Many new therapies for dementia target a specific pathologic process and must be applied early. Selection of specific therapy is based on the clinical etiologic diagnosis. We sought to determine stability of the clinical etiologic diagnosis over time and to identify factors associated with instability.

We identified 4,141 patients with dementia or mild cognitive impairment who made at least two visits approximately a year apart to a dementia research center, receiving a clinical etiologic diagnosis on each visit. We assessed concordance of etiologic diagnoses across visits, kappa statistics, and transition probabilities among diagnoses.

The primary clinical etiologic diagnosis remained stable for 91% of patients, but with a net shift toward dementia with Lewy bodies and Alzheimer disease. Lower diagnostic stability was significantly associated with older age, nonwhite race, milder disease at presentation, more underlying conditions contributing to cognitive decline, lack of a consistent spouse/partner informant, and being evaluated by different clinicians on different visits. Multi-state Markov modeling generally confirmed these associations.

Clinical etiologic diagnoses were generally stable. However, several readily ascertained characteristics were associated with higher instability. These associations may be useful to clinicians for anticipating when an etiologic diagnosis may be more prone to future change.