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Predicting Who Gets Alzheimer's Disease Using Mild Cognitive Impairment Tests

   In the past few years, there has been a great deal of new research that has been focused on predicting who will eventually develop alzheimer's disease. The new research has focused on a concept called MCI, mild cognitive impairment. Basically, research has been looking at elderly people who are relatively normal but have some mild memory problems to see what factors in their history make them later develop alzheimer's disease. If people can be identified before they develop alzheimer's disease, drugs and other new therapies may delay the progression to full blown alzheimer's disease.... at least that is the hope of the new research.
    There are specific guidelines that are used to decide if someone has mild cognitive impairment. First, the person with suspected MCI must feel that they have problems with memory. In addition, family and friends also see evidence of memory loss as they relate to that person during every day life. A person with MCI doesn't have problems with thinking, speech or problems doing routine financial things, such as writing checks. Persons with MCI also have full ability to manage their daily activities of daily living, such as bathing, dressing and eating. The last guideline for MCI diagnosis is that the person has no other medical, neurologic or psychiatric illness to account for the subjective memory loss.
   The diagnosis of MCI has been very useful to date. It has been found that among people who meet the guidelines for MCI, almost 50 percent will eventually develop alzheimer's disease within 3 to 5 years[1]. Still, not everyone with MCI develops alzheimer's disease. One study found that 25 percent of MCI cases do not progress to alzheimer's disease, even after 10 years of memory problems [2]. Of those MCI cases who do progress to alzheimer's disease, more than 60 percent have a history of depressive illness along with memory impairment[3]. A history of depressive illness significantly increases the risk for alzheimer's disease. A more comprehensive look at depression as a risk factor for alzheimer's disease can be found by clicking this link. Depression And Alzheimer's Disease.
    The most useful way of diagnosing MCI is to ask the person directly if they have memory difficulties (called self-reported memory loss) or to ask friends and family if the person they live with has memory difficulties (called informant-reported memory loss). A new test, called the Alzheimer's Questionnaire (AQ), has been successfuly used to diagnose MCI. The test is given by a physician in the office and involves asking friends and family about memory loss in their loved one. The test diagnoses MCI with 94 percent specificity [4]. A recent study found that four questions on the AQ best predict who has MCI [5]...
    Weight loss may be an additional indicator of who develops alzheimer's disease. A large number of people were followed from 1972 to 1993 in the Rancho Bernardo Study [6]. This study found that people who developed alzheimer's disease lost weight before they were diagnosed with the disease. Comparable elderly people who remained free of alzheimer's disease never lost weight, but remained stable or gained weight. Another study found that an acceleration of weight loss in an elderly person is also linked to developing alzheimer's disease earlier on [7]. Another study found that patients who develop alzheimer's disease have already lost a significant amount of weight 4 to 6 years before they are diagnosed with alzheimer's disease [8]. My father was diagnosed in 1990 with alzheimer's disease, but the year before he was diagnosed, he lost more than 30 pounds, despite being healthy and eating normally. For my dad, weight loss was the earliest sign of alzheimer's disease, even before he developed memory problems. The reason for early weight loss in patients who later develop alzheimer's disease is not yet known.
    There have been many studies using biomarkers to predict when MCI converts to alzheimer's disease. MRI scans have been done on people with MCI, and those MCI patients who later develop alzheimer's disease tend to have reduced brain areas in the hippocampus, an area of the brain important to memory [9]. The trouble with MRI scans is that they are only partially predictive of MCI conversion to alzheimer's disease. A master study has found that reports of memory complaints are better predictors than MRI scans of who goes on to develop alzheimer's disease [10].
    An interesting new biomarker for MCI conversion to alzheimer's disease has been found by checking cerebrospinal fluid. People who have MCI and later develop alzheimer's disease tend to have reduced levels of amyloid beta and increased levels of phosphorylated tau in their spinal fluids. More than 100 studies have validated this finding. The combination of the two indicators successfully identifies those without alzheimer's disease from those with alzheimer's disease with 85 percent accuracy. The combination of the two indicators in spinal fluid successfully predicts, with 90 percent accuracy, persons with MCI who later develop alzheimer's disease [11].


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