Individual cognitive changes in subjective cognitive decline, mild cognitive impairment and Alzheimer’s disease using the reliable change index methodology

OBJECTIVE: The development of Alzheimer’s disease (AD) can be assessed using the neuropsychological test battery Vienna (NTBV). The objective of this study was to investigate whether the NTBV test scores of a diagnostic group have changed significantly over time and whether this change is due to disease progression. METHODS: In this study 358 patients referred to a memory outpatient clinic because of cognitive deterioration were analyzed. The same patients were surveyed in a follow-up assessment after a mean interval of 25.96 months to examine cognitive performance and disease progression. Patients were divided into the subgroups healthy controls (HC), subjective cognitive decline (SCD), mild cognitive impairment (MCI) and AD on the basis of the test results. Reliable change index methodology was used to assess improvement or deterioration in test scores in diagnostic groups compared to HC. RESULTS: Deterioration in the SCD group ranged from 0% to 18.8%. The MCI group showed declines between 1.6% and 29.1%. Patients who developed AD deteriorated between 0% and 54.2%. Improvements ranged from 0% to 73.4% in the SCD group and from 0% to 25.1% for the MCI group. The improvement in the AD group ranged between 0% and 44.0%. CONCLUSION: The results reflect the cognitive deterioration of patients during the disease progression. Nevertheless, improvements in diagnostic groups could be detected. The significantly positive changes might be due to practice effects, also a lack of motivation or attention in the first test could have yielded “improvement” in the retest.