Wednesday August 13 2008
Children were tested on their ability to copy a simple design
“Awkward youngsters are more likely to shun exercise and team sports which could lead to their long-term weight gain”, The Daily Telegraph reports. It says that researchers examined the results of 11,000 children who had been tested for “poor hand control, coordination and clumsiness”, and compared the results to their BMI at age 33. The study found that clumsy children were twice as likely to become obese as their coordinated classmates.
Although this study did find some increased risk of adult obesity in those who had ‘poor hand control, coordination and clumsiness’ in childhood, the reason for these observations is unclear (for example whether poorer coordination makes you less likely to participate in sport and so become overweight). There are some limitations to the research, mainly due to methods of assessing clumsiness and coordination, and a great many risk factors for obesity that were not explored. It is not possible to conclude from this study that children with poor coordination will grow up to become obese adults.
Where did the story come from?
Research fellow Walter Osika and Professor Scott Montgomery of Örebro University Hospital, Sweden, carried out the research. The study was funded by the Economic and Social Research Council. The study was published in the peer-reviewed publication: British Medical Journal.
What kind of scientific study was this?
This was a cohort study designed to investigate whether markers of physical control and coordination in childhood are associated with obesity in adulthood. This study used participants from the national child development study, which is following everyone born during one week (3-9 March) in 1958 and living in Great Britain. There were originally 17,000 people in this group, but a number have been lost to the study through death, emigration and a variety of other reasons.
For this study, 11,042 people were available at the age of 33 to have their weight and height assessed to give a BMI measurement. Of these, 7,990 had been assessed by their teachers when they were age seven, for “poor ability in coordination, hand control and overall clumsiness”. The teachers classified children using the responses ‘no’, ‘unsure’, ‘somewhat’ or ‘certainly’. The children’s behaviour was also recorded using the Bristol Social Adjustment Guide, in which the teacher described the child’s behaviour from 150 items and which identified behavioural problems. Of those children, 6,875 were also assessed at age 11 when medical officers measured their BMI and pubertal development. Three functional tests of the right hand to assess hand control and coordination were also carried out. These tests involved the child copying a design, the number of squares the child could draw on a piece of paper within one minute, and the number of seconds it took the child to pick up 20 matches.
When the statistical analyses were carried out on the relationship between an obese BMI at age 33 (BMI ≥30) and clumsiness at seven and 11 years, the researchers took into account numerous confounding variables. These included those that were assessed at birth, such as socioeconomic status, birth weight, mother’s smoking and mother’s age at birth), obese BMI at the time of clumsiness assessment, and other chronic disease variables in the adult that may effect obesity risk or motor function (including disability or neurological conditions).
What were the results of the study?
The researchers found that having an obese BMI at age 33 was generally associated with being of lower social class at birth. For the assessment of control, coordination and clumsiness at age seven, those who had been rated as ‘somewhat’ or ‘certainly’ by teachers, were significantly associated with an increased risk of obesity at age 33 when compared to children who had been rated as ‘no’. This was present even when confounding factors were taken into account.
For the three assessments at age 11, after confounding factors were taken into account, a better performance at copying designs and marking squares was associated with a decreased risk of being obese aged 33. A poorer performance at picking up matches was associated with an increased risk of being obese.
What interpretations did the researchers draw from these results?
The researchers concluded that ‘some of the processes associated with poorer neurological function in obese adults have their origins in childhood’. They acknowledge that the study cannot identify possible biological processes that may be involved and that may link poorer childhood coordination with later obesity.
What does the NHS Knowledge Service make of this study?
Although the study did find certain measures of ‘clumsiness’ in childhood were associated with an increased risk of being obese in adulthood, as the researchers rightly say, the reason for these observations is unclear. The study does have some inherent limitations.
- The reliability of the markers that this study used for neurological function must be considered. The teacher’s assessment that a pupil had poor hand control, poor coordination or was clumsy using measures of ‘no’, ‘unsure’, ‘somewhat’ or ‘certainly’ is highly subjective. The observations that a single teacher would have used to come to these conclusions would differ from child to child and could have been influenced by a single observation rather than longer-term observations (for example the teacher remembering an incident where one child had spilt something that had caused significant disruption to the class). Other teachers may have rated the same child differently, and some teachers may have been more critical in their observations than others.
- Likewise whether the three tests used at age 11 (copying a design, number of squares marked on a piece of paper within one minute, and number of seconds that it took to pick up 20 matches) can be assumed to be a good indication of neurological function is uncertain. It is also worth noting that the researchers ‘selected tests that use the right hand as this is the dominant hand for most people’. If left-handed people performed these tests they are likely to give a poorer performance, but this clearly does not mean that they are any more clumsy.
- There are many risk factors for obesity that have not been accounted for in the study, most importantly diet and activity levels.
- Several factors were taken into account in the analyses including the children’s BMI at age seven. BMI in children is not considered to be as reliable a measure as adult BMI as it does not give a clear indication of the amount of adipose (fatty) tissue and therefore taking this into account may not have effectively avoided confounding.
- In this study, there was no assessment of coordination or clumsiness in adulthood in order to see whether being obese was associated with currently being ‘clumsy’.
- A large number of the original cohort were not available for all of the assessments and they may have differed significantly from the people that were included. This could have affected the results.
‘Clumsiness’ is not an easily definable characteristic; many people would consider themselves to be clumsy at times and it is unhelpful and discriminatory to label any child as being clumsy or lacking in coordination. It is not possible to conclude from this study that children with poor coordination will grow up to become obese adults.
Sir Muir Gray adds...
What this study says is that if children are offered only a limited range of activities, only a limited number of children will participate. The solution is obvious.