Alzheimer’s disease is a neurodegenerative disorder characterized by loss of memory along with other cognitive changes, including aphasia (language impairment), apraxia (difficulty carrying out motor activities despite intact motor function), and agnosia (difficulty recognizing or identifying objects despite intact sensory function).
There is a significant impairment in social and occupational functioning, as well as a behavioral disturbance commonly occurring in the disorder that may include apathy, loss of interest in daily activities, delusions, hallucinations, preservation, disinhibition, and depression. The cognitive, functional, and behavioral components have different manifestations at different stages of the disease, and the course of the disease is characterized by gradual onset and continuing cognitive decline.
The functional change is generally hierarchical, beginning with changes in instrumental activities of daily living (using the telephone, shopping, food preparation, housekeeping, accessing transportation, taking medications, handling finances) and later affecting the basic activities of daily living (toiletting, feeding, dressing, grooming, physical ambulation, and bathing). The onset of the disorder is insidious, and the disease progresses over ten to twenty years. In the early stages the individual may require supervision or assistance for activities such as managing finances and shopping. In the later stages, 24-hour help may be required. Social skills are often preserved until the later stages, and individuals may be very impaired or be at significant risk before the disease is recognized.
The cause of Alzheimer’s disease is not understood completely. Age is the biggest risk factor, but other risk factors may be involved, including a low level of education and significant head injury. A family history of the disease also increases the risk. With familial Alzheimer’s the inheritance is autosomal dominant, and chromosomes 1, 14, 19, and 21 have been identified as important in the inheritance. It appears that individuals with the gene apolipoprotein E4 have an increased risk, while the genes apoE2 and apoE3 may have a protective function. ApoE status, however, is not considered a part of predictive testing and apoE4 is not considered a cause of the disease. The genetics of Alzheimer’s disease suggest a heterogeneous disorder, and several other genes are being investigated. Alzheimer’s disease is the most common type of dementia in older people. Prevalence estimates of dementia in Canada suggest that 8 percent of all Canadians age 65 and over have some type of dementia. Of these, 5.1 percent have Alzheimer’s disease. In the larger population, rate for Alzheimer’s disease was 1 percent in the 65 to 74 age group and 26 percent in those over 85 years. For all types of dementia the rates were 2.4 percent and 34.5 percent respectively. These rates are comparable to those found in incidence studies conducted in New York.
DIAGNOSIS AND TREATMENT
The diagnosis of Alzheimer’s disease is made by taking a history documenting the changes in capacity compared with previous abilities. It is usually necessary to obtain collateral information from a close relative or friend in order to ascertain changes, particularly in the early stages of the disorder. An individual’s general medical and surgical histories also need to be reviewed, including neurological and psychiatric histories. A complete physical examination, including a neurological examination, is imperative, along with a mental status screening test and blood work. A computed tomographic scan of the head may be helpful in some cases, particularly in patients under sixty years of age, or when there is rapid unexplained decline in cognition or function, a duration of dementia of less than two years, recent and significant head trauma, unexplained neurologic symptoms such as new onset of severe headache or seizures, and in various other instances. Other radiologic evaluations may be done, as well as certain specialized evaluations not usually part of routine clinical practice, including functional MRI and proton emission tomography (PET). Management of Alzheimer’s disease includes attention to specific problems such as safety, driving capacity, medication compliance, managing finances, and nutrition. Assistance by family members, friends, and professional persons such as lawyers and accountants can be very helpful, as can access to support services such as adult day centers and local Alzheimer’s support groups. Identifying and specifically treating depression, agitation, and sleeplessness with medication and environmental modification is also important. Judicious use of certain drugs to treat various symptoms of the disease can be undertaken as appropriate. These often include cholinesterase inhibitors such as donepezil, revistigmin, and taccine. In addition, some individuals advocate up to 2000 IU of vitamin E per day, gingko biloba, and other compounds. These therapies tend to provide symptomatic treatment and potential stabilization of the disorder for a period of time. Future therapies may include biomedical engineering for beta amyloid protein and immunization. A diagnosis of Alzheimer’s disease can be confirmed only with a brain biopsy, or through microscopical study of the brain after death. The typical lesions found include neurofibrillary tangles, senile (amyloid) plaques, and neuritic plaques. The latter is composed of a central core of homogeneous material, primarily beta amyloid, and a reactive outer zone with fibrillary and cellular material. Tau protein is the main constituent of the paired helical filaments of the neurofibrillary tangles. Other constituents include ubiquitin, a widely distributed protein. Attempts to standardize neuropathological diagnosis of Alzheimer’s disease have been undertaken by Zaben Khachaturian and by the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD). Diagnosis can be confusing because there are other disorders that cause dementia, including multiple strokes, Pick disease, Lewy body dementia, and disorders associated with other eurodegenerative diseases such as progressive palsy (PSP), Parkinson’s disease, and Huntington’s disease. Differential diagnosis is therefore an important consideration. As with many diseases, a number of ethical and legal issues are raised when dealing with those afflicted with Alzheimer’s disease. These issues revolve around questions of daily living, such as whether it is safe for an individual to drive, to continue to live at home, and to handle financial responsibilities; and around scientific questions, particularly how cognitively impaired persons can take part in research programs. Disclosing the diagnosis of Alzheimer’s disease to family members and others also causes concerns. Disclosure of the diagnosis should include a discussion of prognosis, advance planning, treatment options, support groups, and future plans.