As noted in the text, the diagnosis of probable Alzheimer's disease should be done by performing a thorough evaluation to rule out other potential causes of the observed symptoms. Based on nearly 30 years of research, new criteria were released in 2011 jointly by the National Institute on Aging and the Alzheimer's Association.

These new criteria created considerable controversy. Research indicated that Alzheimer's disease progresses through a series of stages, from a "preclinical" phase in which no symptoms can be easily detected, through mild cognitive impairment, to clinical Alzheimer's disease (Albert et al., 2011; Jack et al., 2011; McKhann et al., 2011; Sperling et al., 2011).

In addition, the criteria included a call for biomarkers to be linked with the various categories, as well as new standards for brain autopsy. The main controversy concerned whether people should be diagnosed with a "preclinical" form of Alzheimer's disease, especially when there is no treatment and many people never go on to develop clinical Alzheimer's disease (Brickman, 2011).

Research has shown that abnormal levels of beta-amyloid protein are associated with mild cognitive impairment (Rodrigue, Kennedy, & Park, 2009), but again, whether everyone with high levels of amyloid should have a diagnosis is controversial (Brickman, 2011).

However, the recent research linking tau protein transmission across neurons offers hope that a drug or other effective therapy could be invented to prevent such transmission (Liu et al., 2012).

Despite the controversies, the new criteria make clear that the link between research and clinical application needs to be a strong one. Clear evidence of specific behaviors or health markers needs to be present. You should ensure that this is the case for anyone in your family or in your work.

1. What are the primary reasons why the diagnosis of Alzheimer's disease in the "preclinical" phase is seen as controversial?

2. If you were an older adult and were suffering from a condition for which there was no cure and very few treatment options, would you want to know about the disease or would you want your doctor and family to keep this information from you? Explain your choice.

3. What biological markers have been found that might indicate the presence of Alzheimer's disease in a human being?

4. Exactly what does it mean to say that a person is in the "preclinical phase" of Alzheimer's disease? What implications does this have for the progression of the illness?