Epidemiology

Estimates have reported that up to 4 million people in the United States are currently affected by AD. Although AD is generally considered to be a disease of old age, in about 5% of the cases onset of symptoms is observed as early as 40 years. As illustrated in a community sample, the prevalence of AD dramatically increases with increasing age - about 3% of persons age 65-74 compared to nearly 50% of persons age 85 or older.³

Due to a paucity of data, the prevalence of AD in nursing home settings is largely unknown; the 1996 national Medical Expenditure Panel Study, reported over 50% of the nursing home population had a diagnosis of dementia.

Medical Conditions among Nursing Facility Residents 1996

source: Nursing Home Component of the Medical Expenditure Panel Survey (MEPS) 1996

Dementia and AD is also a global issue. Alzheimer's Disease International, (a confederation of Alzheimer's associations around the globe) reports that in the year 2000, 18 million of the world's population can be diagnosed with some type of dementia; 2/3 of the total or 12 million persons are thought to be affected by AD worldwide.

Number of persons with dementia - worldwide
Source: Alzheimer's Disease International

Due to the aging demographics of the world population, the incidence of AD is expected to dramatically increase over the next 50 years.

AD is generally believed to affect twice as many women as men. Genetic factors may be the primary mode of transmission, however, certain environmental factors may also play a role. The prevalence of AD appears to vary widely in different ethnic groups and the role of ethnic or racial factors remains unclear. A recent study reported that the age-specific prevalence of dementia, including AD, was found to be higher in Hispanic-American and African-American individuals than in Caucasians members of the sample.⁴

Level of education was strongly associated with rates of dementia and when age and education were simultaneously controlled, the ethnoracial differences in rates were not consistently found. Other researchers have reported that the risk of developing AD is higher for African-Americans and Hispanic-Americans than for Caucasians, although results are not entirely consistent. These findings are thought to represent an important area of study, because the variations in prevalence may reveal different roles for particular genetic, environmental, and metabolic factors in the development and treatment of AD across diverse populations.⁵

The course of AD is variable; survival following diagnosis of the illness ranges from 3-20 years. However, many persons are not definitively diagnosed until later in the course of the illness; average length of survival estimated from average time of diagnosis may be closer to 4-8 years. Factors predictive of earlier mortality in AD have not been clearly defined, but may include onset of extrapyramidal effects (EPS).⁶