Epilepsy related mortality.

T he recent concept of sudden unexplained death in epilepsy (SUDEP) has made clinicians more aware of epilepsy related deaths. With the publication of the National Sentinel Clinical Audit of Epilepsy Related Death, the general public and the media became concerned at this apparently new phenomenon. The impact of this audit was such that the chief medical officer, Sir Liam Donaldson, vowed ‘‘to develop an action plan to reduce the level of preventable deaths from epilepsy within three months of publication of this report’’. The Independent newspaper lamented the fact that ‘‘inadequate care by the NHS causes up to 500 deaths a year’’. The Guardian health correspondent, in an article with the headline ‘‘NHS failings blamed for deaths among epileptics’’, interpreted the report as saying that ‘‘about 400 people with epilepsy are dying each year because of failures in diagnosis, treatment and monitoring of the disease within the NHS’’. An editorial in The Lancet, timed to coincide with publication of the audit, concluded that ‘‘poor epilepsy management results in a substantial number of potentially avoidable deaths’’. Although the increased interest in patients with epilepsy is welcome, the excited media reaction to the report, at least where it concerns children, is misleading. It should be remembered that the audit was limited by small numbers and incomplete information. Of 81 deaths that occurred in children under the age of 18 years between September 1999 and August 2002 where epilepsy was judged to be the probable cause of death from examination of the death certificate, quality of general practice and hospital based care was investigated in only 22. It is foolhardy to make general statements about the care of children based on such small numbers and the report itself acknowledges that ‘‘an audit of epilepsy related deaths should not be assumed to be representative of the care provided to patients in general’’. In any discussion of epilepsy related mortality in children, three things should be kept in mind. First, epilepsy related deaths, though tragic, are unusual. Second, data from both the UK and USA show that mortality from epilepsy is declining rather than increasing. Third, the majority of epilepsy related deaths occur in patients whose epilepsy is symptomatic of underlying neurological disease. The time trends in epilepsy related mortality are worth examining. In both England and Wales and in the USA, there has been a steep decline in epilepsy related mortality in the paediatric population (see fig 1) since 1950. The sorts of factors that might underlie these trends have been explored in an age-period-cohort analysis. This approach provides a way of dissecting time trends into three components—age effects, period of death effects, and birth cohort effects. Age effects describe how risk of death from disease varies by age. Period of death effects describe how mortality varies over time. They tend to be large when an effective intervention becomes available. The time trends in mortality for Hodgkin’s disease, for example, show a striking period of death effect in the 1960s when successful treatment was first introduced. Birth cohort effects, on the other hand, characterise changes in mortality not by the time of death but by the time of birth. They show how experience of disease varies by generation. When examining age effects it is clear that mortality from epilepsy shows a small peak in early life (see fig 2). It is possible this reflects mortality in those children with severe hypoxic ischaemic encephalopathy, brain malformations, and inherited metabolic disorders. Risk then falls to a minimum around the age of 10 years, rises again in late adolescence and early adulthood, before levelling off throughout most of adult life. There is a late peak in epilepsy related mortality in old age, presumably secondary to cerebrovascular disease. Period of death effects for epilepsy mortality are small (see fig 3). The implication here is that the introduction of new treatments for epilepsy have had little impact on mortality. By contrast, birth cohort effects in epilepsy mortality are large (see fig 4). Among both sexes in England and Wales, mortality declined strikingly in successive birth cohorts born after around 1950. This finding raises the possibility that the incidence of epilepsy is declining—a view supported by data from longitudinal studies such as the National Child Development Study and the MRC National Survey of Health and Development. 8 It is also compatible with ideas that emphasise the importance of early life in the aetiology of epilepsy and in the subsequent risk of epilepsy related death.