Alzheimer's disease (AD) is the most common adult onset neurodegenerative disorder and accounts for up to 60% of all age-related cases of dementia in Western societies (Woodruff-Pak & Papka, 1999). The disease is characterized by a progressive decline in cognitive abilities, personality, and psychomotor functioning over a period averaging from 8 to 10 years (Filley, 1995; Morris, 1994). Memory impairment is the principal feature of AD and several distinct stages of the disease, often classified as mild, moderate, and severe, are recognized (Morris, 1994). Early manifestations of the disease include the inability to recall recent events, difficulties with word-finding, and geographic or temporal disorientation. As memory loss grows over the course of the disease, the individual's ability to carry out even simple routine activities is affected, language output and comprehension decline, and behavioral problems, such as wandering and restlessness, aggression, and suspiciousness appear. In advanced AD, the affected individual is totally functionally dependent due to severe dementia, and is typically mute and incontinent.
Diagnosis. Definitive diagnosis of AD requires cerebral biopsy or postmortem examination. Neuro-pathological changes associated with AD include loss of neurons in the medial temporal and frontal cortices, neu-ritic plaques and neurofibrillary tangles, and B-amyloid deposits (Franklin & Nelson, 1998). A decrease in the neurotransmitter acetylcholine has also been correlated with decline in memory and cognition in AD. Clinical criteria for the differential diagnosis of probable AD include progressive deficits in memory and other cognitive functions or personality that are sufficient to interfere with the person's ability to conduct usual daily activities in the absence of any other systemic or brain diseases (Morris, 1994). These deficits are identified through neurologic examination, brain imaging, and neuropsychological testing (Filley, 1995). Considerable methodologic work has been done on the development of culturally appropriate diagnostic instruments for AD (e.g., Chandra, Ganguli, Ratcliff et al., 1998).
Research on AD suggests a complex etiology involving interactions of biological and genetic variables with a range of environmental and lifestyle exposures (Radebaugh, Buckholtz, & Khachaturian 1996). Age is the most widely recognized risk factor for AD: the prevalence and incidence of AD increase with age in all populations in which it has been investigated. Varying prevalence rates for dementia among older adults have been reported for North American, European, and Asian populations with estimates ranging from 2% to 11% in persons aged 65 and over and 30%-50% in those aged 85 and over (Larson & Imai, 1996). These populations differ, moreover, in the relative proportions of AD and vascular dementia. Among the Western, predominantly Caucasian study populations, between 50% and 70% of the rate in attributed to AD and 12%-20% to vascular disease (Graves et al., 1996). Most studies of Asian populations, on the other hand, have ascribed between 30% and 60% of dementia cases to vascular disease, and approximately 15%—30% to AD (Graves et al., 1996). Information about the incidence of AD worldwide is generally limited (Roca, 1994).
A confirmed genetic risk factor for AD in some populations is the E-4 allelle of the gene for apolipopro-tein E (APOE), a serum cholesterol carrier protein which has been associated with increased B-amyloid deposition. APOE4 has been associated with early-onset AD and with both sporadic and familial forms of late-onset AD.
The distribution of the APOE4 allelle has been shown to vary both within and among populations (Kalaria et al., 1997; Pericak-Vance et al., 1996). A comparison of APOE4 frequencies in various developed and African countries showed relatively high frequencies in African populations (up to 37% in South African Bushmen) compared with Caucasian American, European, and Asian populations (Kalaria et al., 1997). In addition, the effect of the allelle may vary across environments. Relatively high frequencies of APOE4 were found among elderly non-demented East Africans, for example (Kalaria et al., 1997). A number of cross-cultural epidemiologic studies aimed at disentangling genetic and environmental risk factors for AD are currently underway (Chandra, Ganguli, Pandav et al., 1998; Hendrie et al., 1995; White et al., 1996). A study of the incidence of AD in persons aged 65 and over of common genetic heritage—African Americans in Indiana and Africans in Ibadan, Nigeria (Hendrie et al., 2001) revealed higher rates of dementia, including AD, among the former than the latter. In addition, there was only a marginally significant association between AD and APOE4 among the African Americans, and no significant association between the gene and the disease among the Africans.
Other possible risk factors that have been evaluated for their association with AD include head trauma with a loss of consciousness, history of depression, family history of certain disorders (dementia, Down's syndrome, Parkinson's disease), low level of education, late maternal age, hypothyroidism, and environmental exposure to toxins (Roca, 1994). A definitive list of risk factors for AD remains to be established, however, and the relationship of many of these risk factors with AD in non-Western populations has yet to be investigated.
Prevention and Treatment. Currently, curative treatment is not available for AD. A number of drugs designed to enhance cholenergic function, however, have been successful in producing a temporary slowing in cognitive decline with an improvement of behavioral symptoms in some patients with early AD (Giacobini, 2000). Three of these cholinesterase inhibitors, tacrine, rivastigmine, and donepezil, are currently registered for use in the United States and Europe. Estrogen, which also affects several neurotransmitter systems, is thought to improve cognitive function in women with AD, although findings on its ability to prevent or delay AD are still inconclusive (Hirai, 2000). Based on the observation that patients with rheumatoid arthritis have a very low prevalence of AD, non-steroidal anti-inflammatory drugs are being evaluated for their effectiveness against AD in which areas of the brain most affected by neurodegenerative changes also show evidence of inflammation (Hirai, 2000). Various antioxidants, such as Vitamin E and ginkgo biloba, a herbal extract with effects on cholinergic function, are used as complementary medical treatments for memory problems, and have been shown to have modest efficacy in slowing the progression of cognitive symptoms (LeBars, Kieser, & Itil, 2000; Mix & Crews, 2000; Wettstein, 2000). Future treatment modalities for AD will likely involve combining several of these pharmaco-therapies (Giacobini, 2000).
Sociocultural Studies of Alzheimer's Disease.
The sociocultural context of AD has been investigated from several perspectives. A social constructionist framework has been used in a number of studies (Chatterji, 1998; Gubrium, 1986, 1987, 1991; Saunders, 1998; Vittoria, 1999) to examine the processes of identity maintenance in older adults with dementia by the patients themselves, by health care providers, and by family care-givers. Variations in ethnomedical beliefs about the causation of AD have also been documented among different groups within the United States (Elliott, DiMinno, Lam, & Tu, 1996; Henderson, 1989; Olson, 1999). Beliefs about dementia prevalent among traditionally oriented Chinese Americans, for example, include the interpretation of dementia as retribution for the sins of one's ancestors, spirit possession, fate, an imbalance of energy within the body, or the lack of proper orientation of important physical sites and objects with the forces of nature (Elliott et al., 1996). Henderson (1987) has also considered how the sociocultural environment in which AD exists in contemporary America acts to generate or exacerbate illness problems and how these problems are culturally managed. He discusses AD support groups as fictive kinship forms that have emerged to provide assistance to members faced with an acute care medical care system and a nuclear family kinship system that are unable to meet the needs of elders with a chronic, debilitating brain disease.
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