Sharp decrease in observed cerebrovascular mortality may be due to certification and coding

Aims and methods: Being easily available and having good coverage and comparability, official mortality statistics are used very widely. This in turn is because the definitions of mortality and methods of pertinent data collection are coordinated worldwide by the World Health Organization. In Estonia, registered cerebrovascular mortality has dropped 50% since 2000. A less dramatic decrease has been observed in nearly all EU Member States. To find out if this development can be explained by changing certification and coding practices, we counted all mentions of cerebrovascular diseases in the Estonian Causes of Death Registry database between 2004 and 2013 and analyzed the selection of the underlying cause of death. Results: We found that the sharp decrease in registered cerebrovascular mortality was by a half due to an increased selection of hypertension as the underlying cause of death. In cases where a cerebrovascular disease was mentioned and selected the underlying cause of death, the mean number of diagnoses per record was 2.45, in cases where a cerebrovascular disease was mentioned, but hypertension selected the underlying cause of death, the mean number of diagnoses was 3.15. Conclusions: The choice of the underlying cause of death registered in official statistics depends on the level of details provided in a death certificate, as well as updates to coding rules and use of modern quality assurance instruments in data production.