were economically disadvantaged compared to those who were non-economically disadvantaged had only slightly higher rates of obesity (7.6% vs. 6.2%) and of overweight and obesity combined (26.1% vs. 25.7%) (Table 2)²⁰. However, over the 12-year period this gap increased, with higher rates of overweight (20.5% vs. 16.6%) and obesity (7.6% vs. 4.2%) among children who were economically disadvantaged. The prevalence of overweight and obesity combined was 28.0% in 2014 among children who were from economically disadvantaged families compared to 20.9% among children who were non-economically disadvantaged.

Discussion

This paper presents data from two large national studies of Irish children aged 4–13 years who were examined in 2002 and 2014 by trained oral health survey teams, coordinated by the Oral Health Services Research Centre, University College Cork, using standardised methods. In this 12-year period there has been evidence of a slight fall in the overall prevalence of overweight and obesity combined, with a statistically significant decrease of 2% among children aged 4–13 years. It should be noted that some of the differences observed may be due to the age distribution of the sample. The dental survey targeted Junior Infants and 6^th class students, hence the majority of the sample are 5-year-olds and 12-year-olds, with a clustering of ages around these target years. Therefore, we focused on age-specific trends. There was no change in the prevalence of overweight and obesity among 12-year-olds. However, there was a significant decrease of 3% in the prevalence of overweight and obesity among 5 year-olds, which suggests a possible favourable cohort effect.

The findings from this study are consistent with previous evidence suggesting that childhood obesity rates have stabilised in the Republic of Ireland^14,15,21, in addition to some countries in Europe and in Australia, Japan and the USA²²; they may be decreasing in other countries such as Sweden²³, Denmark²⁴ and Switzerland²⁵. However, while there may be a favourable trend overall, the prevalence gap between economically disadvantaged and non-economically disadvantaged children in the Republic of Ireland is cause for concern. It should be noted that the 2002 survey was carried out at time of affluence in Ireland at the height of the Celtic Tiger years, whereas the 2014 study was held against the backdrop of the 2008 recession. Nevertheless, the socioeconomic gap in childhood obesity is also evident in the United Kingdom^26,27, while widening socioeconomic disparities in childhood overweight have been reported in Sweden²⁸ and other countries across Europe²⁹.

The Irish research evidence suggests that socioeconomic inequalities create living conditions that are damaging to health, most particularly for poor and vulnerable members of society. In this context, gathering best evidence on tackling health inequalities and reconfiguring what needs to be done has never been more important³⁰. From a public health perspective, these findings suggest that targeted strategies to reduce the impacts of socioeconomic inequalities are needed. Children attending disadvantaged schools deserve special attention, especially as they approach adolescence, and health promotion policies should target the obesogenic environment they are exposed to³¹. However, there is a lack of evidence of the health inequality impact of existing policies and interventions in the Irish context³⁰.

The Healthy Weight for Ireland Obesity Policy and Action Plan 2016–2025 outlines a 5-year target of reducing the prevalence of overweight and obesity combined amongst children in the Republic of Ireland by 0.5% per annum. It also aims to reduce the gap in obesity levels between the highest and lowest socioeconomic groups by 10%³². If these targets were achieved, we would expect to see a further fall in the prevalence of childhood overweight and obesity from 24% to 21% by 2020. Actions that have been implemented, or which are soon to be realised, include a tax on sugar-sweetened beverages, a formal review of the advertising of energy dense food and drinks to children, the expansion and wide scale implementation of effective school initiatives/interventions on healthy eating and physical activity in schools as well as the introduction of national food standards for primary schools.

The inclusion of obesity prevention and care as part of primary care (including implementation of an appropriate child growth monitoring system) is another important development within Ireland³². As previously noted, to date, childhood obesity prevalence rates in Ireland have been assessed using studies that are heterogeneous in their methods with regard to national or regional sampling frames. Information from general practices could supply an annual source of objectively measured child BMI data that might provide accurate and reliable population-based data for the routine monitoring of childhood overweight and obesity in order to examine patterns and trends. These data could also be used for assessing the efficacy of the obesity prevention health interventions outlined above. Data collected could also include information on utilisation of healthcare services (both primary care and hospital services) and illness-related productivity loss and absenteeism from work and school for conducting cost-of-illness studies and other related health economic analysis¹³. In particular, data from general practices could provide an annual source of BMI/health-related data for children who are under 5 years of age – which has been lacking.

Conclusions

The findings from this research are consistent with stabilisation, and a possible declining trend, in the prevalence of overweight and obesity among Irish children aged 4–13 years between 2002 and 2014. The trend was most marked and statistically significant within the subgroup of five-year-old children, raising the possibility of a favourable birth cohort effect. However, evidence for an increase in social inequality among overweight and obese children is important and should be a key public health policy issue.

Data availability