The Role of Dementia as Cause of Death: Certifiers' Opinions versus Automated Coding.

Background: Dementia is a major cause of death in many countries today. The way in which countries code causes of death determines the occurrence of dementia in statistics. The change over from manual to automated coding is accompanied by a 7-19% increase in the occurrence of dementia as the underlying cause of death. Because of this sudden change, researchers, physicians, policy makers, and press question the validity of the outcome of automated coding. Therefore, the role of dementia as a cause of death was investigated.

Methods: A questionnaire was sent to a random sample of 700 certifiers who mentioned "dementia" on a death certificate in the second half of 2017. They were asked questions about the role of dementia as a cause of death. For each certificate, the opinion of the certifier was compared with the outcome of automated coding.

Results: A response of 65% (n = 446) was obtained. The automated coding system selected dementia as the underlying cause of death 9.5% points (95% CI: 5.8-14.4%) more often than the certifier would do. This finding in the sample corresponded to an overestimation of dementia in the cause-of-death statistics with 22.7% (95% CI: 18-28%). Main reason for this overestimation was the selection of dementia as the underlying cause of death by the automated coding system, while it was noted as the contributory cause of death on part 2 of the death certificate by the certifier.

Conclusion: For international comparisons of data on dementia as a cause of death, the outcome of automated coding can be used as the system adheres to international (ICD-10) guidelines and reduces coding variations in and between countries. However, for interpreting the local (national) impact of dementia as a cause of death, the opinion of the certifier should be taken into account.