Stability of neurocognitive impairment in different subtypes of mild cognitive impairment

There has been increasing interest in delineating different cognitive subtypes of mild cognitive impairment (MCI). It remains unclear, however, the extent to which neuropsychological impairment associated with amnestic, nonamnestic, and amnestic+ subtypes of MCI remains stable over time. In this study, 70 persons meeting the criteria for MCI and 38 cognitively normal elderly subjects received a baseline neuropsychological evaluation and were reevaluated 1 year later. Our results indicated that 84.6% of the persons initially classified as amnestic, 75% of those classified as nonamnestic, and 80% of the persons classified as MCI+ evidenced stable or more pronounced neuropsychological impairment across the follow-up period. Less than 7% of the amnestic and amnestic+ cases had nonimpaired neuropsychological profiles at their reevaluation at 12 months, and 16.7% of the nonamnestic cases had nonimpaired neuropsychological test profiles at follow-up. Approximately 87% of the cognitively normal subjects at baseline continued to have unimpaired neuropsychological performance at follow-up. These results indicate that the presence of neuropsychological impairment is relatively stable over a 12-month follow-up period among different cognitive subtypes of MCI, although 15-25% of the cases did not exhibit the specific cognitive deficits that characterized their performance at baseline.