If this failure is due to sample size, larger studies should solve it. However, it. could also be due to heterogeneity; clinicopathological studies seeking pathological markers of both non- AD dementias and AD should confirm or rule out this possibility Awaiting further studies, the lack of significant difference between MCI and AD, which was also found for high (trkA)48 and low (p75NTR) 49 expression of nerve Inhibitors,research,lifescience,medical growth factor receptors, suggests that the transition from MCI to AD is not merely quantitative. Predictive value Another way of understanding these concepts and criteria is through their ability

to predict, the progression of patients. Follow-up studies21, 25, 36, 37, 50-59 differ in their durations, making comparisons difficult; dividing the frequency of progression toward dementia by duration of follow-up gives an estimate of the annual rates of “conversion” (Table IV). Table IV. Thus, a significant proportion of subjects did not become demented. It could Inhibitors,research,lifescience,medical be argued that a longer follow-up would increase the “conversion” rate. However, data from some studies reporting multiple evaluations21, 58, 60-62 suggest that the incidence of dementia could decrease over time. In a recent study with assessments at 3 and 6 years in subjects with CIND, aged 80 years or older,61 it was found that, according to the severity of impairment at baseline, 84% Inhibitors,research,lifescience,medical to Inhibitors,research,lifescience,medical 89% of those who were demented at

6 years had already received the diagnosis at 3 years. In another study in oldest old (84 to 90 years old at baseline) over 6 years,60 a decrease in the progression from MCI to dementia with time was also reported. ‘Ms attenuation of the rate of

progression with time could be an artifact, since in these two studies – and also in one in slightly younger subjects57 – MCI increased the risk of death by 1.758 to 760 during a 4-year period. In this case, there should be a correlation between the severity of BYL719 cognitive Inhibitors,research,lifescience,medical impairment at baseline and the risk of death. Such a trend was found in one study,58 but. not. in another,61 and in a third60 baseline performances in the deceased group were lower than those of survivors, but. higher than for those who progressed to dementia. Thus, the issue of the slope of the rate of progression deserves either further attention, particularly in relation to age at. onset, of cognitive impairment. Because the main criteria were set. to capture degenerative cognitive impairment (ie, without identifiable medical cause), an intriguing finding is that a substantial proportion of subjects were found to improve over time (4.8% after 3 years in subjects with CDR=0.563; 19.5% after 2.7 years in MCI as defined by Zaudig54; 25% after 3 years and 12% to 17% after 6 years in CIND61). In clinical practice, such an outcome would be ascribed to a diagnostic error (ie, impairment, was due to a unidentified medical condition).