Tuesday July 24 2012
A study found heart risks normally only expected in older adults
“Two thirds of obese children show early signs of heart disease”, the Daily Telegraph has reported.
The news is based on a study that examined how common risk factors for diseases that can affect the heart and the blood vessels (cardiovascular disease or ‘CVD’) are in severely obese children. There is no internationally agreed consensus on what constitutes severe obesity in children.
The researchers found that a majority of children identified had risk factors for CVD that you would normally only expect to see in older adults, such as:
- over half (56%) had high blood pressure
- around one in seven had high blood glucose levels
Worryingly, researchers found that when specifically looking at those younger than 12 years, 62% already had more than one CVD risk factor.
These types of risk factors do not usually cause any noticeable symptoms in children but they significantly increase the chance of a child developing a serious disease, such as coronary heart disease in later life.
There are still some limitations to this type of study, including the fact that some obese children might not have been referred to, or seen by, a paediatrician, and a lack of internationally recognised criteria for severe obesity in children.
Also, the study did not have a comparison group and so could not compare findings to children in healthy weight ranges. The findings do reinforce the well-known messages that are common to all age groups:
- eat healthy
- exercise regularly
- aim to maintain a healthy weight
Where did the story come from?
The study was carried out by researchers from VU University Medical Centre, Amsterdam, and other institutions in The Netherlands. Sources of funding were not reported. The study was published in the peer-reviewed journal Archives of Disease in Childhood.
The study was reported appropriately by the BBC and Telegraph though arguably the headlines were slightly misleading as the children had a range of risk factors and not just those that might affect the heart.
What kind of research was this?
This was a prospective observational surveillance study aiming to determine cardiovascular risk factors in children and adolescents with severe obesity in The Netherlands. In an observational study, researchers typically simply observe groups of people, without changing their exposures or circumstances.
Results from prospective studies are usually considered as more robust then retrospective studies which either use data that was collected in the past for another purpose, or ask participants to remember what happened to them in the past.
What did the research involve?
Researchers used information collected from 2005 to 2007 from the Dutch Paediatric Surveillance Unit which Dutch paediatricians report specific diseases to each month. Paediatricians were given protocol describing how to diagnose severe obesity. The researchers specifically looked at reported new cases of severe obesity in those aged from 2 to 18 years. Paediatricians were then asked to complete a questionnaire for each severely obese child including information on:
- socio-demographic factors
- cardiovascular risk factors such as blood pressure, fasting blood glucose, and cholesterol
As there were no internationally accepted criteria for defining severe obesity in children, researchers defined severe obesity using gender and age-dependant cut-off points for BMI based on adult BMI cut-off points for severe obesity (considered as 35kg/m2 or above).
The researchers then compared the reported cardiovascular risk factors values at the BMI cut-off points they set. Results were analysed using statistical methods that compared young children (considered as younger than 12 years) to adolescents (considered as older than 12 years). Differences in age groups, sex, socio-demographic characteristics and the co-morbidities (other diseases) of children were also compared.
Body mass index (BMI) is used as a measure to estimate healthy and unhealthy weight ranges. For most adults a healthy BMI is in the range of 18.5 to 24.9.
What were the basic results?
From 2005 to 2007, paediatricians newly reported 500 children as severely obese. Questionnaires were provided by the paediatricians for 363 of these children (a 72.6% response rate). After accounting for misclassification and missing data, 307 children were included in the analysis with the following results:
- Boys younger than 12 years were more often severely obese, compared to boys older than 12 years.
- Girls older than 12 years were more often severely obese, compared to girls younger than 12 years.
- 40% of severely obese children were of Turkish, Moroccan or Surinamese origin.
- Only one child was obese due to a medical cause.
Of the 307 severely obese children, cardiovascular risk factor information was available for 255 children (83%). The findings for these children were:
- At least one cardiovascular risk factor was identified in 67% of children aged 2 to 18 years
- Two risk factors were found in 17% of children, three risk factors in 8% of children and more than three risk factors in 2.5% of children
- High blood pressure (hypertension) was reported in 53% of overall children, and 53% of children younger than 12 years
- Of overall children, high blood glucose was reported in 14%
- 62% of children younger than 12 years had one or more cardiovascular risk factor
How did the researchers interpret the results?
The researchers conclude that a high number of severely obese children have cardiovascular risk factors. They add that internationally accepted criteria for defining severe obesity, as well as guidelines used for early detection and treatments of severe obesity, are urgently needed.
In discussing the study’s findings, Dr Joana Kist-van Holthe from the university where the research took place said: “The prevalence of impaired fasting glucose in [these children] is worrying, considering the increasing prevalence worldwide of type 2 diabetes in children and adolescents”. She added: “the high prevalence of hypertension and abnormal lipids may lead to cardiovascular disease in young adulthood.”
Doireann Maddock from the British Heart Foundation said of the research: “Although it was a small study, the findings leave a bad taste in the mouth”. She went on to add: “this is a problem that can be addressed by stopping young people becoming overweight and obese in the first place”.
Overall, this study provides evidence that cardiovascular risk factors are common in severely obese children aged 2 to 18. Reporting of severe obesity was high among paediatricians in The Netherlands and was recorded accurately (which is a strength of the study). There are still some limitations to this study, some of which the researchers note:
- Diagnosis of ‘severe obesity’ was reported by paediatricians only. It is likely that children not referred to a paediatrician in the general population were missed and it is not clear how those children differ from ones referred.
- This was a relatively small study which can limit the results, as it may not be able to be generalised to other populations, for example, severely obese children not referred to paediatricians.
- Researchers noted there was a lack of internationally accepted criteria for diagnosing severe obesity in children and suggest an urgent need for these criteria to be available.
- No comparison was made with children in the normal weight range of the same age. This would have added to the strength of the results.
- 40% of the children were of Turkish, Moroccan or Surinamese ethnic descent (which for historical reasons make up a large part of the Dutch immigrant communities). So there may be other factors associated with these ethnicities that may ‘skew’ the results.
Considering that the prevalence and severity of obesity is rising, this study provides valuable information about the risks for children with severe obesity. Anyone concerned about their child being severely obese should see their GP.
Analysis by NHS Choices. Follow Behind the Headlines on twitter.