Thursday March 15 2012
Heavy bags may not be the only cause of child back pain
One in four children have back problems because of heavy school bags, according to The Daily Telegraph.
The story is based on a Spanish study of over 1,400 schoolchildren. It found that over half the children had backpacks exceeding 10% of their body weight. The study also found that those carrying the heaviest backpacks had a 50% higher risk of back pain than those carrying the lightest, and a 42% higher risk of diagnosed back problems, although this last result was not statistically reliable.
While the weight of schoolbags can be a concern to parents, this particular research has several limitations that make its results questionable. In particular, it did not properly take account of other factors which might contribute to back problems in children, including a sedentary lifestyle and poor muscle tone.
Surveys done in the UK have found that nearly half of all teenagers have had occasional backache from poor posture, carrying overloaded bags and leading a sedentary, unhealthy lifestyle. Children should wear a well-designed backpack and be encouraged to exercise regularly, which will improve their muscle tone.
Where did the story come from?
The study was carried out by researchers from the University of Santiago de Compostela, Spain. The researchers did not indicate whether or not they received external funding.
The study was published in the peer-reviewed medical journal Archives of Disease in Childhood.
The Daily Telegraph’s opening paragraph suggesting bag weight was the source of back pain for one in four children was misleading. The study found that those who carried the heaviest rucksacks had a higher risk of back pain than those who carried the lightest. It did not show that their back pain caused by heavy rucksacks. This back pain could be due to many other factors, involved including a sedentary lifestyle.
As the study authors point out, a sedentary lifestyle and poor muscle tone is possibly the most important factor associated with back pain in children.
What kind of research was this?
This was a cross-sectional study looking at whether backpack weight is associated with back pain and longer-term back disorders in schoolchildren. A cross-sectional analysis looks at factors at a single point in time, and can only provide a ‘snapshot’ of health and lifestyle factors. As it does not follow people up over time, it cannot show that lifestyle factors lead to particular health outcomes.
The authors point out that back pain among schoolchildren is thought to be associated with a sedentary lifestyle and poor muscle tone. However, school backpacks have also been associated with back pain and it is thought they can create back disorders in adult life. Experts advise that schoolchildren should not carry loads exceeding 10% of their bodyweight.
What did the research involve?
The researchers initially recruited 2,135 pupils aged between 12 and 17, drawn from 11 schools in a province in north Western Spain. Of this number, their final analysis included 1,403 (65.7%). It is not clear why so many participants were excluded.
The children were weighed twice: once with the rucksack or backpack they normally carried but without coats and other items likely to add weight, and a second time without their rucksack. Their height was also measured and information was obtained from a questionnaire given to the children’s teachers and parents about their lifestyle, in particular, frequency of sports activities at school, and how long they were sedentary at home.
The researchers also collected data on the presence of any back disorders previously diagnosed by a doctor (such as scoliosis – curvature of the spine) and whether the children had experienced back pain for more than 15 days in the previous year. It appears that the medical information came from parents or from the children, rather than their doctors.
Schoolbag weights were divided into four ranges by weight (quartiles) and the data analysed to investigate any association between the different quartiles and the reported presence of back pain for more than 15 days. A separate analysis was carried out on the association between schoolbag weight and the presence of a diagnosed back condition.
The researchers also compared the characteristics of the children who were excluded from the study and those included in the final analysis, to ensure they minimised any risk of bias. They adjusted their results for gender, age, body mass index (BMI) and sports activities. The question about sports did not look at how much sports children undertook but only whether they performed some type, recorded simply as yes or no.
What were the basic results?
The average age of participants was 14 years. Of the included children, 92.2% used a backpack with two shoulder straps and the average weight of their schoolbag was 7kg.
Further analysis revealed that:
- 61.4% of children had backpacks exceeding 10% of their bodyweight
- 18.1% carried backpacks exceeding 15% of their bodyweight
- 25.9% reported to have had back pain for more than 15 days in the previous year
- the most frequent diagnosed back disorder was scoliosis (70% of conditions reported)
- children carrying school bags in the heaviest quartile had a 50% higher risk of back pain for more than 15 days than those whose bags were in the lowest quartile (odds ratio [OR] 1.50, confidence interval [CI] 95% 1.06 to2.12)
- there was a non-significant association between carrying bags in the heaviest quartile and a higher risk of long-term back conditions (OR 1.42, CI 95% 0.86 to 2.32)
- girls had a higher risk of back pain than boys
How did the researchers interpret the results?
The researchers say carrying heavy backpacks increases the risk of back pain and possibly of back disorders. They point out that the excessive backpacks carried by many children would not be allowed for adults in employment. Parents and schoolchildren should be strongly advised about the risks posed by heavy schoolbags, they add.
This study has several limitations:
- it had a cross-sectional design (that is, it looked at factors at a single point rather than over time) meaning it cannot tell us whether carrying heavy rucksacks resulted in the development of back pain
- it relied on parents or children remembering how often they had experienced back pain over the previous year, and whether they had been diagnosed with a spinal disorder, which introduces the possibility of a reporting error
- it did not take account of other factors which might cause back pain or spinal disorders, including poor physical fitness, poor posture and structural back problems
- although researchers asked how often children were engaged in sedentary activities, they do not seem to have taken account of this as a possible factor associated with back pain
- they did not look at whether children wore their backpack on one shoulder only, which could have contributed to risk of back pain
Also, the absolute differences in risk of back pain between children carrying the heaviest bags and those carrying the lightest was quite small: nearly 30% of those carrying the heaviest bags had back pain compared to 22.8% of those with the lightest bags. Also, the risk of a back disorder associated with the heaviest rucksack was not statistically significant.
That said, the study raises the important issue of back pain among children. Nearly half of all teenagers in the UK have had occasional backache associated with poor posture, carrying overloaded bags and leading an unhealthy lifestyle. Backpacks worn by children should be well-designed, appropriately adjusted and worn over both shoulders to balance out the weight. Heavy satchels and shoulder bags are best avoided.
Building strong back muscles is important too and children should be encouraged to exercise regularly, in line with current activity guidelines for children.