dementias —Î_Miscellaneous dementias



FIGURE 5 Percentage of major forms of dementias in the elderly. Abbreviations: DLB, Lewy-body dementias; VaD, vascular dementias.

It is important to recognize that dementia is not an inevitable consequence of aging; the greater proportion of the elderly remains lucid and mentally competent until death. One study showed that, in l982, severe dementia affected only 4% to 5% of those aged 65 years and older and 10% of these patients were affected by mild-to-moderate forms. The incidence (that is, the number of newly diagnosed cases in a certain time interval) of severe dementia rises dramatically with age. Likewise, the prevalence (that is, the number of cases of a disease existing for a given population and at a given time) also increases with old age, doubling with each subsequent five-year interval from about 1% at ages 65 to 70 to 20% to 50% at ages 85 or older. However, when the prevalence of dementia is compared at selected intervals (1982, 1988, 1994, and 1999) (Box 3), these percentages, of the same age groups, show a significant decline (104-107). Age and family history are the most important risk factors for dementia in older populations. Although some studies seem to indicate a slight decline in AD after age 90, it is still unknown why, exactly, after age 90, other diseases become more common than AD. Recent studies show, in the United States, an increase in AD as cause of death in the 85 + age group from 1996 (1.9%) to 2003 (5.5%) (Chapter 3, Table 13).

The relatively young age of the patient (51 years of age), a woman, first described by Alzheimer, indicates that AD may also occur at younger ages than those so far discussed. Usually, those individuals diagnosed with the "early-onset" form of AD (40-50 years) present the same symptoms and pathology as those diagnosed with the "late-onset" form (65 years and older), but their symptoms are generally more severe, and the disease progresses more rapidly. Considerable genetic research with AD presently involves these familial early-onset cases.

About two-thirds of the patients in nursing homes have dementia; therefore, two-thirds of the enormous amount of money spent in nursing home care in the United States each year (many billions of dollars) is expended on patients with dementia. Each year, several hundred thousand Americans develop the disease, and at least a hundred thousand die with it. Presently, according to the AD Association, there are, in the United States, more than 4 million patients with AD, with an estimate as high as 14 million over the next 30 years, an estimate considered quite conservative by many. In 2003, in the United States, AD complications (e.g., pneumonia, falls, and accidents) represented the fourth leading cause of death within the 85 + age group (Chapter 3). Probably more so than other chronic diseases, the demented state leads to other morbid conditions that represent the immediate cause of death. The problem of care for demented patients is a serious one; it represents a significant burden for individual caretakers, health-care resources, and society at large (Box 4).

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