Differential evolution of cognitive impairment in nondemented older persons: results from the Kungsholmen Project

This study was a prospective, population-based examination of the evolution of cognitive impairment, no dementia (CIND).

Subjects 75 years old or older living in Stockholm were assessed at baseline and 3 and 6 years later. The severity of CIND was based on age- and education-specific norms on the Mini-Mental State Examination and was classified as mild (N=212), moderate (N=96), or severe (N=57). Mortality, progression to dementia (DSM-III-R), cognitive stability, and cognitive improvement were studied as main outcomes.

Of the individuals with mild CIND, 63 (34%) died, 65 (35%) progressed to dementia, 21 (11%) remained stable, and 46 (25%) improved between baseline and first follow-up. The relative risks of progressing to dementia by first follow-up in the subjects with mild, moderate, and severe CIND were 3.6, 5.4, and 7.0, respectively. The relative risk of death decreased with increasing severity of impairment. Individuals who improved at first follow-up did not have a significantly higher risk of later progressing to dementia than subjects who had never been impaired (relative risk=1.4). The absence of a subjective memory complaint predicted improvement (odds ratio=5.4).

CIND is a heterogeneous condition: similar proportions of subjects progress to dementia, death, and cognitive improvement over 3 years. There is no increased future risk of progressing to dementia in CIND subjects who improve during that period.