The boundaries of Alzheimer’s disease

Psychiatric News, March 23, 2012

Mild cognitive impairment is a condition that can turn into Alzheimer’s disease, but determining the borderline between these two conditions makes the diagnosis all the more complex.

How do we determine whether individuals of advanced age who have develop memory impairment, should be diagnosed with mild cognitive impairment (MCI) or with early stage Alzheimer’s disease?

A few months ago, with the recommendation of the American National Institute on Aging, and the Alzheimer’s Association, Alzheimer’s specialists published a guideline, hoping that it will help clinicians to answer this question.

Director of the Washington University Alzheimer’s Research Centre Dr. John Morris, who is one of the Alzheimer’s specialists who did not take part in the preparation of these guidelines, made the accusation that the guidelines made it even more difficult to differentiate between MCI and the early stages of Alzheimer’s disease. Dr. Morris shared his views in an interview made in February with the journal Archives of Neurology.

Dr. Morris supports his objections with a study he undertook. The study involved 18,000 patients from 33 different Alzheimer’s centres supported by Federal funds. The group subject to the study consisted of patients that were diagnosed before the new guidelines came into effect. The patients in the group all had normal cognitively functions, and were grouped as MCI patients and Alzheimer’s patients. Dr. Morris then assessed these patients according to the new guidelines.

On the basis of the main elements of the assessment scale for the Clinical Grading of Dementia, which measures the functional ability of the patient both in a social environment and home environment, Dr. Morris established that according to the new guidelines, most of the patients diagnosed with mild Alzheimer’s, would come under the category of MCI.

The scale of the Clinical Grading of Dementia assesses patients according to their abilities in shopping, preparing food, managing financial transactions like banking activities, and functional abilities like driving a car. Dr. Morris states that an individual with mild deterioration in any of these functions was previously diagnosed with early stage Alzheimer’s, that however according to the new guidelines, patients who experience such difficulties are no longer diagnosed with Alzheimer’s but with MCI. “In conclusion, with the new criteria the categorical difference between MCI and mild stages of Alzheimer’s disease will disappears”, he concludes.

Dr. Morris claims that “removing this functionality-based borderline between MCI and Alzheimer’s will have the result that the differentiation between these two conditions will be made on the basis of the clinician’s individual opinion”, and that “this can even lead to a non-standard and arbitrary approach in the diagnosis of MCI.” He states that such arbitrary approach will bring additional difficulties to clinical research that aims at assessing the progression from MCI to Alzheimer’s disease and will adversely affect such research.

And what is the response of the Alzheimer’s Specialists who prepared the guidelines, to Dr. Morris’ accusations?

Ronald Peterson, a medical doctor who is leading the Alzheimer’s Research Centre of the Mayo Clinic, stated the following in an interview he gave to Psychiatric News: “I do not believe that the new guidelines weaken the differentiation between MCI and Alzheimer’s disease. Dr. Morris ignores the fact that the criteria applicable to MCI already contains the condition to explicitly exclude a diagnosis of dementia. Because he ignores the criteria applicable to MCI and only uses the grading scale of the Dementia Clinic, his data analysing process is already an approach without a basis. Furthermore, the scale for the Clinical Grading of Dementia was developed in the 1970’s long before the expression MCI was introduced, and aimed at differentiating between Alzheimer’s and a normal condition.”

Dr. Reisa Sperling, Associate Professor in Neurology at the Harvard Medical Faculty, stated in an interview he gave to Psychiatric News, that “it is a very delicate task to tell apart MCI from early stage Alzheimer’s”. “I share Dr. Morris’ opinion on classifying Alzheimer’s in the preclinical stage. This is the field of interest of the study group I lead. Dr. Morris claims that there should only be two categories – preclinical period (the pre-symptomatic period) and the symptomatic period.”

The study in question was supported by the American National Institute on Aging and the National Alzheimer’s Coordinating Centre.