Alzheimer's Disease (AD) is a progressive degenerative disease of unknown aetiology, as first described by Alois Alzheimer (19
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Alzheimer's Disease (AD) is a progressive degenerative disease of unknown aetiology, as first described by Alois Alzheimer (1907). According to Shoenberg et. al (1987), it is the commonest cause of dementia in the elderly with an incidence ranging from 2.5 to 5 per thousand. Furthermore, this incidence has grown in recent years as a result people generally living longer. The disease is incurable at present but there are drug treatments that delay the symptoms in the early stages. Therefore, there is a real need for early identification of the disease, so that a treatment program can be administered. In the later stages of AD, there are typical neurological signs of the disease. These are plaques and tangles in the hippocampal region of the brain. However, it may be a while into the disease before these can be detected by diagnostic tools such as CT, MRI and fMRI. In addition, reliance on these tools can lead to a false diagnosis of AD, where some form of vascular dementia is actually the cause. In fact, according to Brazzelli et al. (1994), there is no unequivocal instrumental test to establish the presence of the disease. Therefore, it is also common practice to establish the neuropsychological symptoms of AD. Numerous studies have been conducted into the neuropsychiatric symptoms of AD so that diagnosis can be as accurate as possible. According to Venneri, Turnbull and Sala (1996) the low contribution of neurological and neuroradiological examination to the diagnosis of AD in its early stages raises severe diagnostic problems.
It is also interesting because the patients in this study were in the early stages of illness. As discussed earlier, it is important to identify early characteristics of AD for appropriate diagnosis and prognosis of the patient. This possible subtype of AD would also allow for a clearer distinction between AD and dementia with lewy bodies (where hallucinations are a major characteristic). A later paper by Sultzer et. al (2003), looked into the relationship of AD with psychosis and regional cortical metabolism in patients with AD. The study involved conducting PET scans on 25 patients with probable AD (not on psychotropic medication). The severity of the delusions was assessed using a semi-structured interview and the Neurobehavioral Rating Scale. The findings indicated that the severity of delusions was associated with hypometabolism in additional prefrontal and anterior cingulated regions. Although this research is useful in determining a link between the psychosis syndrome and regional brain functioning, there are methodological problems. Firstly, the study focused on metabolic rates in certain regions of the brain, on the basis on previous findings. This meant that associations between the severity of delusions and metabolic activity elsewhere in the brain. Additionally the limited number of participants limited the number of effects that could be observed. Finally, it could not be determined whether regional metabolic rates are a cause or an effect of delusional thoughts in AD. A study in the same year (Cook et al., 2003) looked at psychotic symptoms in AD to investigate whether AD with psychosis was homogenous or a composite of subtypes.
The increase was independent of dementia severity. It was suggested that some common underlying process or processes specific to AD might regulate both phenomena (i.e. neurofibrillary tangles and psychosis). However further investigation is needed to see if this is a common occurrence in AD patients and to determine is there is a causal relationship between the two phenomena. It is difficult to investigate this as the patient must be deceased for investigation such as this to be carried out. Furthermore, it may be interesting to see whether this effect occurs cross-culturally. According to Chow et. al (2002) the prevalence of Alzheimer's disease is similar across ethnic groups. However, they also state that there have been few cross-cultural studies into behavioural symptoms. The study compared neuropsychiatric symptoms of Chinese and American patients with AD. It was found that caregivers of the Chinese samples reported more anxiety and delusions than Americans. The caregivers of the Americans reported more appetite changes and apathy than the Chinese. This shows that there are behavioural differences in AD cross-culturally. Overall, these studies show that there is still much need for further study into the neuropsychiatric symptoms of Alzheimer's disease. The current studies show that there are important symptoms that may warrant a change in criteria for AD to incorporate additional subtypes. However, the problems that the current studies have faced include relying on previous work, limited selection of participants and reliance on post-mortem for confirmation. Future studies might benefit from using cross-cultural studies and longitudinal observations from representatives samples. From this, a better understanding of AD can be established delivering a better prognosis for the sufferers.
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