Modelling mini mental state examination changes in Alzheimer's disease

The Mini Mental State Examination (MMSE) is widely used to measure dementia severity in Alzheimer's disease patients. While changes over time in the MMSE due to dementia have been studied, the relationship between MMSE scores and the duration of disease course is less well understood. Using the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) data, we modelled change in MMSE as a function of time for this population. For this purpose we used the interval between consecutive MMSE assessments as the time factor. We also investigated the impact of sex, education and age at testing on the resulting model. Analyses showed that Alzheimer's disease progression over time (ADP) can be modelled using a cubic or a logarithmic function of MMSE score. From these curves ADP can be obtained as a function of MMSE. These models demonstrate that there are different rates of change for various ranges of the MMSE. Additional analyses suggest that patient factors affect rates of ADP, younger patients and more educated patients progress more rapidly, while sex has little impact on ADP. Such estimations of disease course are useful when comparing different populations for both clinical and research purposes.