Recent changes to the coding of chest infections in the collection and processing of mortality statistics has contributed to a (virtual, non-veridical) reduction of 2.5% in deaths given the underlying cause of respiratory disease and an increase of 7.0% in deaths allocated to the mental and behavioural disorders chapter, including dementia. Deaths ascribed to an underlying cause of dementia, similarly, increased as a result of a rule change to count aspiration pneumonia as a consequence of one of a number of other conditions. The statistical anomalies resulting from coding changes resulted in a total percentage change of 7.1% in deaths attributed to an underlying cause of dementia.
Impact of the implementation of IRIS software for ICD-10 cause of death coding on mortality statistics, England and Wales. London: Office for National Statistics (ONS), August 8th 2014. Office for National Statistics, Statistical bulletin.