A new hypothesis (concept) of diagnosing Alzheimer's disease

The diagnosis of dementia has proven problematic due to different criteria. Even neuropathological changes are arbitrarily defined. A mathematical model is proposed that may standardize diagnosis of dementia, and Alzheimer's disease was used as an example. The model suggests that there are cognitive decline curves that represent the rate of natural attrition for neurons in the cerebral cortex. In normal aging, each individual will lose neurons along one curve. Individuals with higher brain reserve will start off at a higher percentile. An accelerated loss of neurons (dementia) is depicted as a deviation from the natural cognitive decline curve. This model may differentiate age-related cognitive decline from dementia or preclinical dementia. Furthermore, it may allow dementia to be diagnosed earlier, hence earlier treatment. Comparison of data may be easier and more valid if the diagnosis of dementia is standardized under this model. Advantages and challenges of this concept are further discussed.