Epilepsy and injury mortality in Sweden--the importance of changes in coding practice

We analysed national mortality trends of injuries and poisoning in patients with epilepsy to establish the importance of changes in coding practice. Patients where epilepsy was a syndrome, either as an underlying or contributing cause-of-death at any time of life, throughout Sweden during 1975-1995 were included. All conditions mentioned on each death certificate were examined, and epilepsy and injury diagnoses were separated according to underlying, contributing or multiple cause-of-death. Annual mortality rates, case-fatality rates, and linear regression coefficients were computed. The most common underlying cause-of-death (UCD) was diseases of the circulatory system (34.4%) followed by epilepsy (31.7%). Injury and poisoning were coded as UCDs for 5.8% of the patients. Injury and poisoning as a contributory cause-of-death increased significantly, but not as an underlying cause during the study period. The proportion of each diagnostic group as an underlying cause decreased by 35% for epilepsy and 18% for injury from 1981 and onwards. These changes should be interpreted with caution since changes of coding practice are more likely to be the cause of these apparent changes. The most frequent specific external causes of injury deaths in epileptic patients were falls and drowning. Intracranial fatal injuries in connection with fall accidents predominated, especially among elderly persons. Deaths related to accidental poisoning were caused by the toxic effect of non-medicinal substances. Cause-of-death statistics from different countries must be interpreted with caution when making international comparisons. Both underlying and contributing cause-of-death statistics should be considered in analyses of mortality trends.