Background: The cognitive continuum in the elderly population can be conceptually divided into those who are functioning normally (control subjects), those with a mild cognitive impairment (MCI), and those with probable AD.
Objectives: To test the hypothesis that the annualized rates of hippocampal atrophy differ as a function of both baseline and change in clinical group membership (control, MCI, or AD).
Methods: The authors identified 129 subjects from the Mayo Clinic AD Research Center/AD Patient Registry who met established criteria for normal control subjects, MCI, or probable AD, both at entry and at the time of a subsequent clinical follow-up evaluation 3 +/- 1 years later. Each subject underwent an MRI examination of the head at the time of the initial assessment and at follow-up clinical assessment; the annualized percentage change in hippocampal volume was computed. Subjects who were classified as controls or patients with MCI at baseline could either remain cognitively stable or could decline to a lower functioning group over the period of observation.
Results: The annualized rates of hippocampal volume loss for each of the three initial clinical groups decreased progressively in the following order: AD > MC > control. Within the control and MCI groups, those who declined had a significantly greater rate of volume loss than those who remained clinically stable. The mean annualized rates of hippocampal atrophy by follow-up clinical group were: control-stable 1.73%, control-decliner 2.81%, MCI-stable 2.55%, MCI-decliner 3.69%, AD 3. 5%.
Conclusion: Rates of hippocampal atrophy match both baseline cognitive status and the change in cognitive status over time in elderly persons who lie along the cognitive continuum from normal to MCI to AD.