A comment on age at onset as a subtype of Alzheimer disease

Subtypes of Alzheimer disease (AD) can be approached from different ways. An intuitive and commonly proposed subtype relates to the age at onset of disease. Research on age at onset as a subtype has yielded conflicting results that may, in part, reflect different measurement approaches. Refinement of the measurement of change in AD should yield a clearer picture of subtypes, as would closer ties between neuropathologic and clinical work. Thus, it is suggested that future research should use measurement techniques that more closely characterize AD than do current approaches. In addition, progress would likely be through attempts to link clinical findings regarding rates of change to neuropathologic findings.