Health news - Premature or underweight babies are more at risk of hyperactivity disorder
9 June 2006 - written by Alexander Whitehead for Bupa's health information team
Babies born before they reach full term, or those with low birth weight, are up to three times more likely to become hyperactive and have short attention spans, according to a study published online this month in the Archives of Disease in Childhood.
How was the study carried out?
Danish researchers looked at the birth records of 834 children diagnosed with hyperkinetic disorder (HKD). This is one of the most common mental disorders diagnosed among children and is characterised by hyperactivity, low attention span, and impulsive behaviour. The researchers then compared these birth records with those of around 20,000 children with no mental disorders.
The research team looked closely at the gestational age of each child. This is the time period between the woman's last menstrual period (or her earliest ultrasound measurement) and birth, so it means how many weeks pregnant the woman was when the baby was born. A gestational age of below 37 weeks was classed as 'preterm'; a gestational age of below 34 weeks was classed as 'very preterm'.
The researchers also looked for any links between gestational age, birth weight and HKD.
What did the study show?
Children born below 34 weeks were almost three times more likely to develop HKD than children born after 37 weeks. Children born between 34 and 36 weeks were 80% more likely to develop the disorder.
The study also showed that underweight babies born at full term were at risk of getting the syndrome. Babies born at term weighing between 1500 and 2499g were 90% more likely to develop HKD. Those who weighed between 2500 and 2999g at birth were 50% more likely to develop the condition than those who weighed more than 2999g at birth.
Of the 834 children confirmed as having HKD, 90% were boys. However, the study showed that the increased risk of HKD applied to both boys and girls.
Why does HKD affect children born prematurely and/or with low birth weight?
This is not completely understood. However, the researchers believe that certain receptors in the brain may be damaged in some premature babies, particularly those with a gestational age of less than 34 weeks. There may be a link, they argue, between such damage and the development of HKD.
Were there any other factors than made HKD more likely to develop?
Yes. Babies born into single-parent families were more likely to develop HKD. Parents who were very young themselves, or on low incomes, were more likely to have babies who developed HKD. However, the results of the study still hold true even after these factors have been taken into account.
How conclusive were the findings?
The sample of children used in the study was very large, which lends the results extra weight. Previous studies generally used smaller samples of children and tended to concentrate on the related condition called attention deficit hyperactivity disorder (ADHD) at gestational ages below 28 weeks. The current study claims that the majority of premature births occur at higher gestational ages, and that their findings are consequently more relevant.
The current study also looked at the association between gestational age and birth weight in a more detailed way than previous studies.
What's the difference between HKD and ADHD?
HKD and ADHD are often used to describe the same condition: when children are overactive and have difficulty concentrating. The term ADHD is more commonly used in the US, whereas the official term in the UK is HKD.
HKD is sometimes defined as a more severe type of ADHD. It can be called combined-type ADHD, as appears to be the case in the present study, and is diagnosed when a child has particularly high levels of hyperactivity.
What are the signs of ADHD/HKD?
Signs that children may have ADHD/HKD are listed below. They include children who:
- are restless, fidgety and overactive
- continuously chatter and interrupt people
- are easily distracted and do not finish things
- are inattentive and cannot concentrate on tasks
- are impulsive, suddenly doing things without thinking first
- have difficulty waiting their turn in games, in conversations or in a queue
How can I be sure my child has ADHD/HKD?
There is no physical test for the condition, such as a blood test. Many children have problems with restlessness and inattentiveness without having ADHD/HKD. They may have other problems that result in behaviour that is similar to ADHD/HKD - such as dyslexia, language or hearing difficulties. Other conditions can also mask the condition, such as Asperger's syndrome and obsessive-compulsive disorder (OCD).
How common is ADHD/HKD?
It's thought to affect three to seven per cent of school-age children. Boys are up to three times more likely to be affected than girls. Girls more commonly display symptoms of inattention, whereas boys tend to show more symptoms of hyperactivity. Around 30 to 50% of sufferers continue to have symptoms into adulthood.
More and more children are being diagnosed with ADHD/HKD as awareness of the condition increases.
What causes ADHD/HKD?
Doctors are not exactly certain what causes ADHD/HKD, but it does tend to run in families. Poor parenting or family stress does not appear to be a specific cause. The current study argues that premature birth or low birth weight may be one cause.
How can the risk of pre-term birth or low birth weight be reduced?
Mothers should take care of their health during pregnancy to minimise the risk that they will give birth to a premature or low birth weight baby, although nothing can ensure a perfect birth. It's important to eat a balanced diet and include foods that contain calcium, folate and iron. This is because the baby in the womb is nourished by the mother and may be affected if she eats poorly.
Regular exercise will help to protect the fetus. Babies born to smoking mothers are also more likely to be born with a low birth weight. The Department of Health advises women who are trying to become pregnant or are at any stage of pregnancy, not to drink more than 1 or 2 units of alcohol once or twice a week, and recreational drug use should also be avoided.
When is it usually diagnosed?
ADHD/HKD is usually noticed in early childhood, when a child starts to show disruptive behaviour that is not in keeping with the behaviour of other children of a similar age.
Some case are undiagnosed, or diagnosed later in life. The age at which the children in the present study were diagnosed ranged from 2 to 18 years.
Without diagnosis and proper treatment, ADHD/HKD can have serious consequences. These can include under-performance at school, depression, relationship problems, difficulties with employment and even criminal behaviour.
How is it treated?
Most experts agree that, once diagnosed, a combination of treatments is the best way to manage the condition. These include psychiatric help, individual and family therapy, medication, extra assistance at school, social-skills training, coordination training (for the child), dietary advice and parental support.
Some parents see an improvement in the behaviour of an ADHD/HKD sufferer when changes are made to their diet. For example, reducing intake of caffeine (found in chocolate, coffee and some carbonated drinks), and some artificial colourings have been found to help.
Bupa information
- Bupa factsheet: Attention deficit hyperactivity disorder (ADHD)
- Bupa factsheet: Antenatal care
Sources and further information
- Linnet KM, Wisborg K, Agerbo E, Secher NJ, Thomsen PH, Henriksen TB. Gestational age, birth weight, and the risk of hyperkinetic disorder. Arch Dis Child 2006;000: 1-6. doi. 10.1136/adc.2005.088872
- Department of Health
www.dh.gov.uk - ADDISS
www.addiss.co.uk - BLISS - The premature baby charity
www.bliss.org.uk - Mental Health Foundation
www.mhf.org.uk - Royal College of Psychiatrists
www.rcpsych.ac.uk
