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ALZHEIMER’S DISEASE Alzheimer’s disease is a progressive, neurodegenerative disease which is caused by physiological changes

admin2011-02-08  9
问题                  ALZHEIMER’S DISEASE
    Alzheimer’s disease is a progressive, neurodegenerative disease which is caused by physiological changes to the brain. It changes the delicate organisation of the nerve cells in the brain by creating the gradual spread of sticky plaques and clumps of tangled fibres. As brain cells stop communicating with each other, they atrophy, causing memory and reasoning to fade. Tangles and plaques first appear in the entorhinal cortex, an essential memory-processing centre needed for creating memories and retrieving old ones. This does not affect detailed complex memories, but rather the simple recollections of facts that allow us to function socially, such as birthdays and lunch dates. Over time they move higher, invading the hippocampus, that part of the brain that forms complex memories of events or objects. These kinds of memories are, of necessity, more detailed and involve longer recollections. It allows us to recall how to function at work and complete reasonably complex tasks but without the need to analyse or make judgements. Finally, the tangles and plaques reach the top of the brain or the neocortex, the executive that sorts through stimuli and orchestrates behaviour. Here, amongst other functions, we are using analytical skills to evaluate, digest and respond to situations appropriately.

    The onset of the disease is characterised by an initial memory decline and, over several years, it destroys cognition, personality and the ability to function, but preserves motor function. Confusion and restlessness may also occur. It is a progressive disease and the type, severity, sequence and progression of any mental changes that occur vary widely, The early symptoms of Alzheimer’s which include forgetfulness and loss of concentration, can easily be missed because they resemble the natural signs of aging. Similar symptoms can also result from fatigue, grief, depression, illness, vision or hearing loss, the use of alcohol or certain medications, or simply the burden of too many details to remember at once. A cure is not imminent; there is no way to deter the progression of the disease and its precise cause is largely mysterious. On average, 10% of people over 65 will contract Alzheimer’s disease, a number that rises to 50% by the age of 80. Its onset may occur as early as the age of 40. Approximately 100,000 victims die and 360,000 new cases of Alzheimer’s disease are diagnosed each year. It is estimated that by the year 2050, 14 million Americans will have this disease.
    Much current knowledge about this illness comes from a single piece of ongoing research: The Nun Study. Since 1986, David Snowdon, a scientist from the University of Kentucky, has been studying 678 School Sisters. To Snowdon, this group of elderly women represented an ideal population for studying the disease: their economic status, health care and living conditions are uniform with fewer variations in lifestyle to confound the data. Of course, the very homogeneity of this population means Snowdon’s study has its detractors-for example, the nuns face few of the stresses of modern life, nor do they smoke or drink. Some of the factors that lead to Alzheimer’s disease may not be present in their lives. But whatever the limits, Dr. Snowdon’s study has achieved a 68% compliance rate among the sisters in that religious community, and continues after death with post-mortem examinations of their brains, and thus promising much valuable information. Over the years, Snowdon and his colleagues have discovered a series of unexpected links between lifestyle and Alzheimer’s disease. It has been known for some time that genes can predispose people to Alzheimer’s disease, but Snowdon’s study has shown that other factors play an important part in the development of this dreadful disease.
    Some of the results of the study have been widely publicised. The study found that those nuns whose early autobiographies contained complex grammar and a greater density of ideas had the lowest risk of developing Alzheimer’s disease. This result that isolates complexity in writing as a protector against Alzheimer’s disease suggests a correlation between higher brain capacity and lowered risk. Preliminary studies also seemed to indicate that those nuns whose early autobiographies suggested a predisposition to negative emotions had a higher risk of Alzheimer’s disease than those who were more optimistic in the way they conveyed their written ideas. Other important findings of the study include the fact that stroke increases the risk of Alzheimer’s disease. Evidence of stroke, including those undiagnosed before death, as well as earlier brain trauma, as from head injury, was more prevalent in those nuns who died of Alzheimer’s disease than in those who died without that diagnosis. Dr. Snowdon’s research also confirms the suspicion that folate deficiency might contribute to Alzheimer’s disease. High folate levels appear to have been protective in these nuns. This ties in with other studies which have shown that folic acid deficiency plays a role in some forms of mental retardation in children and in some cognitive problems in adults.
    New research is showing that the decline in cognitive function may start sooner than previously thought. Scientists suggest that a condition known as mild cognitive impairment, in which patients in their forties and fifties exhibit memory and recall problems, is very likely the first step along the way to Alzheimer’s disease. If so, then it is important to start slowdown strategies as soon as possible.
    Glossary:
    The entorhinal cortex, the hippocampus and the neocortex are those parts of the brain that are primarily affected by Alzheimer s disease.
    plaque—fibre-like substance which multiplies in the brain of Alzheimer’s sufferers.
    folate—is water-soluble vitamin B occurring naturally in foods such as leafy green vegetables, some fortified cereals and grain products.
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答案genetic predisposition
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