Our data suggest that there is a continuum of cognitive change accompanied by gradual accumulation of neuropathology with no precise clinical or neuropathologic cut-point that distinguishes dementia from MCI or MCI from normality. This is similar to many other common chronic conditions of aging such as osteoporosis and chronic obstructive pulmonary disease. These diseases have an insidious onset over years and possibly decades and the demarcation between the presence and absence of the disease is determined by consensus criteria based on imperfect data. For some conditions, a designation of intermediate between normality and disease is employed, as in pre-hypertension and osteopenia. This is analogous to the use of MCI as a condition intermediate between normality and dementia. Overall, the data suggest that much of cognitive decline among persons without dementia is not the result of a normative aging process but rather the result of the common neuropathologies that ultimately result in MCI and dementia [198]. This conclusion is consistent with reports that AD pathology is common among persons with MCI [199–202] and some report AD pathology among persons without cognitive
