Background: People who are cognitively impaired not demented (CIND) can be at an increased risk for developing dementia, but little is known about the natural history of CIND in clinical settings.
Method: We examined the 2-year outcome of CIND subjects in the Canadian Cohort Study of Cognitive Impairment and Related Dementias.CIND was diagnosed when at least one positive item was endorsed on the DSM-III-R dementia criteria, but not all criteria were met. CIND was further subclassified as: pre-Alzheimer's disease (pre-AD), vascular cognitive impairment (VCI-ND), non-AD degenerative, psychiatric, other neurologic, other medical conditions, mixed disorders and no etiology identified (not otherwise specified [NOS]).
Result: Of 146 CIND patients with 2-year follow-up data available, 49 (34%) progressed to dementia, while 20 (14%) recovered to not cognitively impaired (NCI). Progressors were significantly older than stable CIND and reverters (p < 0.0001; mean age = 71.1, 64.3, and 59.1, respectively), and there were significantly (p = 0.001) more ApoE epsilon4 carriers among progressors (67%) than stable CIND (29%) and reverters (12%). Pre-AD CIND and VCI-ND had the highest rate of conversion to dementia (41.0 and 40.0%, respectively), while psychiatric CIND and CIND NOS had highest rate of recovery to NCI (20.0 and 30.0%, respectively). All conversions in pre-AD CIND were to 'probable AD'.
Conclusion: CIND consists of a heterogeneous group of disorders that can be classified syndromically. Many subclassess - not just those with pre-AD CIND - are at high risk of progression to dementia, usually to Alzheimer's disease.