Sharp decline in UK child epilepsy rates

There has been a dramatic fall in the number of children diagnosed with epilepsy over the last decade, according to a new study reported on by BBC News.

The report is based on an impressive piece of research looking at GP records to see whether the rates of children being diagnosed or treated with epilepsy have changed over time.

It found both the number of children with epilepsy by five years of age, and the annual rate of identification of new cases fell over time.

Overall, the number of children born between 2003 and 2005 who were treated for epilepsy by the age of five was a third less than children born around a decade earlier (specifically born between 1994 and 1996).

One theory to explain this drop in cases is that clinicians have got better at diagnosing epilepsy, so less children are being misdiagnosed with the condition.

Another theory is that the introduction of the meningitis C vaccine in 1999 may also be partially responsible – serious brain infections are a significant risk factor for childhood epilepsy.

Whatever the reasons for the change, this well-conducted study suggests the welcome news that the incidence childhood epilepsy in the UK is receding. 

Where did the story come from?

The study was carried out by researchers from University College London, Great Ormond Street Hospital, Young Epilepsy, the University of Edinburgh, and Paddington Green Health Centre. It was funded by the National Institute of Health Research and the Medical Research Council.

The study was published in the peer-reviewed Archives of Disease in Childhood.

This story was well covered by BBC News.

What kind of research was this?

This was a cohort study using data from The Health Improvement Network, a database with a representative sample of approximately 5% of the UK population.

It aimed to examine trends over time in the incidence (number of new cases over a certain period) of epilepsy recorded in the UK among children aged between 0 and 14 years who had been born between 1994 and 2008. The researchers also looked at how trends varied with sociodemographic factors such as age, gender, and social deprivation.

A cohort study is the ideal study design to examine trends in diagnosis rates. However, in this case it cannot tell us why the number of children with epilepsy has fallen.

What did the research involve?

The researchers identified cases of epilepsy recorded in primary care (by local doctors and nurses) among 344,718 children aged 14 years old and under who were born between 1994 and 2008.

Children were followed up until the end of 2008, they transferred to another practice, or they died,  resulting in 1,447,760 years of follow-up in total (4.3 years per child on average).

The researchers identified cases of epilepsy based on treatment, clinical diagnosis or symptomatic presentations recorded in primary care medical records.

The researchers also examined a ‘subcohort’ of this cohort: children aged seven years and under between 2001 and 2008.

What were the basic results?

Over the whole course of the study, 0.38% of children had epilepsy by five years of age based on repeat prescriptions for anti-epilepsy drugs.

If children who had been diagnosed clinically or who had experienced symptoms of epilepsy were also included, 0.68% of children had epilepsy. This is because not every child with symptoms of epilepsy such as non-febrile seizures is diagnosed with epilepsy, and not every child diagnosed with epilepsy is automatically treated with anti-epilepsy drugs, such treatment decisions are made on a case-by-case basis.

The number of children with epilepsy by the age of five declined over time: 1% of children born between 1994 and 1996 had had a repeat prescription for anti-epilepsy drugs, had been diagnosed clinically, or had had symptoms of epilepsy by five years of age. However, the figure dropped to 0.53% for children born between 2003 and 2005, a decline of 47%. This decline was 33% over the same period, if only in children with repeat prescriptions for anti-epilepsy drugs were considered. 

In children aged up to seven years between 2001 and 2008, there were between 71 and 116 cases of epilepsy per 100,000 person years at-risk. However, this figure depends on how epilepsy was defined, it was:

• 71 per 100,000 person years at-risk if epilepsy was defined as having repeat prescriptions for anti-epilepsy drugs, and
• 116 per 100,000 if being diagnosed clinically or having symptoms of epilepsy were also included

In other words, if 100,000 children aged up to seven were followed for one year, between 71 and 116 cases of epilepsy would be expected. The rate of diagnoses was higher in babies aged less than one year than in children aged between one and seven. Rates of epilepsy diagnoses were also higher in boys, and in children from more deprived backgrounds, although the relationship between deprivation and the rate of new diagnoses of epilepsy was not linear.

The number of new cases of epilepsy declined over time. After adjusting for age, gender and deprivation, the number of repeat prescriptions for anti-epilepsy drugs fell by 4% each year after 2001. In addition, the number of children receiving repeat prescriptions, being diagnosed clinically or having symptoms of epilepsy fell by 9% each year.

How did the researchers interpret the results?

The researchers conclude that, “the decline since the mid-1990s in epilepsy recorded in primary care may be due to more specific diagnosis, cessation of treatment for some forms of epilepsy, reduced exposure to risk factors or all of these factors”.

Conclusion

This study has found that the number of cases of childhood epilepsy has fallen over time. This was observed when both the number of children with epilepsy by five years of age and the number of children diagnosed with or displaying symptoms of epilepsy per year were considered.

The researchers report that this decline in childhood epilepsy has also been observed in other European countries.

The reasons for this decline are unclear, but may be due to:

• improved diagnostic accuracy
• changes in treatment practices, so that some milder forms of epilepsy are no longer treated and therefore may not have been identified in this study
• changes in environmental exposures; for example, the introduction of the meningitis C vaccine has led to a fall in the rates of infections of the central nervous system (brain and spinal cord)
• there is also reported to have been a decline in the rates of hospital admissions due to traumatic brain injury among children over the past 15 years – another risk factor associated with epilepsy

Overall, as the researchers say, it is unlikely that any single factor could have caused the decline, and it is more likely the case that a combination of factors – environmental factors in addition to changes in drug prescribing practices and more accurate diagnostic techniques – may account for the trend seen.