The Nosology of Dementia

Nosology is the classification of disease. The classification of dementia first as a syndrome distinct from other causes of cognitive impairment, and then as one with several causes, continues to evolve. Current trends aim to move the syndromic diagnosis of dementia more towards being based on cognitive test impairment, and less on how low cognitive test scores impact on function, or on the personhood of the individual with low cognitive test scores. Although this can favour early diagnosis, which will be of especial value if progression can be prevented, it is not without the potential for unintended adverse consequences. Such a trend was anticipated and warned against by early modern commentators on dementia. How far the pendulum will swing towards a low threshold for diagnosis and for how long it will stay there, will be of interest.